USB serial communication between Raspberry Pi and micro:bit.

MicrobitSerialComm.py

from microbit import *
import music

music.play(["C4:1", "G4:1"])

pot_value = 0
pot_prev = 0
data_in = ''

while True:
    sleep(100)
    
    # Read analog value and send serial uart data to Raspberry Pi
    adc_pot = pin2.read_analog()
    pot_value = int(adc_pot / 125)
    if pot_value != pot_prev:
        print(pot_value)
        pot_prev = pot_value

    # Read serial uart data from Raspberry Pi and control LEDs
    try:
        data_in = uart.read()
        #display.scroll(in_byte)
        
        pin16.write_digital(int(data_in) & 1)
        pin15.write_digital((int(data_in) & 2) >> 1)
        pin14.write_digital((int(data_in) & 4) >> 2)

    except:
        pass

RPiSerialComm.py

from gpiozero import LED, Button, Buzzer
from time import sleep
import serial

led1 = LED(17)
led2 = LED(18)
led3 = LED(27)
led4 = LED(22)
led5 = LED(25)
led6 = LED(12)
led7 = LED(13)
led8 = LED(19)

sw1 = Button(21)
sw2 = Button(16)
sw3 = Button(20)

buzzer = Buzzer(26)

# Replace with your microbit port number
PORT = "/dev/ttyACM1"
BAUD = 115200
s = serial.Serial(PORT)
s.baudrate = BAUD
s.parity   = serial.PARITY_NONE
s.databits = serial.EIGHTBITS
s.stopbits = serial.STOPBITS_ONE
s.timeout  = 1
s.reset_input_buffer()

def leds(no):
    if no >= 1:
        led1.on()
    else:
        led1.off()
    if no >= 2:
        led2.on()
    else:
        led2.off()
    if no >= 3:
        led3.on()
    else:
        led3.off()
    if no >= 4:
        led4.on()
    else:
        led4.off()
    if no >= 5:
        led5.on()
    else:
        led5.off()
    if no >= 6:
        led6.on()
    else:
        led6.off()
    if no >= 7:
        led7.on()
    else:
        led7.off()
    if no >= 8:
        led8.on()
    else:
        led8.off()

def sw1Pressed():
    global ledStatus
    global sw1State
    print("SW1 is pressed")
    sw1State = not sw1State
    if sw1State == True:
        ledStatus = ledStatus + 1
    else:
        ledStatus = ledStatus - 1

def sw2Pressed():
    global ledStatus
    global sw2State
    print("SW2 is pressed")
    sw2State = not sw2State
    if sw2State == True:
        ledStatus = ledStatus + 2
    else:
        ledStatus = ledStatus - 2

def sw3Pressed():
    global ledStatus
    global sw3State
    print("SW3 is pressed")
    sw3State = not sw3State
    if sw3State == True:
        ledStatus = ledStatus + 4
    else:
        ledStatus = ledStatus - 4

sw1.when_pressed = sw1Pressed
sw2.when_pressed = sw2Pressed
sw3.when_pressed = sw3Pressed

sw1State = False
sw2State = False
sw3State = False

ledStatus = 0
prevLedStatus = 0

while True:
    # Read serial uart data from microbit
    try:
        data = s.readline().decode('UTF-8')
        data = int(data)
        print("Receive data: {}".format(data))
        leds(data)
    except:
        pass
    
    # Send serial uart data to microbit
    if ledStatus != prevLedStatus:
        s.write(str(ledStatus).encode('UTF-8'))
        prevLedStatus = ledStatus
    
s.close()