import time
from machine import Pin
import rp2

time.sleep(0.1)  # Wait for USB to become ready

print("Hello, Pi Pico!")

# Pin definitions
led_pin = Pin(2, Pin.OUT)
step_a_minus = Pin(21, Pin.OUT)
step_a_plus = Pin(20, Pin.OUT)
step_b_plus = Pin(19, Pin.OUT)
step_b_minus = Pin(18, Pin.OUT)

# Step sequence for the stepper motor
step_sequence = [
    (1, 0, 1, 0),  # A+ and B+
    (0, 1, 1, 0),  # A- and B+
    (0, 1, 0, 1),  # A- and B-
    (1, 0, 0, 1),  # A+ and B-
]

# Step index to track the current step in the sequence
current_step = 0

# Function to rotate the stepper motor by one step
def stepper_rotate_one_step(clockwise=True):
    global current_step
    if clockwise:
        current_step = (current_step + 1) % 4
    else:
        current_step = (current_step - 1) % 4

    # Apply the current step
    step = step_sequence[current_step]
    step_a_plus.value(step[0])
    step_a_minus.value(step[1])
    step_b_plus.value(step[2])
    step_b_minus.value(step[3])

# PIO program to read data from UART TX FIFO (state machine)
@rp2.asm_pio(out_init=(rp2.PIO.OUT_LOW,))
def uart_rx():
    pull()  # Pull data from the RX FIFO into the state machine
    mov(isr, x)  # Move the received value into the ISR register

# Create a state machine and associate it with the PIO program
sm = rp2.StateMachine(0, uart_rx, freq=1000000)  # Removed `in_pin` argument

# Function to check if the character 'A' was received
def detect_char():
    try:
        return sm.get() == ord('A')  # Compare received data with ASCII 'A'
    except IndexError:
        return False  # If no data is available in the RX FIFO

# Start the state machine
sm.active(1)

# Main loop
while True:
    # If 'A' is received, rotate clockwise, else rotate counter-clockwise
    if detect_char():  # Character 'A' received
        print("Detected 'A'. Rotating clockwise.")
        led_pin.value(0)  # Turn ON LED (clockwise)
        stepper_rotate_one_step(clockwise=True)  # Rotate motor clockwise
    else:
        print("No 'A' detected. Rotating counter-clockwise.")
        led_pin.value(1)  # Turn OFF LED (counter-clockwise)
        stepper_rotate_one_step(clockwise=False)  # Rotate motor counter-clockwise

    # Step rate is 10 Hz (0.1 seconds per step)
    time.sleep(0.1)  # Step delay for 10 Hz