Board support crate for the Longan Nano board
Rust 1.36 or a newer toolchain. e.g.
rustup default stable
corecrate) for the RISC-V target. Run:
rustup target add riscv32imac-unknown-none-elf
- RISC-V toolchain (e.g. from SiFive)
dfu-util, the entire RISC-V toolchain is not necessary. Only
objcopy from riscv-binutils-gdb is needed.
It can be compiled with the following commands:
git clone https://github.com/sifive/riscv-binutils-gdb.git cd riscv-binutils-gdb ./configure --target=riscv64-unknown-elf --disable-werror --with-python=no --disable-gdb --disable-sim --disable-libdecnumber --disable-libreadline --with-expat=yes --with-mpc=no --with-mpfr=no --with-gmp=no make
It will provide the
binutils/objcopy tool needed to convert the compiled Rust binary into
firmware.bin (note: this works on arm64 as well).
If you have a GD32VF103CB chip on your board, edit
.cargo/config and replace
To build all the provided examples run
cargo build --examples --release --all-features
Using dfu-util for Flashing
The GD32VF103 contains a DFU compatible bootloader which allows to program the firmware of your longan-nano without additional hardware like a JTAG adapter; instead just using an ordenary USB-C cable. You can use dfu-util or the vendor supplied tool to flash the firmware.
Unfortunately, some versions of this chip shipped with a buggy bootloader and it won't report the correct parameters to flash it sucessfully. As of May 2020, the most recent version of dfu-util from the git repository contains a workaround. Make sure you use an up-to-date version. See this issue for details.
Steps to flash an example via DFU:
- Extract the binary
riscv-nuclei-elf-objcopy -O binary target/riscv32imac-unknown-none-elf/release/blinky firmware.bin
- Flash using
Keep the BOOT0 button pressed while power-up or while pressing and releaseing the reset button. Then run
dfu-util -a 0 -s 0x08000000:leave -D firmware.bin
Ensure that dfu-util uses a page size of 1024; either because your GD32VF103 has a bootloader without the the aforementioned bug, or because the output reads
[...] Device returned transfer size 2048 DfuSe interface name: "Internal Flash " Found GD32VF103, which reports a bad page size and count for its internal memory. Fixed layout based on part number: page size 1024, count 128. Downloading to address = 0x08000000, size = 23784 [...]
Using OpenOCD for Flashing and Debugging
Start openocd assuming you have Sipeed JTAG adapter:
/path/to/openocd -f sipeed-jtag.cfg -f openocd.cfg
Run one of the examples:
cargo run --example blinky
cargo run --release --example ferris --features lcd
Using RV-LINK for Flashing and Debugging
RV-LINK is a Chinese firmware, similar to Black Magic Probe (BMP). It supports the Longan Nano, allowing to use one Longan Nano board as a debug probe for another one. It can be built & flashed via PlatformIO. Check out the latest version to ensure that the code compiles:
> git clone https://gitee.com/zoomdy/RV-LINK > cd RV-LINK > git tag v0.0.1 v0.1 v0.2 # <- seems to be the latest tag, so let's check this out > git checkout tags/v0.2
PlatformIO allows building & flashing of firmware with a single command. To do so, the board needs to be in bootloader mode (DFU mode). The board boots to bootloader mode if the bootloader button is pressed while powering it up (e.g. by plugging it in). However, it is also possible to enter bootloader mode without un- and replugging the board: press the boot button, press the reset button, release the reset button and finally release the boot button while the board is plugged in.
> pio run -t upload # put the board in bootloader mode before
Once RV-LINK is flashed to your probe, connect the eight debug pins on the probe with the debug pins on the debug target. Ensure that you connect the pins according to this table:
|Probe Pin||Target Pin|
After you connected the debug probe to your host, a new serial port shows up.
You can connect GDB to this serial port as an
predictable behavior when multiple serial devices are present (and hence
/dev/ttyACM0 is not necessarily the RV-LINK device),
udev offers id symlinks.
However you may also use
/dev/ttyACM0 or even
COMx if you run Windows.
> gdb (gdb) target extended-remote /dev/serial/by-id/usb-RV-LINK_Longan_Nano_GD32XXX-3.0.0-7z8x9yer-if00
To flash the firmware, execute
load in GDB:
> gdb target/remote/debug/demo (gdb) target extended-remote /dev/ttyACM0 (gdb) monitor reset halt (gdb) load (gdb) monitor reset
To improve your workflow, you can put the aforementioned GDB commands in
debug.gdb file and add these lines to
[target.riscv32imac-unknown-none-elf] runner = 'gdb -command=debug.gdb'
cargo run --target riscv32imac-unknown-none-elf will automatically
launch GDB, flash your firmware on the target and provide you with a full debug
You can infer the current status of the board by observing the blinking pattern of the green LED:
|Blink Behavior||Probe Status|
|Short pulse, on for 100ms, off for 900ms||GDB is not connected|
|Slow flashing, on for 500ms, off for 500ms||GDB is connected and the debugged MCU is in halt state|
|Fast blinking, on for 100ms, off for 100ms||GDB is connected, and the debugged MCU is running|
|Long pulse, on for 900ms, off for 100ms||RV-LINK has failed. Retry after resetting RV-LINK|
Using serial for Flashing
Using a TTL-to-USB adapter, one can flash the firmware to the device over a serial connection:
$ stm32flash -g 0x08000000 -b 115200 -w firmware.bin /dev/ttyUSB0
which sets the base address (
-g 0x08000000) for the firmware to the start of main flash.
The baud rate (
-b 115200), firmware image (
-w firmware.bin), and serial port (
/dev/ttyUSB0) are set next.
The serial port may vary machine to machine, so select the port that makes sense.
Make sure the device is writeable by the current user, or run
stm32flash as root.
Copyright 2019-2020 RISC-V team
Permission to use, copy, modify, and/or distribute this software for any purpose with or without fee is hereby granted, provided that the above copyright notice and this permission notice appear in all copies.
THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.