cardboard_bot.py

from microbit import *

pin0.set_analog_period(10)
pin1.set_analog_period(10)
motor_direction = 0
zero_pos = 155
f_pos_1 = 165
f_pos_2 = 145
r_pos_1 = 0
r_pos_2 = 0

while True:
  if (motor_direction != 1):    
    if ((button_a.is_pressed() == True) & (button_b.is_pressed() == True)):
      pin0.write_analog(f_pos_1)
      pin1.write_analog(f_pos_2)
      motor_direction = 1
      display.clear()
      display.show(Image.ARROW_N)
      
  if (motor_direction != 5):
    if ((button_a.is_pressed() == False) & (button_b.is_pressed() == False)):
      pin0.write_analog(zero_pos)
      pin1.write_analog(zero_pos)
      motor_direction = 5
      display.clear()
      display.scroll("Sensor error - robot STOP !!!", delay=100)
  
  if (motor_direction != 4):
    if ((button_a.is_pressed() == False) & (button_b.is_pressed() == True)):
      pin0.write_analog(zero_pos)
      pin1.write_analog(f_pos_2)
      motor_direction = 4
      display.clear()
      display.show(Image.ARROW_NW)
      
  if (motor_direction != 3):
    if ((button_b.is_pressed() == False) & (button_a.is_pressed() == True)):
      pin0.write_analog(f_pos_1)
      pin1.write_analog(zero_pos)
      motor_direction = 3
      display.clear()
      display.show(Image.ARROW_NE)