communicate between stm32 bluepill and rasspberry pi
  There are several ways to communicate between an STM32 Bluepill board and a Raspberry Pi:

1. UART (Serial): Both the STM32 Bluepill and Raspberry Pi have a UART (Universal Asynchronous Receiver-Transmitter) interface. You can use a serial cable to connect the two boards and communicate using the serial console.
2. SPI: The STM32 Bluepill and Raspberry Pi both have SPI (Serial Peripheral Interface) interfaces. You can use the SPI bus to communicate between the two boards.
3. I2C: The STM32 Bluepill and Raspberry Pi both have I2C (Inter-Integrated Circuit) interfaces. You can use the I2C bus to communicate between the two boards.
4. Ethernet: If you have an Ethernet connection between the two boards, you can use TCP/IP to communicate between them.
5. Wi-Fi: If the Raspberry Pi has a Wi-Fi module installed, you can use Wi-Fi to communicate between the two boards.
6. BLE (Bluetooth Low Energy): If the STM32 Bluepill has a BLE module installed, you can use BLE to communicate between the two boards.
7. USB OTG:
A way to communicate between an STM32 BluePill and a Raspberry Pi is through the use of a serial connection. The STM32 BluePill can be connected to the Raspberry Pi through the serial connection and commands can be sent from the Raspberry Pi to the STM32 BluePill.