Sipeed Longan Nano
The Sipeed Longan Nano is a development board built around a GD32VF103xx MCU. The GD32VF103xx is a GigaDevice MCU with a RISC-V core and an architecture which generally assembles a STM32 MCU.
This page contains noted on how to get a full featured development environment - including (important dammit!) single step debugging - up and running.
Pinout
DFU
The GD32VF103 on the Longan Nano board, like STM32 MCUs has got a built-in system bootloader, which can be activated by holding down the Boot0 button during reset. Contrary to the STM32F103 on Blue Pill boards, this bootloader appears to support DFU.
Adding a UDEV rule to make it readable:
# make this usb device accessible for users, used in WebUSB
# change the mode so unprivileged users can access it, insecure rule, though
SUBSYSTEMS=="usb", ATTR{idVendor}=="28e9", ATTR{idProduct}=="0189", MODE:="0666"
the device is recognized by dfu-util:
lth@ncpws04:~/tmp/mylifeline$ dfu-util -l dfu-util 0.9 Copyright 2005-2009 Weston Schmidt, Harald Welte and OpenMoko Inc. Copyright 2010-2016 Tormod Volden and Stefan Schmidt This program is Free Software and has ABSOLUTELY NO WARRANTY Please report bugs to http://sourceforge.net/p/dfu-util/tickets/ Found DFU: [28e9:0189] ver=0100, devnum=23, cfg=1, intf=0, path="2-4.5.3", alt=0, name="@Internal Flash /0x08000000/128*001Kg", serial="??"
It is working although it is a bit weird they decided to treat the entire flash as one block of 128 kB. According to the User Manual the flash _can_ be erased per 1 kB page.
DIY JTAG
In this case we will be using a home developed development board, the Green Pill as a JTAG programmer. Our Green Pill board is largely compatible with a traditional Blue Pill.
| Name | Green Pill | Longan Nano |
|---|---|---|
| TDI | PB15 | jTDI |
| TDO | PB14 | jTDO |
| TCK | PB13 | jTCK |
| TMS | PB4 | jTMS |
