rustl8710 - Rust and FreeRTOS on PADI Realtek RTL8710, updated for Visual Studio Code, OpenOCD, gdb-multiarch

Original background and usage instructions at https://polyfractal.com/post/rustl8710/

---

rustl8710 Updates

Updated article on rustl8710:
https://medium.com/@ly.lee/running-rust-and-freertos-on-the-padi-iot-stamp-fb36c5ef4844

• The rustl8710 code here has been updated to use OpenOCD instead of JLink as the JTAG tool for flashing and debugging, because JLink no longer works with the PADI SWD Debugger USB dongle. See https://forum.pine64.org/archive/index.php?thread-4579-2.html

• Replaced gdb-arm-none-eabi (obsolete) by gdb-multiarch

• Upgraded freertos.rs from version 1.0 to 2.0

• Build, flash and debug PADI from Visual Studio Code

Tested on:

• Ubuntu 18.04 LTS x86 64-bit on Oracle VirtualBox 5.2.12 (hosted on Windows 10)

• Ubuntu 18.04 LTS x86 64-bit on Intel Atom x5-Z8300 notebook PC

For Raspberry Pi, see https://github.com/lupyuen/rustl8710/blob/master/pi/README.md

---

Hardware components

You will need the following development hardware (US$ 14):

• PADI IoT Stamp with Assembled PADI Breadboard Adapter

  https://www.pine64.org/?product=assembled-padi-breadboard-adapter

• PADI SWD Debugger: For flashing and debugging the PADI

  https://www.pine64.org/?product=swd-debugger

• PADI Serial Console: For interacting with the PADI serial console input / output

  https://www.pine64.org/?product=padi-serial-console

---

Install prerequisites

1. We assume that you are running Ubuntu 18.04 LTS x86 64-bit on a PC or on Oracle VirtualBox.

2. If you're using Oracle VirtualBox, you may download the preinstalled Ubuntu image from
   https://drive.google.com/drive/folders/1Isf0lAj6otziOXYjjSrfwCW06rQEwzaG?usp=sharing

   In VirtualBox, click File → Import Appliance and select the downloaded file padi.ova.
   Start the padi virtual machine and connect with ssh to padi.local, username user, password password.

3. Run the following commands on Ubuntu:

   sudo apt update
   sudo apt install build-essential gawk bc libc6-dev:i386 lib32ncurses5-dev
   sudo apt install gcc-arm-none-eabi
   sudo apt install gdb-multiarch
   sudo apt install cutecom
   sudo apt install openocd

4. gcc-arm-none-eabi is GNU C ARM32 cross-compiler that we shall use to generate code for the ARM 32-bit architecture (used by PADI)

5. gdb-multiarch is the GNU cross-platform debugger that we shall use to debug the Rust and C code running on the PADI

6. cutecom is a simple terminal emulator that connects to the PADI serial interface for console input/output

7. openocd is the Open On-Chip Debugger that connects to the PADI SWD Debugger for flashing and debugging

Download rustl8710 code

1. Run the following command on Ubuntu:

   git clone https://github.com/lupyuen/rustl8710

2. The following software modules are included:

   • Realtek Ameba RTL8710AF SDK (from the official PADI downloads): Provides the tools to build, flash and debug PADI programs written in C, excluding the SDK docs
     https://github.com/lupyuen/rustl8710/tree/master/component
     https://github.com/lupyuen/rustl8710/tree/master/src/c

   • FreeRTOS (included in the Realtek Ameba RTL8710AF SDK)
     https://github.com/lupyuen/rustl8710/tree/master/component/os/freertos

   • Rust system and sample code
     https://github.com/lupyuen/rustl8710/tree/master/src/rust

   • freertos.rs: Rust wrapper for FreeRTOS
     https://github.com/lupyuen/rustl8710/blob/master/src/rust/Cargo.toml

3. The log folder contains sample build, flash and debug logs, for your troubleshooting convenience
   https://github.com/lupyuen/rustl8710/tree/master/log

Install Rust components

1. On Ubuntu, install rustup from https://rustup.rs/ (select default installation):

   curl https://sh.rustup.rs -sSf | sh

2. Run the following commands on Ubuntu:

   source $HOME/.cargo/env
   cd rustl8710
   rustup update
   rustup override set nightly
   rustup component add rust-src
   cargo install xargo

3. This installs the Rust compiler and libraries, as well as Xargo the Rust cross-compiler. The nightly Rust library build is selected (instead of the stable or beta builds) because Xargo requires it.

---

Select OpenOCD instead of JLink as JTAG tool

1. Run the following command on Ubuntu:

   make clean
   make setup GDB_SERVER=openocd

2. This tells the Realtek Ameba RTL8710AF SDK to use OpenOCD (instead of JLink) to connect to the PADI SWD Debugger during flash and debug operations

3. This also erases any previous build of the PADI image, e.g. from the downloaded VirtualBox virtual machine

---

Connect PADI and SWD Debugger to computer

1. Connect the PADI to your computer via the PADI SWD Debugger USB adapter according to
   http://files.pine64.org/doc/PADI/documentation/padi-jtag-swd-connections-diagram.pdf

   PADI IoT Stamp		PADI SWD Debugger
   +3.3V	[Red]	3V3	(SWD Pin 1)
   GE3	[Green]	SWDIO	(SWD Pin 7)
   GE4	[Blue]	SWCLK	(SWD Pin 9)
   GND	[Black]	GND	(SWD Pin 4)

2. Although the document states that an external power supply is needed, from experience this is not necessary. The USB port of the computer should provide sufficient power to the 3V3 and +3.3V pins.

For Windows: Redirect SWD Debugger port from Windows to VirtualBox

1. If you're using VirtualBox on Windows, you should configure VirtualBox to allow the Ubuntu Virtual Machine to access the USB port used by the PADI SWD Debugger. Here's how...

2. In the Virtual Machine window, click Devices → USB → USB Settings. Add a USB Device Filter for SEGGER J-Link [0100]. This ensures that the SWD Debugger is always accessible to the Ubuntu Virtual Machine whenever the SWD Debugger is connected to the computer.

   

3. Alternatively, click Devices → USB → SEGGER J-Link [0100] so that it shows a tick. This allows the Ubuntu Virtual Machine to access the SWD Debugger temporarily while the SWD Debugger is connected to the computer.

   

---

Flashing and debugging the PADI from the console

Build flash image from console

1. At the Ubuntu console, run:

   make

2. Check for errors in the build. When the build is complete, you should see:

   ===========================================================
   Image manipulating
   ===========================================================
   ...
   size = 286640
   checksum 1bbbe7d
   ...
   make[1]: Leaving directory '/home/user/rustl8710'
   

3. A sample build log may be found here:
   https://raw.githubusercontent.com/lupyuen/rustl8710/master/log/make.log

Start OpenOCD from console before flashing and debugging

1. Run this command in a new Ubuntu window before writing the flash image or debugging:

   ./start_openocd.sh

2. Keep it running while flashing or debugging. When OpenOCD has been started, you should see:

   Open On-Chip Debugger 0.10.0
   ...
   adapter speed: 4000 kHz
   adapter_nsrst_delay: 100
   cortex_m reset_config sysresetreq
   rtl8710_reboot
   Info : No device selected, using first device.
   Info : J-Link ARM-OB STM32 compiled Aug 22 2012 19:52:04
   Info : Hardware version: 7.00
   Info : VTarget = 3.300 V
   Info : clock speed 4000 kHz
   Info : SWD DPIDR 0x2ba01477
   Info : rtl8710.cpu: hardware has 6 breakpoints, 4 watchpoints
   

3. A sample OpenOCD log may be found here:
   https://github.com/lupyuen/rustl8710/blob/master/log/start_openocd.log

4. If the SWD Debugger is not detected by Ubuntu, install "J-Link Software and Documentation pack for Linux, DEB installer, 64-bit" from
   https://www.segger.com/downloads/jlink#J-LinkSoftwareAndDocumentationPack

   Or copy 99-jlink.rules to /etc/udev/rules.d/

Write flash image from console (using Realtek SDK)

1. At the Ubuntu console, run:

   make flash

2. Check for errors in the log. When the flashing is complete, you should see:

   dump for check
   start addr of dumping$327 = 0x98000000
   end addr of dumping$328 = 0x98050fb0
   Breakpoint 3: file rtl_flash_download.c, line 556.
   Breakpoint 3, RtlFlashProgram () at rtl_flash_download.c:556
   556     in rtl_flash_download.c
   make[1]: Leaving directory '/home/user/rustl8710'
   

3. A sample flash log may be found here:
   https://github.com/lupyuen/rustl8710/blob/master/log/flash.log

Debug flash code from console

1. At the Ubuntu console, run:

   make debug

2. Wait for the GDB prompt before entering debug commands:

   target halted due to debug-request, current mode: Thread
   xPSR: 0x01000000 pc: 0x00000100 msp: 0x1ffffffc
   Breakpoint 1, main () at src/c/src/main.c:16
   16          main_entry();
   (gdb) 
   

3. The GDB Debugger has now paused the execution of the PADI at the main() function in main.c, the point just before our Rust code begins. Enter the step command to continue to the first line of our Rust code:

   (gdb) step
   main_entry () at src/lib.rs:23
   23      pub extern fn main_entry() {
   (gdb)
   

4. To step through each line of the Rust code, keep entering the step command:

   (gdb) step
   24          let mut s = Serial::new();
   (gdb) step
   rustl8710::serial::Serial::new () at src/serial.rs:12
   12                  pipe: serial_t::default()
   (gdb)
   

5. Common GDB commands:

   • step: Execute the current source line, step into functions if present. Same as the step into command in Visual Studio Code.

   • next: Execute the current source line, don't step into functions. Same as the step over command in Visual Studio Code.

   • where: Show stack trace.

   • where full: Show stack trace with local variables.

   • More commands: https://darkdust.net/files/GDB%20Cheat%20Sheet.pdf

6. A sample debug log may be found here:
   https://github.com/lupyuen/rustl8710/blob/master/log/debug.log

7. You may ignore the following messages in the start_openocd console:

   Info : accepting 'gdb' connection on tcp/3333
   undefined debug reason 7 - target needs reset
   Info : SWD DPIDR 0x2ba01477
   Error: Failed to read memory at 0xfffff000
   ...
   target halted due to debug-request, current mode: Thread
   xPSR: 0x01000000 pc: 0x00000100 msp: 0x1ffffffc
   Warn : Receiving data from device timed out, retrying.
   Info : dropped 'gdb' connection
   

Run flash code from console

1. Set the Voltage jumper of PADI Serial Console USB adapter to 3V3

2. Connect the PADI to your computer via the PADI Serial Console USB adapter according to Page 2 of
   http://files.pine64.org/doc/PADI/quick-start-guide/padi-iot-stamp-qsg.pdf

   PADI Serial Console		PADI IoT Stamp
   GND	[Black]	GND
   3V3	[Red]	VDD
   RxD	[Brown]	GA4	(UART2_OUT)
   TxD	[White]	GA0	(UART2_IN)

3. Connect PADI Serial Console to the USB port of your computer to power up the PADI IoT Stamp

4. For Windows: Install and run putty from
   https://www.chiark.greenend.org.uk/~sgtatham/putty/latest.html
   Look for the COM port of the PADI in Device Manager, descibed in Page 4 of
   http://files.pine64.org/doc/PADI/quick-start-guide/padi-iot-stamp-qsg.pdf
   It should look like COM4, COM5, ...

5. For Ubuntu: Run

   sudo cutecom

6. In putty or cutecom, connect to the Windows COM port or Ubuntu serial port (e.g. /dev/ttyUSB0, /dev/ttyUSB1) with these settings:

   • Speed: 38400
   • Data Bits: 8
   • Parity: None
   • Stop Bits: 1
   

7. You are now connected to the UART Serial Console for the PADI. Press a few keys like a b c 1 2 3 and you'll see that the PADI responds with:

   Received: a
   Received: b
   Received: c
   Received: 1
   Received: 2
   Received: 3
   

   

Inspecting the sample flash code

The sample source code is located here:
https://github.com/lupyuen/rustl8710/blob/master/src/rust/src/lib.rs

pub extern fn main_entry() {
    let mut s = Serial::new();
    s.tx_string("Hello from Rust!\n");
    loop {
        let data = s.rx_i32();
        s.tx_string("Received: ");
        s.tx_i32(data);
        s.tx_string("\n");
    }
}

The Rust program reads one character at a time from the UART Serial Console. For every character received, the program prints the character preceded by Received:. The message Hello from Rust! appears as soon as the PADI powers on. Since the serial console is not connected to putty or cutecom during power on, we can't see the first message.

---

Flashing and debugging the PADI from Visual Studio Code

Open the Visual Studio Code workspace:

1. On Ubuntu, install Video Studio Code from
   https://code.visualstudio.com/download

2. Launch Video Studio Code on Ubuntu with the command:

   code

3. Click File → Open Workspace

4. Browse to the rustl8710 folder. Select workspace.code-workspace

Install the following Visual Studio Code extensions:

1. Better TOML (bungcip)
   https://marketplace.visualstudio.com/items?itemName=bungcip.better-toml

2. C/C++ (Microsoft)
   https://marketplace.visualstudio.com/items?itemName=ms-vscode.cpptools

3. GitLens - Git supercharged (Eric Amodio)
   https://marketplace.visualstudio.com/items?itemName=eamodio.gitlens

4. markdownlint (David Anson)
   https://marketplace.visualstudio.com/items?itemName=davidanson.vscode-markdownlint

5. Native Debug (WebFreak)
   https://marketplace.visualstudio.com/items?itemName=webfreak.debug

6. Rust (kalitaalexey)
   https://marketplace.visualstudio.com/items?itemName=kalitaalexey.vscode-rust

7. Rust (rls) (rust-lang)
   https://marketplace.visualstudio.com/items?itemName=rust-lang.rust

8. Tcl (sleutho)
   https://marketplace.visualstudio.com/items?itemName=sleutho.tcl

   

Build flash image from Visual Studio Code

1. Click Tasks → Run Build Task

2. Check for errors in the Build PADI Image terminal window. When the build is complete, you should see:

   ===========================================================
   Image manipulating
   ===========================================================
   ...
   size = 286640
   checksum 1bbbe7d
   ...
   make[1]: Leaving directory '/home/user/rustl8710'
   Terminal will be reused by tasks, press any key to close it.
   

3. A sample build log may be found here:
   https://raw.githubusercontent.com/lupyuen/rustl8710/master/log/make.log

Start OpenOCD from Visual Studio Code before flashing and debugging

1. Before flashing or debugging, start OpenOCD in the background:

   Click Tasks → Run Task → Start OpenOCD

2. Keep it running while flashing or debugging in Visual Studio Code. Check for errors in the Start OpenOCD terminal window. When OpenOCD has been started, you should see:

   Open On-Chip Debugger 0.10.0
   ...
   adapter speed: 4000 kHz
   adapter_nsrst_delay: 100
   cortex_m reset_config sysresetreq
   rtl8710_reboot
   Info : No device selected, using first device.
   Info : J-Link ARM-OB STM32 compiled Aug 22 2012 19:52:04
   Info : Hardware version: 7.00
   Info : VTarget = 3.300 V
   Info : clock speed 4000 kHz
   Info : SWD DPIDR 0x2ba01477
   Info : rtl8710.cpu: hardware has 6 breakpoints, 4 watchpoints
   

3. A sample OpenOCD log may be found here:
   https://github.com/lupyuen/rustl8710/blob/master/log/start_openocd.log

4. If the SWD Debugger is not detected by Ubuntu, install "J-Link Software and Documentation pack for Linux, DEB installer, 64-bit" from
   https://www.segger.com/downloads/jlink#J-LinkSoftwareAndDocumentationPack

Write flash image from Visual Studio Code

1. Check that OpenOCD has been started.

2. Click Tasks → Run Task → Flash PADI

3. Check for errors in the Flash PADI terminal window. When the flashing is complete, you should see:

   dump for check
   start addr of dumping$327 = 0x98000000
   end addr of dumping$328 = 0x98050fb0
   Breakpoint 3: file rtl_flash_download.c, line 556.
   Breakpoint 3, RtlFlashProgram () at rtl_flash_download.c:556
   556     in rtl_flash_download.c
   make[1]: Leaving directory '/home/user/rustl8710'
   Terminal will be reused by tasks, press any key to close it.
   

4. A sample flash log may be found here:
   https://github.com/lupyuen/rustl8710/blob/master/log/flash.log

Debug flash code from Visual Studio Code

1. Check that OpenOCD has been started.

2. Click Debug → Start Debugging

   

3. You may click the debugger toolbar at top right to debug your Rust program:

   Continue	Step Over	Step Into	Step Out	Step Back	Reverse	Restart	Stop

4. The debugger has now paused the execution of the PADI at the main() function in main.c, the point just before our Rust code begins:

   

5. Click the Step Into button to continue to the first line of our Rust code:

   

6. To step through each line of the Rust code, keep clicking the Step Into button:

   

7. You may ignore the following messages in the Start OpenOCD terminal window:

   Info : accepting 'gdb' connection on tcp/3333
   undefined debug reason 7 - target needs reset
   Info : SWD DPIDR 0x2ba01477
   Error: Failed to read memory at 0xfffff000
   ...
   target halted due to debug-request, current mode: Thread
   xPSR: 0x01000000 pc: 0x00000100 msp: 0x1ffffffc
   Warn : Receiving data from device timed out, retrying.
   Info : dropped 'gdb' connection
   

Run flash code from Visual Studio Code

Use the same instructions as "Run Flash Code From Console" above.

---

Other commands

The following commands are useful for creating a full flash image backup (e.g. the factory-installed image) and for restoring the image.

Read flash memory directly (using rtl8710.ocd)

openocd -f interface/jlink.cfg -f rtl8710.ocd \
        -c "init" \
        -c "reset halt" \
        -c "rtl8710_flash_read_id" \
        -c "rtl8710_flash_read dump.bin 0 1048576" \
        -c "shutdown"

Write flash memory image directly (using rtl8710.ocd)

openocd -f interface/jlink.cfg -f rtl8710.ocd \
        -c "init" \
        -c "reset halt" \
        -c "rtl8710_flash_auto_erase 1" \
        -c "rtl8710_flash_auto_verify 1" \
        -c "rtl8710_flash_write dump.bin 0" \
        -c "shutdown"

---

How the build is done

1. A sample build log may be found here:
   https://raw.githubusercontent.com/lupyuen/rustl8710/master/log/make.log

2. The build begins with Xargo compiling the Rust programs and libraries for the PADI. thumbv7m-none-eabi targets the ARM Cortex M3 platform used by PADI.

   ...
   cd src/rust && xargo build --target thumbv7m-none-eabi -v
   ...
   cp src/rust/target/thumbv7m-none-eabi/debug/librustl8710.rlib application/Debug/rust_obj/librustl8710.o
   cp src/rust/target/thumbv7m-none-eabi/debug/deps/libfreertos_rs*.rlib application/Debug/rust_obj/libfreertos_rs.o
   cp ~/.xargo/lib/rustlib/thumbv7m-none-eabi/lib/libcore*.rlib application/Debug/rust_obj/libcore.o
   cp ~/.xargo/lib/rustlib/thumbv7m-none-eabi/lib/liballoc*.rlib application/Debug/rust_obj/liballoc.o
   cp ~/.xargo/lib/rustlib/thumbv7m-none-eabi/lib/libcompiler_builtins*.rlib application/Debug/rust_obj/libcompiler_builtins.o

3. TODO: Xargo is no longer needed for compiling thumbv7m-none-eabi programs:
   https://users.rust-lang.org/t/psa-you-no-longer-need-xargo-to-do-arm-cortex-m-development/16703

4. The Realtek Ameba RTL8710AF SDK then builds the complete flash image by compiling all the necessary system and library files, including drivers and protocols for wifi and all other interfaces:

   ===========================================================
   Build application
   ===========================================================
   ...
   arm-none-eabi-gcc ... -c component/soc/realtek/8195a/cmsis/device/system_8195a.c -o component/soc/realtek/8195a/cmsis/device/system_8195a.o
   arm-none-eabi-gcc ... -c component/common/api/at_cmd/atcmd_ethernet.c -o component/common/api/at_cmd/atcmd_ethernet.o
   arm-none-eabi-gcc ... -c component/common/api/at_cmd/atcmd_lwip.c -o component/common/api/at_cmd/atcmd_lwip.o
   arm-none-eabi-gcc ... -c component/common/api/at_cmd/atcmd_sys.c -o component/common/api/at_cmd/atcmd_sys.o
   ...

5. The Realtek Ameba RTL8710AF SDK links the compiled files into a single image application.axf

   arm-none-eabi-gcc -mcpu=cortex-m3 -mthumb -g ...
       -o application/Debug/bin/application.axf  
       application/Debug/obj/system_8195a.o 
       application/Debug/obj/atcmd_ethernet.o 
       application/Debug/obj/atcmd_lwip.o 
       application/Debug/obj/atcmd_sys.o
       application/Debug/obj/atcmd_wifi.o 
       ... 
       application/Debug/rust_obj/librustl8710.o 
       application/Debug/rust_obj/libfreertos_rs.o 
       application/Debug/rust_obj/libcore.o 
       application/Debug/rust_obj/liballoc.o 
       application/Debug/rust_obj/libcompiler_builtins.o 
       application/Debug/obj/ram_1.r.o
       ...

6. The SDK generates the flash image ram_all.bin by manipulating application.axf:

   ===========================================================
   Image manipulating
   ===========================================================
   arm-none-eabi-nm application/Debug/bin/application.axf | sort > application/Debug/bin/application.nmap
   arm-none-eabi-objcopy -j .image2.start.table -j .ram_image2.text -j .ram_image2.rodata -j .ram.data -Obinary application/Debug/bin/application.axf application/Debug/bin/ram_2.bin
   arm-none-eabi-objcopy -j .sdr_text -j .sdr_rodata -j .sdr_data -Obinary application/Debug/bin/application.axf application/Debug/bin/sdram.bin
   ...
   component/soc/realtek/8195a/misc/iar_utility/common/tools/pick 0x`grep __ram_image2_text_start__ application/Debug/bin/application.nmap | gawk '{print $1}'` 0x`grep __ram_image2_text_end__ application/Debug/bin/application.nmap | gawk '{print $1}'` application/Debug/bin/ram_2.bin application/Debug/bin/ram_2.p.bin body+reset_offset+sig
   b:268460032 s:268460032 e:268746656
   size 286624
   copy size 286624
   component/soc/realtek/8195a/misc/iar_utility/common/tools/pick 0x`grep __ram_image2_text_start__ application/Debug/bin/application.nmap | gawk '{print $1}'` 0x`grep __ram_image2_text_end__ application/Debug/bin/application.nmap | gawk '{print $1}'` application/Debug/bin/ram_2.bin application/Debug/bin/ram_2.ns.bin body+reset_offset
   b:268460032 s:268460032 e:268746656
   size 286624
   copy size 286624
   component/soc/realtek/8195a/misc/iar_utility/common/tools/pick 0x`grep __sdram_data_start__ application/Debug/bin/application.nmap | gawk '{print $1}'` 0x`grep __sdram_data_end__ application/Debug/bin/application.nmap | gawk '{print $1}'` application/Debug/bin/sdram.bin application/Debug/bin/ram_3.p.bin body+reset_offset
   b:805306368 s:805306368 e:805306368
   size 0
   copy size 0
   component/soc/realtek/8195a/misc/iar_utility/common/tools/padding 44k 0xFF application/Debug/bin/ram_1.p.bin
   total 44 k, padding data ff, name application/Debug/bin/ram_1.p.bin
   Original size 15032
   Padding  size 45056
   cat application/Debug/bin/ram_1.p.bin > application/Debug/bin/ram_all.bin
   cat application/Debug/bin/ram_2.p.bin >> application/Debug/bin/ram_all.bin
   if [ -s application/Debug/bin/sdram.bin ]; then cat application/Debug/bin/ram_3.p.bin >> application/Debug/bin/ram_all.bin; fi
   cat application/Debug/bin/ram_2.ns.bin > application/Debug/bin/ota.bin
   if [ -s application/Debug/bin/sdram.bin ]; then cat application/Debug/bin/ram_3.p.bin >> application/Debug/bin/ota.bin; fi
   component/soc/realtek/8195a/misc/iar_utility/common/tools/checksum application/Debug/bin/ota.bin || true
   size = 286640 
   checksum 1bbbe85

---

References

Official PADI docs and downloads, including Realtek Ameba RTL8710AF SDK and its docs:
https://www.pine64.org/?page_id=946

Original rustl8710 article:
https://polyfractal.com/post/rustl8710/

JLink no longer works with the PADI SWD Debugger USB dongle:
https://forum.pine64.org/archive/index.php?thread-4579-2.html

Alternative OpenOCD config (rtl8710.ocd):
https://bitbucket.org/rebane/rtl8710_openocd/src

Using OpenOCD with SWD Transport:
http://openocd.org/doc-release/html/Debug-Adapter-Configuration.html#SWD-Transport

Rust wrapper for FreeRTOS:
https://github.com/hashmismatch/freertos.rs

Xargo cross compiler for Rust:
https://github.com/japaric/xargo

Concurrency and safety in Rust:
https://blog.rust-lang.org/2015/04/10/Fearless-Concurrency.html