from machine import Pin
from time import sleep_ms

ledRed = Pin (3, Pin.OUT)
ledGreen = Pin (1, Pin.OUT)
ledYellow = Pin (2, Pin.OUT)

while True:
  ledGreen.on()
  sleep_ms(3000)
  ledGreen.off()

  ledYellow.on()
  sleep_ms(2000)
  ledYellow.off()
  
  ledRed.on()
  sleep_ms(3000)
  ledRed.off()