Introduction

Pi-KVM is a Raspberry Pi based open source KVM implementation. It can support USB keyboard and mouse emulation through USB HID. It currently uses AVR-based HID implementation. However, I only have STM32F103 BluePill board available. So I decided to do a simlar implementation using cheap BluePill. This repo contains the HID emulation source code for my implementation on STM32F103. It has been tested on Pi-KVM, and it worked well for me.

Build Instrucitons

Comping Pi-KVM HID emulator has been tested with Ubuntu 20.04 distribution. Please make sure you have arm-non-eabi-gcc toolchain installed. To compile:

    make clean
    make

The final generated image will be located at ./out/pikvm_hid.bin. This image needs to be flashed to STM32F103 flash address 0x8000000.

Program BluePill

• Enable boot mode to boot from ROM
  • Set jumper BOOT0 to position 1 (3.3v)
• Connect USB UART adaptor to Blue Pill UART1
  • Host TXD to STM32F103 RXD (PA10)
  • Host RXD to STM32F103 TXD (PA9)
  • Host GND to STM32F103 GND
• Flash binary to BluePill. Run following command:
  • sudo python ./script/stmloader.py -p /dev/ttyUSB0 -f F1 -e -w -v ./out/pikvm_hid.bin
• Enable boot mode to normal mode
  • Set jumper BOOT0 to position 0 (GND)

Connect to PiPVM

Pi-KVM communicate with HID emulator through primary UART. It is GPIO 14 (TX, Pin 8) and GPIO 15 (RX, Pin 10) on Raspberry Pi 40-pin connector. For BluePill HID emulator, it uses STM32F103 UART3 (TX PB10 and RX PB11) for Pi-KVM communication. So they need to be connected as below:

• RPI TX (Pin 8) <=> BluePill RX PB11
• RPI RX (Pin 10) <=> BluePill TX PB10
• RPI GND (Pin 6) <=> BluePill GND

References

This project reused some souce code from:

• https://github.com/STMicroelectronics/STM32CubeF1
• https://github.com/IntergatedCircuits/USBDevice
• https://github.com/navilera/Navilos