from machine import Pin
import rp2
import time

# Define the PIO program
@rp2.asm_pio(
    autopull=True,    # Enable autopull to automatically pull data from the TX FIFO
    pull_thresh=32,
    out_init=(rp2.PIO.OUT_LOW,) * 4,
    out_shiftdir=rp2.PIO.SHIFT_LEFT, 
        # Set the threshold for autopull to 32 bits
)
def blink_led():
    pull(ifempty)
    out(pins, 4)     # Output 32 bits of data from the shift register to the pin
    set(y, 31)        # Set delay counter to 31
    label("delay")
    nop() [31]        # Small delay loop
    jmp(y_dec, "delay")  # Decrement counter and loop until zero

# Create a Pin object for the LED
led_pin = Pin(0, Pin.OUT)  # LED connected to GPIO 25

# Initialize the State Machine with the blink_led program
sm = rp2.StateMachine(0, blink_led, freq=20000, out_base=led_pin)
sm.active(1)

# Main loop
while True:
    # Load data into the TX FIFO to control the LED
    sm.put(0x1)  # Load 32 bits of data to turn the LED on
    time.sleep(1)       # Wait for 1 second
    sm.put(0x2)  # Load 32 bits of data to turn the LED off
    time.sleep(1)       # Wait for 1 second