Code of MeArmMicroBit to read the Serial port and Drive the servos

MeArmMicroBit.py

# Add your Python code here. E.g.
from microbit import *
import time

###### Initialization of the hardware ######

# Turn off display to use display pins as GPIO
display.off()

# initialize the pins to control the Servos
gripper = pin16
right = pin15
left = pin14
base = pin13
servos = [right, left, base, gripper]
for servo in servos:
    servo.set_analog_period_microseconds(20000)
    servo.write_analog(76)

# initialize serial communication (UART over USB)
uart.init(baudrate=115200)

# Input string
inStr = None

# list of values for all 4 servos (4 unsigned integers)
servoValues = [] 
def inStr2servoValues():
    """
    split and cast the string into integer numbers
    """
    global servoValues, inStr
    servoValues = [int(a) for a in inStr.split(',')]


def parseInputStr():
    """
    filter the string input based on the starting and ending byte
    The string input should be comma separated and starting with `s` and ending with `e`
    It is not being checked that it is comma separated but it should be.
    example of string: "s19,80,60,110e"
    Returns True if this sequence of string is complete. Otherwise False
    """
    global inStr
    msg = uart.read(1)
    ch = str(msg, 'UTF-8')
    if ch == 's':
        inStr = str()
    elif ch == 'e' and len(inStr)!= 0:
        inStr2servoValues()
        inStr = None
        return True
    elif inStr != None:
        inStr += ch
    return False


def updateServos():
    """
    Update servos and generate the PWMs
    """
    global servoValues, servos
    for i in range(4):
        servos[i].write_analog(servoValues[i])

# Main Loop
while True:
    # check if there is any serial character availble 
    if (uart.any()):
        # reads and parse the character
        if(parseInputStr()):
            if(len(servoValues) == 4):
                # update the servos
                updateServos()