Swindle CH32V3x DFU bootloader

This is a "small" bootloader for the CH32V3x chips from WCH. It takes about 13 kB and is being built on top of tinyUSB.

The downloaded application must be linked to be at 0x4000 (i.e. base +16 kB)

There are several ways to enter DFU:

• There is a signature in ram upon reboot (0xDEADBEEFCC00FFEEULL at the beginning of RAM)
• The pin PB7 or PB14 is pulled down to ground
• The signature of the main firmware is invalid

While in DFU, the leds connected to PB13, PC13 and/or PA8 will blink

Firmware signature

The layout is as follows :

• 0000 : Reset instruction (usuall j reset vector)
• 0004 : firmware size in bytes
• 0008 : xxhash32 hash of the firmware

If firmware size is 0x1234 and xxhash is 0x5678, the hash check is skipped.

Building

Edit platformConfig to point for your toolchain.

The one i use is a recent version of clang/riscv32 with picolibc.

Using

dfu-util -d 1d50:6030  -s 0x0004000:leave -D binaryfile