© 2026 Bryan R. Hinton. All rights reserved. All original text, photographs, and processed imagery published here, including hyperspectral reconstructions, abundance maps, classification maps, anomaly maps, and any other algorithmically derived visualizations, are the intellectual property of Bryan R. Hinton. The underlying spectral data, latent representations, and intermediate pipeline outputs are likewise reserved. Archival documents reproduced on the site (e.g. scans held by the Nationaal Archief, Den Haag, or other public repositories) remain in the public domain or under their original licensing; only the accompanying captions, commentary, and any derivative analysis are © Bryan R. Hinton. No portion of the copyrighted material above may be reproduced, redistributed, modified, displayed, or used to train, fine tune, or evaluate machine learning models without prior written permission. Brief quotation for the purposes of criticism, scholarship, or review is permitted under standard fair use principles, provided attribution is given.

A hardware design for variable output frequency using an n-bit counter

The DE1-SoC from Terasic is an excellent board for hardware design and prototyping. The following VHDL process is from a hardware design created for the Terasic DE1-SoC FPGA. The ten switches and four buttons on the FPGA are used as an n-bit counter with an adjustable multiplier to increase the output frequency of one or more output pins at a 50% duty cycle.

As the switches are moved or the buttons are pressed, the seven-segment display is updated to reflect the numeric output frequency, and the output pin(s) are driven at the desired frequency. The onboard clock runs at 50MHz, and the signal on the output pins is set on the rising edge of the clock input signal (positive edge-triggered). At 50MHz, the output pins can be toggled at a maximum rate of 50 million cycles per second or 25 million rising edges of the clock per second. An LED attached to one of the output pins would blink 25 million times per second, not recognizable to the human eye. The persistence of vision, which is the time the human eye retains an image after it disappears from view, is approximately 1/16th of a second. Therefore, an LED blinking at 25 million times per second would appear as a continuous light to the human eye.

scaler <= compute_prescaler((to_integer(unsigned( SW )))*scaler_mlt);
gpiopulse_process : process(CLOCK_50, KEY(0))
begin
    if (KEY(0) = '0') then  -- async reset
        count <= 0;
    elsif rising_edge(CLOCK_50) then
        if (count = scaler - 1) then
            state <= not state;
            count <= 0;
        elsif (count = clk50divider) then -- auto reset
            count <= 0;
        else
            count <= count + 1;
        end if;
    end if;
end process gpiopulse_process;

The scaler signal is calculated using the compute_prescaler function, which takes the value of a switch (SW) as an input, multiplies it with a multiplier (scaler_mlt), and then converts it to an integer using to_integer. This scaler signal is used to control the frequency of the pulse signal generated on the output pin.

The gpiopulse_process process is triggered by a rising edge of the CLOCK_50 signal and a push-button (KEY(0)) press. It includes an asynchronous reset when KEY(0) is pressed.

The count signal is incremented on each rising edge of the CLOCK_50 signal until it reaches the value of scaler - 1. When this happens, the state signal is inverted and count is reset to 0. If count reaches the value of clk50divider, it is also reset to 0.

Overall, this code generates a pulse signal with a frequency controlled by the value of a switch and a multiplier, which is generated on a specific output pin of the FPGA board. The pulse signal is toggled between two states at a frequency determined by the scaler signal.

It is important to note that concurrent statements within an architecture are executed concurrently, meaning that they are evaluated concurrently and in no particular order. However, the sequential statements within a process are executed sequentially, meaning that they are evaluated in order, one at a time. Processes themselves are executed concurrently with other processes, and each process has its own execution context.

Creating stronger keys for OpenSSH and GPG

Create Ed25519 SSH keypair (supported in OpenSSH 6.5+). Parameters are as follows:

-o save in new format
-a 128 for 128 kdf (key derivation function) rounds
-t ed25519 for type of key

ssh-keygen -o -a 128 -t ed25519 -f .ssh/ed25519-$(date '+%m-%d-%Y') -C ed25519-$(date '+%m-%d-%Y')

Create Ed448-Goldilocks GPG master key and sub keys.

# gpg --quick-generate-key ed448-master-key-$(date '+%m-%d-%Y') ed448 sign 0
# gpg --list-keys --with-colons "ed448-master-key-08-03-2021" | grep fpr
# gpg --quick-add-key "$fpr" cv448 encr 2y
# gpg --quick-add-key "$fpr" ed448 auth 2y
# gpg --quick-add-key "$fpr" ed448 sign 2y

96Boards - JTAG and serial UART configuration for ARM powered, single-board computers

The 96boards CE specification calls for an optional JTAG connection. The specification also indicates that the optional JTAG connection shall use a 10 pin through hole, .05" (1.27mm) pitch JTAG connector. The part is readily available on most electronics sites. Breaking out the pins with long wires and shrink wrapping them is ideal for making sure that each connection is labeled and separate when connecting to a JTAG debugger. While a JTAG connection is not required for flashing or loading the bootloaders onto the board, the JTAG connection is useful for advanced chip-level debugging. The serial UART connection is sufficient for loading release or debug versions of bl0, bl1, bl2, bl31, bl32, the kernel, and userspace.  Last but not least, ARM-powered boards, with 12V power input, often require external fans to keep the board cool. As seen in the below photos, two 5V fans were powered from an external power supply. Any work on microcontroller boards should be performed on a grounded surface.  Proper grounding procedures should always be followed as most microcontroller boards contain ESD sensitive components.

In the below photos, a 96Boards SBC is mounted on an IP65, ABS plastic junction box for durability. The pins are extended and mounted with screws underneath the junction box. The electrical conduit holes on the side of the junction box are ideal for holding small, project fans. The remaining electrical conduit holes provide a clean place to place the remaining wires from the board - micro USB, USB-C, and 12V power.

HiKey 960 Linux Bridged Firewall

The Kirin 960 SoC and on-board USB 3.0 make the HiKey 960 SBC an ideal platform for running a Linux Bridged firewall. The number of single-board computers with an SoC as powerful as the HiSilicon Kirin 960 are limited.

When compared with the Raspberry Pi series of single board computers (SBC), the HiKey 960 SBC is significantly more powerful. The Kirin 960 also stands above the ARM powered SoCs which reside in most commercial routers.

USB 3.0 makes the HiKey 960 board an attractive option for bridging or routing, filtering network traffic, or connecting to an external gateway via IPSec. Both network traffic filtering and IPSec tunneling can be computationally expensive operations. However; the multicore Kirin 960 is well suited for these types of tasks.

In order to be able to run an IPSec client tunnel and a Linux Bridged firewall connected over 1G ethernet links, certain kernel configuration modifications are needed. Furthermore, the Android Linux kernel for the HiKey 960 board does not boot on a standard Linux root filesystem because it is designed to boot an Android customized rootfs.

The latest googlesource Linux kernel (hikey-linaro-4.9) for Android (designed to boot Android on the HiKey 960 board) has been customized to remove the Android specific components so that the kernel boots on a standard Linux root filesystem, with the proper drivers enabled for network connectivity via attached 1000Mb/s USB 3.0 to ethernet adapters. The standard UART interface on the board should be used for serial connectivity and shell access. WiFi and Bluetooth have been removed from the kernel configuration. The kernel should be booted off of a microSDHC UHS-I card. The 96boards instructions should be followed for configuring the HiKey 960 board, setting the jumpers on the board, building and flashing the l-loader, firmware package, partition tables, UEFI loader, ARM Trusted Firmware, and optional Op-TEE. Links for the normal Linux kernel configuration, multi-interface bridge configuration, and single interface IPSec configuration are below. Additional kernel config modifications may be needed for certain types of applications.

kernel build instructions

mkdir /usr/local/toolchains
cd /usr/local/toolchains/
wget https://releases.linaro.org/components/toolchain/binaries/latest/aarch64-linux-gnu/gcc-linaro-7.2.1-2017.11-x86_64_aarch64-linux-gnu.tar.xz
tar -xJf gcc-linaro-7.2.1-2017.11-x86_64_aarch64-linux-gnu.tar.xz
export ARCH=arm64
export CROSS_COMPILE=/usr/local/toolchains/gcc-linaro-7.2.1-2017.11-x86_64_aarch64-linux-gnu/bin/aarch64-linux-gnu-
export PATH=/usr/local/toolchains/gcc-linaro-7.2.1-2017.11-x86_64_aarch64-linux-gnu/gcc-aarch64-linux-gnu/bin:$PATH
cd /usr/local/src
git clone https://android.googlesource.com/kernel/hikey-linaro

cd hikey-linaro
git checkout -b android-hikey-linaro-4.9 

make hikey960_defconfig
make -j8

multi-interface bridge configuration 

Bridged configuration, no ip addresses on dual nic interfaces. (crossover cable is useful for testing). Bridge interface obtains dhcp address(/11) from wlan router. aliased interface added to br0 and assigned private subnet ip on different subnet (/8). Spanning tree set on bridge interface. Basic ebtables and iptables ruleset below.

brctl addbr <br>
brctl addif <br> <eth1> <eth2>
ifconfig <br> up
ifconfig <eth1> up
ifconfig <eth2> up
brctl stp <br> yes
dhclient <br>
ifconfig <br>:0 <a.b.c.d/sn> up

iptables --table nat --append POSTROUTING --out-interface <br> -j MASQUERADE
iptables -P INPUT DROP
iptables --append FORWARD --in-interface <br>:0 -j ACCEPT
ebtables -P FORWARD DROP
ebtables -P INPUT DROP
ebtables -P OUTPUT DROP
ebtables -t filter -A FORWARD -p IPv4 -j ACCEPT
ebtables -t filter -A INPUT -p IPv4 -j ACCEPT
ebtables -t filter -A OUTPUT -p IPv4 -j ACCEPT
ebtables -t filter -A INPUT -p ARP -j ACCEPT
ebtables -t filter -A OUTPUT -p ARP -j ACCEPT
ebtables -t filter -A FORWARD -p ARP -j REJECT
ebtables -t filter -A FORWARD -p IPv6 -j DROP
ebtables -t filter -A FORWARD -d Multicast -j DROP
ebtables -t filter -A FORWARD -p X25 -j DROP
ebtables -t filter -A FORWARD -p FR_ARP -j DROP
ebtables -t filter -A FORWARD -p BPQ -j DROP
ebtables -t filter -A FORWARD -p DEC -j DROP
ebtables -t filter -A FORWARD -p DNA_DL -j DROP
ebtables -t filter -A FORWARD -p DNA_RC -j DROP
ebtables -t filter -A FORWARD -p LAT -j DROP
ebtables -t filter -A FORWARD -p DIAG -j DROP
ebtables -t filter -A FORWARD -p CUST -j DROP
ebtables -t filter -A FORWARD -p SCA -j DROP
ebtables -t filter -A FORWARD -p TEB -j DROP
ebtables -t filter -A FORWARD -p RAW_FR -j DROP
ebtables -t filter -A FORWARD -p AARP -j DROP
ebtables -t filter -A FORWARD -p ATALK -j DROP
ebtables -t filter -A FORWARD -p 802_1Q -j DROP
ebtables -t filter -A FORWARD -p IPX -j DROP
ebtables -t filter -A FORWARD -p NetBEUI -j DROP
ebtables -t filter -A FORWARD -p PPP -j DROP
ebtables -t filter -A FORWARD -p ATMMPOA -j DROP
ebtables -t filter -A FORWARD -p PPP_DISC -j DROP
ebtables -t filter -A FORWARD -p PPP_SES -j DROP
ebtables -t filter -A FORWARD -p ATMFATE -j DROP
ebtables -t filter -A FORWARD -p LOOP -j DROP
ebtables -t filter -A FORWARD --log-level info --log-ip --log-prefix FFWLOG
ebtables -t filter -A OUTPUT --log-level info --log-ip --log-arp --log-prefix OFWLOG -j DROP
ebtables -t filter -A INPUT --log-level info --log-ip --log-prefix IFWLOG

single-interface ipsec gateway configuration

iptables -t nat -A POSTROUTING -s <clientip>/32 -o <eth> -j SNAT --to-source <virtualip>
iptables -t nat -A POSTROUTING -s <clientip>/32 -o <eth> -m policy --dir out --pol ipsec -j ACCEPT

a Hardware Design for XOR gates using sequential logic in VHDL

ModelSim Full Window view with wave form output of xor simulation. ModelSim-Intel FPGA Starter Edition © Intel


XOR logic gates are a fundamental component in cryptography, and many of the typical stream and block ciphers use XOR gates. A few of these ciphers are ChaCha (stream cipher), AES (block cipher), and RSA (block cipher).

While many compiled and interpreted languages support bitwise operations such as XOR, the software implementation of both block and stream ciphers is computationally inefficient compared to FPGA and ASIC implementations.

Hybrid FPGA boards integrate FPGAs with multicore ARM and Intel application processors over high-speed buses. The ARM and Intel processors are general-purpose processors. On a hybrid board, the ARM or Intel processor is termed the hard processor system or HPS. Writing to the FPGA from the HPS is typically performed via C from an embedded Linux build (yocto or buildroot) running on the ARM or Intel core. A simple bitstream can also be loaded into the FPGA fabric without using any ARM design blocks or functionality in the ARM core for a hybrid ARM configuration.

The following is a simple hardware design written in VHDL and simulated in ModelSim. The image contains the waveform output of a simulation in ModelSim. The HPS is not used. On boot, the bitstream is loaded into the FPGA fabric. VHDL components are utilized, and a testbench is defined for testing the design. The entity and architecture VHDL design units are below.

- --three input xnor gate entity declaration - external interface to design entity
entity xnorgate is
port (
    a,b,c : in std_logic;
    q : out std_logic);
end xnorgate;

architecture xng of xnorgate is
begin
    q <= a xnor b xnor c;
end xng;

- --chain of xor / xnor gates using components and sequential logic
entity xorchain is
port (
    A,B,C,D,E,F : in std_logic;
    Av,Bv       : in std_logic_vector(31 downto 0);
    CLOCK_50    : in std_logic;
    Q           : out std_logic;
    Qv          : out std_logic_vector(31 downto 0));
end xorchain;

architecture rtl of xorchain is
component xorgate is
port (
    a,b  : in std_logic;
    q    : out std_logic);
end component;

component xnorgate is
port (
    a,b,c  : in std_logic;
    q      : out std_logic);
end component;

component xorsgate is
port (
    av : in std_logic_vector(31 downto 0);
    bv : in std_logic_vector(31 downto 0);
    qv : out std_logic_vector(31 downto 0));
end component;

signal a_in, b_in, c_in, d_in, e_in, f_in : std_logic;
signal av_in, bv_in : std_logic_vector(31 downto 0); 

signal conn1, conn2, conn3 : std_logic;

begin
    xorgt1  : xorgate port map(a => a_in, b => b_in, q => conn1); 
    xorgt2  : xorgate port map(a => c_in, b => d_in, q => conn2);
    xorgt3  : xorgate port map(a => e_in, b => f_in, q => conn3); 
    xnorgt1 : xnorgate port map(conn1, conn2, conn3, Q);
    xorsgt1 : xorsgate port map(av => av_in, bv => bv_in, qv => Qv);

   process(CLOCK_50)
   begin
       if rising_edge(CLOCK_50) then --assign inputs on rising clock edge
           a_in <= A;
           b_in <= B;
           c_in <= C;
           d_in <= D;
           e_in <= E;
           f_in <= F;
           av_in(31 downto 0) <= Av(31 downto 0);
           bv_in(31 downto 0) <= Bv(31 downto 0);
       end if;

    end process;
end rtl;

entity xorchain_tb is
end xorchain_tb;

architecture xorchain_tb_arch of xorchain_tb is
    signal A_in,B_in,C_in,D_in,E_in,F_in : std_logic := '0';
    signal Av_in                         : std_logic_vector(31 downto 0);
    signal Bv_in                         : std_logic_vector(31 downto 0);
    signal CLOCK_50_in                   : std_logic;
    signal BRK                           : boolean := FALSE;
    signal Q_out                         : std_logic;
    signal Qv_out                        : std_logic_vector(31 downto 0);

component xorchain
port (
    A,B,C,D,E,F      : in std_logic;
    Av               : in std_logic_vector(31 downto 0);
    Bv               : in std_logic_vector(31 downto 0);
    CLOCK_50         : in std_logic;
    Q                : out std_logic;
    Qv               : out std_logic_vector(31 downto 0));
end component;

begin
    xorchain_instance: xorchain port map (A => A_in,B => B_in, C => C_in, 
                                          D => D_in, E => E_in, F => F_in, Av => Av_in,
                                          Bv => Bv_in, CLOCK_50 => CLOCK_50_in, Q => Q_out,
                                          Qv => Qv_out);
clockprocess: process
    begin
        while not BRK loop
            CLOCK_50_in <= '0';
                wait for 20 ns;
                CLOCK_50_in <= '1';
                wait for 20 ns;
        end loop;
    wait;
end process clockprocess;
  
testprocess : process
    begin
        A_in <= '1';
        B_in <= '0';
        C_in <= '1';
        D_in <= '0';
        E_in <= '1';
        F_in <= '1';
        wait for 40 ns;
        A_in <= '1';
        B_in <= '0';
        C_in <= '1';
        D_in <= '0';
        E_in <= '1';
        F_in <= '0';
        wait for 20 ns;
        A_in <= '0';
        B_in <= '0';
        C_in <= '1';
        D_in <= '0';
        E_in <= '1';
        F_in <= '0';
        wait for 40 ns;
        BRK <= TRUE;
        wait;
    end process testprocess;
end xorchain_tb_arch;

entity xorgate is
port (
    a,b : in std_logic;
    q   : out std_logic);
end xorgate;

architecture xg of xorgate is
begin
    q <= a xor b;
end xg;

entity xorsgate is
port (
    av : in std_logic_vector(31 downto 0);
    bv : in std_logic_vector(31 downto 0);
    qv : out std_logic_vector(31 downto 0));
end xorsgate;

architecture xsg of xorsgate is
begin
    qv <= av xor bv;
end xsg;

Implementing Software-defined radio and Infrared Time-lapse Imaging with Tensorflow on a custom Linux distribution for the Raspberry Pi 3

GNURadio Companion Qt Gui Frequency Sync - multiple FIR filter taps
sample running on Raspberry Pi 3 custom Linux distribution

The Raspberry Pi 3 is powered by the ARM Cortex-A53 processor. This 1.2GHz 64-bit quad-core processor fully supports the ARMv8-A architecture. For this project, a custom Linux distribution was created for the Raspberry Pi 3.  

The custom Linux distribution includes support for GNURadio, several FPGA and ARM Powered SDR devices, D-STAR (hotspot, repeater, and dongle support), hsuart, libusb, hardware real-time clock support, Sony 14 megapixel NoIR image sensor, HDMI and 3.5mm audio, USB Microphone input, X-windows with Xfce, Lighttpd and PHP, Bluetooth, WiFi, SSH, TCPDump, Docker, Docker registry, MySQL, Perl, Python, QT, GTK, IPTables, x11vnc, SELinux, and full native-toolchain development support.

The Sony 14 megapixel image sensor with the infrared filter removed can be connected to the Raspberry Pi 3's MIPI camera serial interface. Image capture and recognition can then be performed over contiguous periods of time, and time-lapsed video can be created from the images. With support for Tensorflow and OpenCV, object recognition within images can be performed.

D-STAR hotspot with time-lapsed infrared imaging.

For the initial run, an infrared Time-lapse Video was created from an initial image capture run of one 3280x2460 infrared jpeg image captured every 15 seconds for three hours. 40, 5mm, 940nm LEDs, powered by 500ma over 12v DC, provided infrared illumination in the 940nm wavelength.

Tensorflow ran in the background (on v4l2 kmod) and provided continuous object recognition and scoring within each image via a sample model. Finally, OpenCV was also installed in the root file system.

The time-lapse infrared video was captured of the living room using the above setup. Below this image are images of Tensorflow running in a terminal in the background on the Raspberry Pi 3 and recognizing/scoring objects in the living room.

Tensorflow running on the Raspberry Pi 3 and continuously capturing frames from the image sensor and scoring objects

 

GNURadio Companion running on xfce on the Raspberry Pi 3

Profiling Multiprocess C programs with ARM DS-5 Streamline

The ARM DS-5 Streamline Performance Analyzer is a powerful tool for debugging, profiling, and analyzing multithreaded and multiprocess C programs.  Instructions can easily be traced between load and store operations.  Per process and per thread function call paths can be broken down by system utilization percentage.  Branch mispredictions and multi-level CPU caches can be analyzed. Furthermore, disk I/O usage, stack and heap usage, and a number of other useful metrics can quickly be referenced within the debugger. These are just a few of its capabilities.

In order to capture meaningful information from the DS-5 Streamline Performance Analyzer tool, a Linux, multiprocess, C program was modified to insert 1000 packets into a packet processing simulation buffer.  A code excerpt from the program is below.  The child processes were modified to sleep and then wake 1000 times in order to simulate process activity.  The program was analyzed using the DS-5 Streamline Performance Analyzer tool.  There are two screenshots below the code excerpt where the program is loaded into the DS-5 Streamline Performance Analyzer.

void *insertpackets(void *arg) {
   
   struct pktbuf *pkbuf;
   struct packet *pkt;
   int idx;

   if(arg != NULL) {
   
      pkbuf = (struct pktbuf *)arg;

      /* seed random number generator */
      ...

      /* insert 1000 packets into the packet buffer */
      for(idx = 0; idx < 1000; ++idx) {

         pkt = (struct packet *)malloc(sizeof(struct packet));

         if(pkt != NULL) {

            /* set the packet processing simulation multiplier to 3 */
            pkt->mlt=...()%3;

            /* insert packet in the packet buffer */
            if(pkt_queue(pkbuf,pkt) != 0) {
            
               ...
            ... 
         ...
      ...
   ...
...

int fcnb(time_t secs, long nsecs) {
 
   struct timespec rqtp;
   struct timespec rmtp;
   int ret;
   int idx;

   rqtp.tv_sec = secs;
   rqtp.tv_nsec = nsecs; 

   for(idx = 0; idx < 1000; idx++) {

      ret = nanosleep(&rqtp, &rmtp);

      ...
   ...
... 

ARM DS-5 Streamline - Profiling the process creation application

ARM DS-5 Streamline - Code View with C code in the top window
and ARM assembly instructions in the bottom window

https://github.com/brhinton/de0-nano-soc/blob/main/run.c

VHDL Processes for Pulsing Multiple GPIO Pins at Different Frequencies on Altera FPGA

 

DE1-SoC GPIO Pins connected to 780nm Infrared Laser Diodes, 660nm Red Laser Diodes, and Oscilloscope

The following VHDL processes pulse the GPIO pins at different frequencies on the Altera DE1-SoC using multiple Phase-Locked Loops. Several diodes were connected to the GPIO banks and pulsed at a 50% duty cycle with 16mA across 3.3V. Each GPIO bank on the DE1-SoC has 36 pins. Pin 1 is pulsed at 20Hz from GPIO bank 0, and pins 0 and 1 are pulsed at 30Hz from GPIO bank 1. A direct mode PLL with locked output was configured using the Altera Quartus Prime MegaWizard. The PLL reference clock frequency is set to 50MHz, the output clock frequency is set to 50MHz, and the duty cycle is set to 50%. The pin mappings for GPIO banks 0 and 1 are documented on the DE1-SoC datasheet.

Pulsed Laser Diodes via GPIO pins on DE1-SoC FPGA

- -- ---------------------
- -- CLOCK A AND B PROCESSES --
- -- INPUT: direct mode pll with locked output 
- -- and reference clock frequency set to 50MHz, 
- -- output clock frequency set to 50MHz with 50% duty 
- -- cycle and output frequency scaled by freq divider constant
- -- ----------------------------------------------------------- 

clk_a_process : process (lkd_pll_clk_a)
begin
    if rising_edge(lkd_pll_clk_a) then
        if (cycle_ctr_a < FREQ_A_DIVIDER) then
            cycle_ctr_a <= cycle_ctr_a + 1;
        else
            cycle_ctr_a <= 0;
        end if;
    end if;
end process clk_a_process;
 
clk_b_process : process (lkd_pll_clk_b)
begin
    if rising_edge(lkd_pll_clk_b) then
        if (cycle_ctr_b < FREQ_B_DIVIDER) then
            cycle_ctr_b <= cycle_ctr_b + 1;
        else
            cycle_ctr_b <= 0;
        end if;
    end if;
end process clk_b_process; 

- -- ---------------------
- -- GPIO A AND B PROCESSES --
- -- INPUT: direct mode pll with locked output
- -- ------------------------------------------------------- 
gpio_a_process : process (lkd_pll_clk_a)
begin
    if rising_edge(lkd_pll_clk_a) then
        if (cycle_ctr_a = 0) then
            gpio_sig_0 <= NOT gpio_sig_0;
        end if;
    end if;
end process gpio_a_process;

gpio_b_process : process (lkd_pll_clk_b)
begin
    if rising_edge(lkd_pll_clk_b) then
        if (cycle_ctr_b = 0) then
            gpio_sig_1 <= NOT gpio_sig_1;
        end if;
    end if;
end process gpio_b_process;
GPIO_0 <= gpio_sig_0;
GPIO_1 <= gpio_sig_1;

FPGA Audio Processing with the Cyclone V Dual-Core ARM Cortex-A9

The DE1-SoC FPGA Development board from Terasic is powered by an integrated Altera Cyclone V FPGA and ARM MPCore Cortex-A9 processor. The FPGA and ARM core are connected by a high-speed interconnect fabric. Linux can be booted on the ARM core and the FPGA and ARM core can communicate.

The DE1-SoC board below has been programmed via Quartus Prime running on Fedora 23, 64-bit Linux. The FPGA bitstream was compiled from the Terasic Audio codec design reference. After the bitstream was loaded on to the FPGA over the USB blaster II interface, the NIOS II command shell was used to load the NIOS II software image onto the chip. A menu-driven, debug interface is running from a terminal on the host via the NIOS II shell with the target connected over the USB Blaster II interface.

A low-level hardware abstraction layer was programmed in C to configure the on-board audio codec chip. The NIOS II chip is stored in on-chip memory and a PLL driven, clock signal is fed into the audio chip. The Verilog code for the hardware design was generated from Qsys. The design supports configurable sample rates, mic in, and line in/out.

Additional components are connected to the DE1-SoC board in this photo. The Linear DC934A (LTC2607) DAC is connected to the DE1-SoC and an oscilloscope is connected to the ground and vref pins on the DAC.

The DC934A features an LTC2607 16-Bit Dual DAC with i2c interface and an LTC2422 2-Channel 20-Bit uPower No Latency Delta Sigma ADC.

3.5mm audio cables are connected to the mic in and line out ports, respectively. The DE1-SoC is connected to an external display over VGA so that a local console can be managed via a connected keyboard and mouse when Linux is booted from uSD.

With GPIO pins accessible via the GPIO 0 and 1 breakouts, external LEDs can be pulsed directly from the Hard Processor System (HPS), FPGA, or the FPGA via the HPS.

Configuring the Altera Cyclone V FPGA SoC Boot loader on a DE0-Nano-SoC board

Understanding the boot loader on a computer system is probably the most important aspect of security. Most computer systems have multiple boot loaders that run in sequence immediately after a power reset is applied to the processor on the computer system.  This applies to embedded, desktop, and server systems.

The Altera Cyclone V SoC has an FPGA and a Hard Processor System (HPS) woven into a single processor package.  The HPS is a dual core ARM Cortex A9.  Building everything from scratch is the best way to figure out how the system works.

The boot sequence on a Cyclone V HPS works like this:

The On-chip ROM (for which source code is not provided) loads the preloader (1st stage bootloader). The preloader then loads U-boot. U-boot then loads the kernel and root file system.

There are two well thought out options for the preloader according to the Cyclone V boot guide.  The two options are licensed differently depending on how the source code is built. One is licensed under a BSD license and the other under GPL v2 with U-Boot.

Building a pre-loader image for the DE0-Nano-SoC board was straightforward.  Altera provides the bsp-editor utility for customizing the preloader configuration and generating the BSP HPS preloader source code, after which, make is used to build the sources using the Mentor ARM cross toolchain.
The preloader settings directory can be found on the DE0-Nano-SoC CD in the DE0_NANO_SOC_GHRD subdirectory.

The preloader load address can be set via the bsp-editor so that the on chip ROM either loads the preloader from an absolute zero address on the sdcard or from a fat partition with id equal to a2 on the sdcard.  These are the options for booting from the sdcard.

After the sources are generated and the preloader image is built using the Makefile, U-boot must be compiled. An Altera port of U-Boot is available on github for the Cyclone V FPGA SoC. U-Boot is built using the Linaro ARM cross toolchain.

There's quite a bit that can be done with the Cyclone V FPGA SoC boot configuration.  FPGA images can be loaded from U-boot.  The jumpers on the board can be configured to boot from the on-board serial flash (QSPI), bare metal applications can be loaded from the preloader, the FPGA can be configured from serial flash, and the list goes on.  The HPS SoC Boot Guide for the Cyclone V SoC  is a valuable reference and contains all of the boot configuration information.

The "Three Fives" Discrete 555 Timer Kit

The NE555 timer IC is a classic and widely used component in electronic circuits, so building a transistor-scale replica of it is a great way to understand how it works at a fundamental level. It's also a good way to develop your soldering skills and learn how to use an oscilloscope to measure signals in a circuit.

I picked up a "Three Fives" Discrete Timer Kit this weekend. As it turns out the kit was well worth the money. The "Three Fives" Discrete Timer Kit is a transistor-scale replica of the NE555 timer IC. The printed circuit board (PCB) is high-quality and soldering the transistors and resistors was alot of fun. Thanks to Eric Schlaepfer and Evil Mad Scientist Labs for this high quality circuit kit.

The size of the board makes it easy to measure what's going on inside the circuit. Just connect the probes from an oscilloscope to any of the solder or test points on the board.

A photo of the board that I built is below. I also wired a sample test circuit for blinking a pink LED and then connected a scope to the board so that I could look at the square wave.

 

Creating a custom Linux BSP for an ARM Cortex-A9 SBC with Yocto 1.8 - Part III

In part III of this guide, the installation of the final image to the SD card will be covered.  The SD card will then be booted on the target.  Finally, audio recording and playback will be tested.

Part III of this guide consists of the following sections.

1. Write the GNU/Linux BSP image to an SD card.
2. Set the physical switches on the RioTboard (Internet of Things) to boot from the uSD or SD card.
3. Connect the target to the necessary peripherals for boot.
4. Test audio recording, audio playback, and Internet connectivity.

1.  Write the GNU/Linux BSP image to an SD card

At this point, the build should be complete, without errors.  The output should be as follows.

 real 254m28.335s
 user 737m9.307s
 sys 133m39.529s

Insert an SD card into an SD card reader, connect it to the host, and execute the following commands on the host.

 host]$ cd $HOME/src/fsl-community-bsp/build /tmp/deploy/images/imx6dl-riotboard
 host]$ sudo umount /dev/sd<X>
 host]$ sudo dd if=bsec-image-imx6dl-riotboard.sdcard of=/dev/sd<X> bs=1M
 host]$ sudo sync

2. Set the physical switches on the RioTboard to boot from the uSD or SD card.

For booting from the SD card on the bottom of the target, set the physical switches as follows.

SD (J6, bottom) 1 0 1 0 0 1 0 1

For booting from the uSD card on the top of the target, set the physical switches as follows.

uSD (J7, top) 1 0 1 0 0 1 1 0

3. Connect the target to the necessary peripherals for boot.

There are two options

Option 1

Connect one end of an ethernet cable to the target. Connect the other end of the ethernet cable to a hub or DHCP server.  

Connect the board to the host computer via the J18 serial UART pins on the target.  This will require a serial to USB breakout cable.  Connect TX, RX, and GND to RX, TX, and GND on the cable. The cable must have an FTDI or similar level shifter chip. Connect the USB end of the cable to the host computer.

Connect the speakers to the light green 3.5 mm audio out jack and the microphone to the pink 3.5 mm MIC In jack.

Connect a 5V / 4 AMP DC power source to the target.

Run minicom on the host computer. Configure minicom at 115200 8N1 with no hardware flow control and no software flow control. If a USB to serial cable with an FTDI chip in it is used, then the cable should show up in /dev as ttyUSB0 in which case, set the serial device in minicom to /dev/ttyUSB0.

If this option was chosen, drop into U-boot after power on by pressing Enter on the host keyboard with minicom open and connected.

If enter is not pressed after power-on, the target will boot and a login prompt will appear.

A login prompt will not appear.

Option 2

Connect one end of an ethernet cable to the target. Connect the other end of the ethernet cable to a hub or DHCP server.  

Connect a USB keyboard, USB mouse, and monitor (via an HDMI cable) to the target.

Connect the speakers to the light green 3.5 mm audio out jack and the microphone to the pink 3.5 mm MIC In jack.

Connect a 5V / 4 AMP DC power source to the target.

A login prompt will now appear.

4. Test audio recording, audio playback, and Internet connectivity

Type root to log in to the target. The root password is not set.

Execute the following commands on the target

 root@imx6dl-riotboard: alsamixer 

Press F6.
Press arrow down so that 0 imx6-riotboard-sgtl5000 is highlighted.
Press Enter.
Increase Headphone level to 79<>79.
Increase PCM level to 75<>75.
Press Tab.
Increase Mic level to 59.
Increase Capture to 80<>80.
Press Esc.

 root@imx6dl-riotboard: cd /usr/share/alsa/sounds
 root@imx6dl-riotboard: aplay *.wav 

A sound should be played through the speakers.

 root@imx6dl-riotboard: cd /tmp
 root@imx6dl-riotboard: arecord -d 10 micintest.wav

Talk into the microphone for ten seconds.

 root@imx6dl-riotboard: aplay micintest.wav

A recording should play through the speakers.

 root@imx6dl-riotboard: ping riotboard.org

An ICMP reply should be received.

Creating a custom Linux BSP for an ARM Cortex-A9 SBC with Yocto 1.8 - Part II

In the second part of this guide, the source code will be pulled, the build configuration will be customized, and the build will be executed.  Part II of this guide consists of the following sections.

1. Pull the Freescale community BSP platform source code from github. 
2. Setup the build environment using the predefined imx6dl-riotboard RioTboard (Internet of Things) machine.
3. Create a new layer for the custom Linux distribution.
4. Customize the image in the meta-bsec layer. 
5. Create layer.conf file in the meta-bsec layer. 
6. Create the distribution configuration file in the meta-bsec layer. 
7. Add the new layer to bblayers.conf.
8. Customize the local configuration.
9. Execute
   the build.

1. Pull the Freescale community BSP platform source code from github.

Execute the following commands on the host.

 host]$ mkdir $HOME/bin  
 host]$ curl https://storage.googleapis.com/git-repo-downloads/repo > ~/bin/repo 
 host]$ chmod a+x $HOME/bin/repo  
 host]$ echo "PATH=$PATH:$HOME/bin" >> $HOME/.bashrc  
 host]$ source .bashrc  
 host]$ mkdir -p $HOME/src/fsl-community-bsp  
 host]$ cd $HOME/src/fsl-community-bsp  
 host]$ repo init -u https://github.com/Freescale/fsl-community-bsp-platform -b fido  
 host]$ repo sync  

2. Setup the build environment using the predefined imx6dl-riotboard machine.

Execute the following commands on the host.

 host]$ MACHINE=imx6dl-riotboard . ./setup-environment build  

3. Create a new layer for the custom Linux distribution

Execute the following commands on the host.

 host]$ cd $HOME/src/fsl-community-bsp/sources  
 host]$ mkdir -p meta-bsec/conf/distro  
 host]$ mkdir -p meta-bsec/recipes-bsec/images  
 host]$ cd poky/meta/recipes-extended/images  
 host]$ cp core-image-full-cmdline.bb \
        ../../../../meta-bsec/recipes-bsec/images/bsec-image.bb

4. Customize the image in the meta-bsec layer.

Execute the following commands on the host.

  host]$ cd $HOME/src/fsl-community-bsp/sources/meta-bsec/recipes-bsec/images

Customize bsec-image.bb as follows.  Lines with bold text indicate lines to add to the file.

 DESCRIPTION = "A console-only image with more full-featured Linux system \
 functionality installed."

 # customize IMAGE_FEATURES as follows
 IMAGE_FEATURES += "dev-pkgs tools-sdk tools-debug tools-profile tools-testapps \
 debug-tweaks splash ssh-server-openssh package-management"

 # packagegroup-core-tools-profile will build and install tracing and profiling tools to the target image.
 # packagegroup-core-buildessential will build and install autotools, gcc, etc. to the target image.
 # kernel-modules for install of the kernel modules.
 # kernel-devsrc for building out of tree modules.
 # IMAGE_ROOTFS_EXTRA_SPACE_append for adding extra space to the target rootfs image.

 # customize IMAGE_INSTALL as follows
 IMAGE_INSTALL = "\
     packagegroup-core-boot \
     packagegroup-core-full-cmdline \
     packagegroup-core-tools-profile \
     packagegroup-core-buildessential \
     kernel-modules \
     ${CORE_IMAGE_EXTRA_INSTALL} \
     kernel-devsrc \
     "
 inherit core-image
 
 # Add extra space to the rootfs image
 IMAGE_ROOTFS_EXTRA_SPACE_append += "+ 3000000"

5. Create layer.conf file in the meta-bsec layer.

Create sources/meta-bsec/conf/layer.conf with the below contents.

BBPATH .= ":${LAYERDIR}"  
 BBFILES += "${LAYERDIR}/recipes-*/*/*.bb \  
     ${LAYERDIR}/recipes-*/*/*.bbappend"  
 BBFILE_COLLECTIONS += "bsec"  
 BBFILE_PATTERN_bsec = "^${LAYERDIR}/"  
 BBFILE_PRIORITY_bsec = "6"  

6. Create the distribution configuration file in the meta-bsec layer.

Create sources/meta-bsec/conf/disro/bsecdist.conf with the below contents.

 require conf/distro/poky.conf    
 # distro name
 DISTRO = "bsecdist"    
 DISTRO_NAME = "bsecdist distribution"    
 DISTRO_VERSION = "1.0"    
 DISTRO_CODENAME = "bsc"    
 DISTRO_FEATURES_append = " alsa usbhost usbgadget keyboard bluetooth"
 SDK_VENDOR = "-bsecdistsdk"    
 SDK_VERSION := "${@'${DISTRO_VERSION}'.replace('snapshot-${DATE}','snapshot')}"    
 MAINTAINER = "bsecdist "    
 INHERIT += "buildhistory"    
 BUILDHISTORY_COMMIT = "1"

7. Add the new layer to bblayers.conf

Execute the following commands on the host.

 host]$ cd $HOME/src/fsl-community-bsp/build/conf

Customize bblayers.conf by adding the meta-bsec layer to BBLAYERS as follows.

 LCONF_VERSION = "6"

 BBPATH = "${TOPDIR}"
 BSPDIR := "${@os.path.abspath(os.path.dirname(d.getVar('FILE', True)) + '/../..')}"

 BBFILES ?= ""
 BBLAYERS = " \
   ${BSPDIR}/sources/poky/meta \
   ${BSPDIR}/sources/poky/meta-yocto \
   \
   ${BSPDIR}/sources/meta-openembedded/meta-oe \
   ${BSPDIR}/sources/meta-openembedded/meta-multimedia \
   \
   ${BSPDIR}/sources/meta-fsl-arm \
   ${BSPDIR}/sources/meta-fsl-arm-extra \
   ${BSPDIR}/sources/meta-fsl-demos \
   ${BSPDIR}/sources/meta-bsec \
 "

8. Customize the local configuration

Customize local.conf as follows.

 MACHINE ??= 'imx6dl-riotboard'
 # set distro name
 DISTRO ?= 'bsecdist'
 PACKAGE_CLASSES ?= "package_rpm package_deb"
 EXTRA_IMAGE_FEATURES = " "
 USER_CLASSES ?= "buildstats image-mklibs image-prelink"
 PATCHRESOLVE = "noop"
 BB_DISKMON_DIRS = "\
      STOPTASKS,${TMPDIR},1G,100K \
      STOPTASKS,${DL_DIR},1G,100K \
      STOPTASKS,${SSTATE_DIR},1G,100K \
      ABORT,${TMPDIR},100M,1K \
      ABORT,${DL_DIR},100M,1K \
      ABORT,${SSTATE_DIR},100M,1K" 
 PACKAGECONFIG_append_pn-qemu-native = " sdl"
 PACKAGECONFIG_append_pn-nativesdk-qemu = " sdl"
 ASSUME_PROVIDED += "libsdl-native"
 CONF_VERSION = "1"
 BB_NUMBER_THREADS = '4'
 PARALLEL_MAKE = '-j 4'
 DL_DIR ?= "${BSPDIR}/downloads/"
 ACCEPT_FSL_EULA = "1"
 # archive source code for all of the packages that will be built into the image
 INHERIT += "archiver"
 ARCHIVER_MODE[src] = "original"
 # ensure that license files accompany each binary in final image
 COPY_LIC_MANIFEST = "1"
 COPY_LIC_DIRS = "1"
 # setup source mirror
 # make sure that bitbake checks for all of the source tarballs in a local directory 
 # before going to the Internet to fetch them.
 SOURCE_MIRROR_URL ?= "file://${BSPDIR}/source-mirror/"
 INHERIT += "own-mirrors"
 # create a shareable cache of source code management backends
 BB_GENERATE_MIRROR_TARBALLS = "1"

9. Execute the build

Execute the following commands on the host.

 host]$ cd $HOME/src/fsl-community-bsp/build 
 host]$ time bitbake bsec-image 

While the image is building, please take note of the following.

The input specifications for the GNU/Linux kernel and U-boot segments of the BSP are in the below files. These specifications include such things as GNU/Linux kernel patch files for i.MX 6 processor features, kernel boot args, kernel load address, cortex specific tuning parameters, etc.

 sources/meta-fsl-arm-extra/conf/machine/imx6dl-riotboard.conf  
 sources/poky/meta-yocto/conf/distro/poky.conf  
 sources/meta-fsl-arm/recipes-kernel/linux/linux-imx.inc  
 sources/meta-fsl-arm/recipes-kernel/linux/linux-fslc_4_0.bb  
 sources/poky/meta/conf/machine/include/tune-cortexa9.inc

In part III of this guide, the image will be booted on the target and then audio will be tested, including recording and playback. Continue to part III of this guide.

Continue to Part III

Creating a custom Linux BSP for an ARM Cortex-A9 SBC with Yocto 1.8 - Part I

This guide is an update to "Creating a custom Linux distribution for an ARM® Cortex®-A9 based SBC" and provides directions for building a GNU/Linux BSP for the RioTboard (Internet of Things) with Yocto 1.8 on a 64-bit Fedora 21 GNU/Linux host.  The latest stable version of Yocto 1.8 has been incorporated along with build instructions for version 4.0.7 of the GNU/Linux kernel with i.MX 6 patches, U-boot, audio recording and playback support, and a full kernel and application development environment on the target.

This guide is split into three parts as follows.

I. Creating a custom Linux BSP for the RioTboard (Internet of Things) with Yocto 1.8- Part I

1. Hardware and software prerequisites.
2. Required Packages for a 64-bit Fedora 21 Host development system.

II. Creating a custom Linux BSP for the RioTboard with Yocto 1.8 - Part II

1. Pull the Freescale community BSP platform source code from github. 
2. Setup the build environment using the predefined imx6dl-riotboard machine.
3. Create a new layer for the custom Linux distribution.
4. Customize the image in the meta-bsec layer. 
5. Create layer.conf file in the meta-bsec layer. 
6. Create the distribution configuration file in the meta-bsec layer. 
7. Add the new layer to bblayers.conf.
8. Customize the local configuration.
9. Execute the build.

III. Creating a custom Linux BSP for the RioTboard with Yocto 1.8 - Part III

1. Write the GNU/Linux BSP image to an SD card.
2. Set the physical switches on the RioTboard to boot from the uSD or SD card.
3. Connect the target to the necessary peripherals for boot.
4. Test audio recording, audio playback, and Internet connectivity.

The BSP will consist of a GNU/Linux 4.0.7 kernel, an EXT3 root filesystem, and the U-Boot bootloader.  All components will be compiled from the latest, public sources.  The GNU/Linux system will include support for audio recording and playback via the RioTboard's MIC In and Audio Out jacks. Support will be built for ethernet, ipv4, bluetooth, USB host and USB gadget, and an ssh server.  The final target image will also contain native ARM compilers, a full SDK, strace, GDB, package management tools, and the GNU/Linux 4.0.7 kernel source code with i.MX 6 patches already applied.

In the first guide for Yocto 1.7, a custom distribution and target image was created by extending the core-image-minimal image.  In this guide, a custom distribution and target image will be created by extending the core-image-full-cmdline image.  The resulting target image will be larger in size but will include a much richer set of features for kernel and application level development and debugging on the target.

Finally, Yocto will be configured so that all source packages are archived in their original format with accompanying license files.

To start with, please read Setting up an ARM® Cortex®-A9 based SBC which outlines the necessary components to get started.  A microphone and a set of powered speakers will be needed, both with 3.5mm connectors.  An Audio-Technica ATR4650 microphone and a pair of Logitech S-00134 powered speakers will be onnected to the RioTboard.  These will be needed for testing audio recording and playback.

1. Hardware and software prerequisites

Host Operating System

Fedora release 21 for x86_64
GNU/Linux kernel 4.0.7-200.fc21.x86_64 #1 SMP

Host Hardware

Intel(R) Core(TM) i7-4600U CPU @ 2.10GHz
Physical Memory 12 GB
My /home partition is 414 GB and resides on a solid state hard drive.


The Yocto build requires a large amount of space so it is recommend keeping a scratch area in the /home partition of at least 100 GB.

2. Required Packages for a 64-bit Fedora 21 Host development system

from the Yocto Project Mega Manual Revision 1.8

Execute the following commands on the host.

 host]$ sudo yum install gawk make wget tar bzip2 gzip python unzip perl patch \
        diffutils diffstat git cpp gcc gcc-c++ glibc-devel texinfo chrpath \
        ccache perl-Data-Dumper perl-Text-ParseWords perl-Thread-Queue socat \
        findutils which
 host]$ sudo yum install SDL-devel xterm perl-Thread-Queue
 host]$ sudo yum install make docbook-style-dsssl docbook-style-xsl \
        docbook-dtds docbook-utils fop libxslt dblatex xmlto xsltproc
 host]$ sudo yum install autoconf automake libtool glib2-devel

In Part II, the  source code for the kernel, boot loader, and root file system packages will be pulled.  All components will then be built from source and the GNU/Linux BSP image will be created for the target.

Continue to Part II

Customizing a Linux distribution for an ARM Cortex-A9 SBC

The Yocto 1.7.1 (Dizzy branch) from Freescale source will be used for building a BSP for the i.MX 6 RIoTboard. The final image will consist of the following components

• U-Boot version 2014.10 from the Freescale git repositories.
• Linux kernel version 3.17.4 from the Freescale git repositories.
• ext3 root filesystem with selected packages

The image will be built from the custom distribution (bsecdist) and custom image (bsec-image) defined in the last post. bsec-image is derived from core-image-minimal. The configuration changes below will add support for package tests to the baec-image. In addition, the profiling tools and static development libraries and header files will be added to the image. Finally, several standard userspace packages will be added to baec-image; namely, bison, flex, and and gunning. Last, several configuration directives will be added to the local configuration file so that source code archives, package versions, and accompanying license files are stored and cached in a local directory for future builds and compliance purposes.

1. Add profiling tools and static development packages to image

First, add the following profiling tools contained within the tools-profile package to the final image. Add static versions of the development packages to the target image. Therefore, add the IMAGE_FEATURES line to bsec-image.bb as follows.

sources/meta-bsec/recipes-bsec/images/bsec-image.bb should contain the following

SUMMARY = "A small image just capable of allowing a device to boot."
IMAGE_INSTALL = "packagegroup-core-boot ${ROOTFS_PKGMANAGE_BOOTSTRAP} ${CORE_IMAGE_EXTRA_INSTALL}"
IMAGE_LINGUAS = " "
LICENSE = "MIT"
inherit core-image
IMAGE_FEATURES += " tools-profile staticdev-pkgs"
IMAGE_ROOTFS_SIZE ?= "8192"

2. Add bison, flex, and gnupg packages to image

Now add bison, flex, and gnupg to the list of packages installed to the target image.
Add the following line to bsec-image.bb after the IMAGE_FEATURES line as follows.

sources/meta-bsec/recipes-bsec/images/bsec-image.bb should contain the following

SUMMARY = "A small image just capable of allowing a device to boot."
IMAGE_INSTALL = "packagegroup-core-boot ${ROOTFS_PKGMANAGE_BOOTSTRAP} ${CORE_IMAGE_EXTRA_INSTALL}"
IMAGE_LINGUAS = " "
LICENSE = "MIT"
inherit core-image
IMAGE_FEATURES += " tools-profile staticdev-pkgs"
CORE_IMAGE_EXTRA_INSTALL += "bison flex gnupg"
IMAGE_ROOTFS_SIZE ?= "8192"

3. List available packages

The full list of available packages can be viewed by executing the following command

$ bitbake -s

4. Setup source code archiving for all packages contained within image

Next, archive the source code for all packages contained within the image.
This can be achieved by adding the following two lines to the end of the build/conf/local.conf file

INHERIT += "archiver"
ARCHIVER_MODE[src] = "original"

5. Ensure license files are archived and included with binaries.

Subsequently, ensure that the license files accompany each binary in the final image by adding the following two lines to the end of the build/conf/local.conf file.

COPY_LIC_MANIFEST = "1"
COPY_LIC_DIRS = "1"

6. Add package testing to build

Now, add package testing to the build by adding the following two lines to bsec-image.bb

The contents of sources/meta-bsec/recipes-bsec/images/bsec-image.bb should be as follows

SUMMARY = "A small image just capable of allowing a device to boot."
IMAGE_INSTALL = "packagegroup-core-boot ${ROOTFS_PKGMANAGE_BOOTSTRAP} ${CORE_IMAGE_EXTRA_INSTALL}"
IMAGE_LINGUAS = " "
LICENSE = "MIT"
inherit core-image
IMAGE_FEATURES += " tools-profile staticdev-pkgs"
CORE_IMAGE_EXTRA_INSTALL += "bison flex gnupg"
DISTRO_FEATURES_append = " ptest"
EXTRA_IMAGE_FEATURES += "ptest-pkgs"
IMAGE_ROOTFS_SIZE ?= "8192"

7. Setup source code mirror so that package sources can be fetched from cache

Next, make sure that bitbake checks for all of the source tarballs in a local directory before going to the Internet to fetch them. This can be achieved by adding the following lines to the end of the build/conf/local.conf file.

SOURCE_MIRROR_URL ?= "file://${BSPDIR}/source-mirror/"
INHERIT += "own-mirrors"

8. Create shareable cache of git and svn backends

Finally, create a shareable cache of source code management backends by adding the following to the end of the build/conf/local.conf file.

BB_GENERATE_MIRROR_TARBALLS = “1”

After an initial build is performed, the directory contents of download/ can be recursively copied into source-mirror/ and the following line can be added to the end of the build/conf/local.conf file.

BB_NO_NETWORK = “1”

Consequently, all future builds will not fetch anything from the Internet and all package sources will be obtained from the sources in source-mirror.

9. Kick off the build

Kick off the build as follows

$ cd $HOME/src/fsl-community-bsp
$ MACHINE=imx6dl-riotboard . ./setup-environment build  
$ bitbake bsec-image

10. Copy sources to mirror

Copy the sources from the downloads directory to source-mirror by executing the following commands

$ cd ..
$ cp -R downloads/*.* source-mirror/

After the build is complete, the license file for each package will be contained within the appropriately named subdirectory of build/tmp/deploy/licenses

The image manifest file build/tmp/deploy/images/imx6dl-riotboard/bsec-image-imx6dl-riotboard.manifest will contain a list of package names and associated versions for each of the packages in the image.


11. Boot the custom distribution image

After the build is complete, write the image to an SD Card as follows

$ cd build/tmp/deploy/images/imx6dl-riotboard

$ sudo umount /dev/sdX
$ sudo dd if=bsec-image-imx6dl-riotboard.sdcard of=/dev/sdb bs=1M
$ sudo sync

Insert the SD Card in the J6 SD Card slot on the bottom of the RiOTboard, connect the board to the Host over Serial UART, run minicom at 115200,8N1 from a terminal on the Host, and power on the board.

Creating a custom Linux distribution for an ARM Cortex-A9 SBC

The Yocto project provides an ideal platform for building a custom Linux distribution.  It's design was intended to model a machine.  The Yocto project or machine should take a number of inputs and produce an output.  The inputs to the machine are the specifications for the Linux distribution.  The output of the machine is the Linux distribution.

 

The Yocto project is the most widely supported system for building custom Linux distributions.

The Yocto project is very well supported by both communities and companies.  The project consists of a tool called bitbake and a build system that is based off of OpenEmbedded.  Together, these two components along with a defined set of metadata comprise what is called the Poky reference platform.

Yocto supports numerous architectures through OpenEmbedded. These include x86, ARM®, MIPS, and PowerPC.  Yocto's most attractive feature is its support of what are called layers.  Layers allow the abstraction of individual components or sets of components within a board support package (BSP). New layers can be derived from existing layers to enhance functionality, patch source code, or remove subsets of unneeded components.  

Building support for a custom boot loader, custom kernel, custom rootfs, and development application layer is both very clean and straightforward.  SELinux has become a necessary component of almost every Linux distribution.  It is very simple to integrate SELinux into Yocto via an OpenEmbedded layer.   Consequently, building a "Carrier Grade" Linux distribution for one of the many (several hundred) processors is attainable in a short amount of time.

Embest Technology created the RIoTboard.  The board design is fairly simple.  The board contains an i.MX 6 Solo processor.  Embest Technology and Element 14 provide links to download prebuilt Linux and Android images.  Embest Technology also has a github repository where source code can be downloaded to build a complete BSP.  The complete BSP consists of the u-boot boot loader, kernel, and root filesystem.

Embest Technology took a snapshot of the Freescale Community BSP Platform source code repository at some point in the past.  The BSP source download from github, which consists of the Yocto layers for building a riotboard BSP, is not up to date with Freescale, Yocto, and OpenEmbedded.

Consequently, Freescale's community BSP platform will be used.  The platform is comprised of both the Poky reference build system and an additional series of layers which will allow us to build a custom Linux distribution for the i.MX 6 processor architecture.  

A custom Linux distribution that will be used for development should include support for only the peripheral components that will be used. The custom development distribution should be minimized to the maximum extent possible.  All I/O interfaces should be clearly documented.  Bootable media types should be documented and partition maps should be created.  These steps greatly ease development and debugging, and prevent unknown issues from cropping up after production release.  Layering in SELinux at a later time is simple.  Creating new layers for shared library development, or userspace application development is also simple and layers can be added for slicing out pieces of the kernel that aren't now, but may be needed later on.  Last but not least, blowing the appropriate fuses prior to production is critical.

To keep things simple, a new BSP or custom Linux distribution will be derived from the riotboard specifications that have already been incorporated into Freescale's community BSP platform.  

The goal here is to produce a minimal Linux distribution that can be used for development and easily extended from any level in the stack - u-boot, kernel, root filesystem, and userspace libraries or executables.  Most importantly, the architecture of this distribution will conform to the standards that have been outlined by the Yocto Project and OpenEmbedded.  This means anyone can easily pick up.

The input specifications for a generic i.MX 6 solo machine have been mostly documented in the meta-fsl-arm-extra layer.  The output image that is produced from these input specifications is an image that consists of the u-boot boot loader, i.MX 6 Solo/Dual kernel, and ext3 root filesystem.
In an effort to build a custom Linux distribution for the i.MX 6 Solo/Dual with the least amount of packages in the shortest amount of time, slimming down the input specifications, configuring the distribution, and naming it should only require modification of a few files.  Here are the steps.

First, the riotboard or target must be connected to the Fedora 20 x86_64 host via serial UART (see last blog post).  A card reader must be connected to the host via USB. 

The new distribution will be called the bsec distribution.  The bsec distribution will consist of a minimal Linux image, u-boot boot loader, and ext3 root filesystem configured for the i.MX 6 based riotboard.

Perform the following steps on the host.

1.  Pull the Freescale community BSP platform source code from github.  Dizzy is the Yocto 1.7.1 branch.   Execute the following commands on the host.

 $ mkdir $HOME/bin  
 $ curl https://storage.googleapis.com/git-repo-downloads/repo > ~/bin/repo 
 $ chmod a+x $HOME/bin/repo  
 $ echo "PATH=$PATH:$HOME/bin" >> $HOME/.bashrc  
 $ source .bashrc  
 $ mkdir -p $HOME/src/fsl-community-bsp  
 $ cd $HOME/src/fsl-community-bsp  
 $ repo init -u https://github.com/Freescale/fsl-community-bsp-platform -b dizzy  
 $ repo sync  

2.  Setup the build environment using the predefined imx6dl-riotboard machine.

 $ MACHINE=imx6dl-riotboard . ./setup-environment build  

3.  Create a new layer for the custom Linux distribution

 $ cd $HOME/src/fsl-community-bsp/sources  
 $ mkdir -p meta-bsec/conf/distro  
 $ mkdir -p meta-bsec/recipes-bsec/images  
 $ cd poky/meta/recipes-core/images  
 $ cp core-image-minimal.bb ../../../../meta-bsec/recipes-bsec/images/bsec-image.bb  

4.  Create the layer.conf file in the meta-bsec layer. 

sources/meta-bsec/conf/layer.conf should contain the following

 BBPATH .= ":${LAYERDIR}"  
 BBFILES += "${LAYERDIR}/recipes-*/*/*.bb \  
     ${LAYERDIR}/recipes-*/*/*.bbappend"  
 BBFILE_COLLECTIONS += "bsec"  
 BBFILE_PATTERN_bsec = "^${LAYERDIR}/"  
 BBFILE_PRIORITY_bsec = "6"  

5.  Create the distribution configuration file in the meta-bsec layer. 

sources/meta-bsec/conf/distro/bsecdist.conf should contain the following

 require conf/distro/poky.conf  
 DISTRO = "bsecdist"  
 DISTRO_NAME = "bsecdist distribution"  
 DISTRO_VERSION = "1.0"  
 DISTRO_CODENAME = "bsc"  
 SDK_VENDOR = "-bsecdistsdk"  
 SDK_VERSION := "${@'${DISTRO_VERSION}'.replace('snapshot-${DATE}','snapshot')}"  
 MAINTAINER = "bsecdist <e-mail-address>"  
 INHERIT += "buildhistory"  
 BUILDHISTORY_COMMIT = "1"  

6.  Added the new layer to bblayers.conf

build/conf/bblayers.conf should contain the following

 LCONF_VERSION = "6"  
 BBPATH = "${TOPDIR}"  
 BSPDIR := "${@os.path.abspath(os.path.dirname(d.getVar('FILE', True)) + '/../..')}"  
 BBFILES ?= ""  
 BBLAYERS = " \  
  ${BSPDIR}/sources/poky/meta \  
  ${BSPDIR}/sources/poky/meta-yocto \  
  \  
  ${BSPDIR}/sources/meta-openembedded/meta-oe \  
  ${BSPDIR}/sources/meta-openembedded/meta-multimedia \  
  \  
  ${BSPDIR}/sources/meta-fsl-arm \  
  ${BSPDIR}/sources/meta-fsl-arm-extra \  
  ${BSPDIR}/sources/meta-fsl-demos \  
  ${BSPDIR}/sources/poky/meta-selinux \  
  ${BSPDIR}/sources/meta-bsec \  
 "  

7.  Set the distribution to the bsec distribution in local.conf

build/conf/local.conf should contain the following

 MACHINE ??= 'imx6dl-riotboard'  
 DISTRO ?= 'bsecdist'  
 PACKAGE_CLASSES ?= "package_rpm"  
 EXTRA_IMAGE_FEATURES = "debug-tweaks"  
 USER_CLASSES ?= "buildstats image-mklibs image-prelink"  
 PATCHRESOLVE = "noop"  
 BB_DISKMON_DIRS = "\  
   STOPTASKS,${TMPDIR},1G,100K \  
   STOPTASKS,${DL_DIR},1G,100K \  
   STOPTASKS,${SSTATE_DIR},1G,100K \  
   ABORT,${TMPDIR},100M,1K \  
   ABORT,${DL_DIR},100M,1K \  
   ABORT,${SSTATE_DIR},100M,1K"  
 PACKAGECONFIG_append_pn-qemu-native = " sdl"  
 PACKAGECONFIG_append_pn-nativesdk-qemu = " sdl"  
 ASSUME_PROVIDED += "libsdl-native"  
 CONF_VERSION = "1"  
 BB_NUMBER_THREADS = '1'  
 PARALLEL_MAKE = '-j 1'  
 DL_DIR ?= "${BSPDIR}/downloads/"  
 ACCEPT_FSL_EULA = "1"  

8.  Pull the OpenEmbedded SELinux meta layer for later configuration

 $ cd sources/poky   
 $ git clone -b dizzy git://git.yoctoproject.org/meta-selinux  
 $ cd ../..  

9.  Perform the build

 $ cd build  
 $ bitbake bsec-image  

10.  Write the image to the SD card

 $ cd tmp/deploy/images/imx6dl-riotboard  
 $ sudo dd if=bsec-image-imx6dl-riotboard.sdcard of=/dev/sdX bs=1M  
 $ sudo sync  

At this point, the jumpers on the riotboard should be set to boot from the SD card.  Next, power on the riotboard with the new SD card.  If HDMI is connected,  the Das u-boot software engineering logo should appear on the display.

 bsecdist distribution 1.0 imx6dl-riotboard /dev/ttymxc1               
 imx6dl-riotboard login:  

Review the input specifications for the riotboard machine should be simple.  Start with the following files

 sources/meta-fsl-arm-extra/conf/machine/imx6dl-riotboard.conf  
 sources/poky/meta-yocto/conf/distro/poky.conf  
 sources/meta-fsl-arm/recipes-kernel/linux/linux-imx.inc  
 sources/meta-fsl-arm/recipes-kernel/linux/linux-fslc_3.17.bb  
 sources/poky/meta/conf/machine/include/tune-cortexa9.inc  

The input specifications for this image are raw and generic. They define software support for ALL of the on-board peripherals with the e-fuses left open.

Finally, the output image was 29 MB and is comprised of the u-boot boot loader, the Linux kernel, and the root file system.  This is a decent place to start before adding more software to the BSP.