NOTE!!! LINE 18 SHOULD BE:                 ser.write(b"all\n")


Find Code and Diagrams at: https://www.elithecomputerguy.com/2020/12/arduino-bidirectional-serial-communication-with-raspberry-pi/

You can send data to a Raspberry Pi from an Arduino, have the Pi compute the data and use “intelligence” to send the Arduino a command. This allows you to fully use a Pi as a “Compute Module” for the Arduino with the ability to access databases, data-stores, API’s and anything else a “real” computer can do.

Prerequisites:

Analog Temperature Sensor with Arduino
Raspberry Pi – How to Begin Coding Python on Raspberry Pi
Arduino – Send Commands with Serial Communication
Arduino – Send Serial Commands from Raspberry Pi
Arduino – Read Serial Communication with Raspberry Pi
Functional Parts in the Project:

Arduino Uno – https://store.arduino.cc/usa/arduino-uno-rev3
560 Piece Jumper Wire Kit – https://amzn.to/2MsCLjL
220 Ohm Resistors – https://amzn.to/2RiiMD9
Breadboard Kit – https://amzn.to/2Xih5ei
LED Kit – https://amzn.to/2Rjhs2N
Analog Temperature Sensor – https://amzn.to/2Rkkl3k
Raspberry Pi
USB Cable