mirror of
https://github.com/tillitis/tillitis-key1.git
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5c50a2b5de
- Add CTS signals let the FPGA and CH552 signal each other that
it is OK send UART data.
- Update the CH552 rx and frame handling logic.
- Fix minor spelling errors and indentation
CH552 USB-to-Serial firmware
Toolchain setup
SDCC:
sudo apt install build-essential sdcc
chprog (for flashing the firmware to a device):
cd ~
sudo apt install libusb-1.0-0-dev
git clone https://github.com/ole00/chprog.git
cd chprog
./build_linux.sh
sudo cp chprog /usr/local/bin
Usage
Build the firmware using a default serial number:
make
Flash the firmware to a device:
make flash_patched
Re-programming the firmware
By design, once the USB to serial firmware is loaded onto the chip, there isn't an intended way to reflash it using only software. However, if 3.3V is applied to the D+ line through a 10K resistor during power-up, then the CH552 will enter bootloader mode, and a new firmware can be programmed onto the chip. Note that the CH552 flash is only guaranteed for a few hundred flash cycles.