CH592 Makefile Template

A Makefile template for the openwch/ch592 to remove the need for MounRiver Studio.
Based on rgoulter/ch592-ble-hid-keyboard-example

The elf can be flashed to the CH592 using wchisp. (Enter the CH592 bootloader by holding down BOOT when connecting it using USB).
The SDK for CH592 from the openwch EVT is vendored under sdk/. (Encoding has been changed from gbk to utf-8).

make to complie
make clean to clean/remove the compiled elf
make flash to flash
make f to compile and flash.

To install the toolchain using Gentoo native tools
crossdev --target riscv-none-elf --with-arch=rv32imca_zicsr --with-abi=ilp32
echo "cross-riscv-none-elf/newlib nano" >> /etc/portage/package.use/embedded
emerge -a cross-riscv-none-elf/newlib