Use the Raspberry Pi 5 debug UART port (Serial0 ttyAMA10) or the traditional 40 pin GPIO UART port (ttyAMA0) to send serial data. Data is sent to a phone through FTDI cable and USB OTG adapter. Data is also sent to a Xiao SAMD21 chip in keyboard mode. This technique has also been demonstrated to work on Raspberry Pi 4, Orange Pi 5, and Teensy 3.6. The Raspberry Pi 5 is running the Bookworm 64 bit desktop operating system. All baud rates are 115200.
Correction: The diode used was 1N4004.
Raspberry Pi 5 documentation:
https://www.raspberrypi.com/documenta...
new uart port cable: https://www.digikey.com/en/products/d...
Copy the c_send5.cpp and arduino program for Xiao SAMD21: https://github.com/solarsamuel/send_s...
Xiao SAMD21: https://www.seeedstudio.com/Seeeduino...
FTDI cable: https://www.amazon.com/dp/B00HKJOVK4/...
pi pinout: https://www.raspberrypi.com/documenta...
USB OTG adapter: https://www.amazon.com/ThunderboltCo...