====== Lab 02 ======

===== Exercise Objectives =====

  * Introduce WOKWI environment
  * Program various program to control GPIO pins

===== WOKWI =====

  * Open website [[https://wokwi.com/]]
  * Sign up (with Google account) or select Raspberry Pi Pico from available [[https://wokwi.com/pi-pico|templates]]
  * Start coding :-)
  * [[https://drive.google.com/file/d/1ZiCN4bv86OIdtsjvK9UiwqSEIroXmxKz/view?usp=drive_link|video]]

==== Traffic lights ====

<note tip>You can begin from the scratch of inspire yourself from some existing [[https://wokwi.com/projects/380280942145427457|project]].
</note>

=== Tasks ===

  * Connect three (different colors) LEDs to some pins. Be aware, that some of pins are GND.
  * Create the object to control Pins
  * Write program to toggle all LEDs
  * Update program to simulate traffic lights using delays
  * Update program to simulate traffic lights using timer (and state machine)

----

=== Code to control three LEDs ===


<code python>

from machine import Pin
import time

# create object to control the pin
led1 = Pin(0, Pin.OUT)
led2 = Pin(1, Pin.OUT)
led3 = Pin(2, Pin.OUT)

leds = [led1, led2, led3]

while True:
  for i in leds:
    i.toggle()
    time.sleep_ms(1000)
</code>  

=== Code using state machine and timer ===

<code python>
from machine import Pin, Timer
import time
# objects to control GPIO pins
led1 = Pin(0, Pin.OUT)
led2 = Pin(1, Pin.OUT)
led3 = Pin(2, Pin.OUT)
# global variable to keep status of machine
status = 0
# object to control Timer
timer = Timer()

def state(X):
  if X == 0:
    led1.on(); led2.off(); led3.off()
  elif X == 1:
    led1.on(); led2.on(); led3.off()
  elif X == 2:
    led1.off(); led2.off(); led3.on()
  elif X == 3:
    led1.off(); led2.on(); led3.off()

def next_state(timer):
  global status
  state(status % 4)
  status = status + 1

timer.init(freq=1, mode=Timer.PERIODIC, callback=next_state)
</code>