from machine import Pin
from rp2 import asm_pio, PIO, StateMachine

pin13 = Pin(13, Pin.IN, Pin.PULL_DOWN)
pin14 = Pin(14, Pin.IN, Pin.PULL_DOWN)
pin15 = Pin(15, Pin.IN, Pin.PULL_DOWN)

@asm_pio(out_init = (PIO.OUT_LOW, ) *4, set_init = PIO.OUT_LOW, out_shiftdir = PIO.SHIFT_RIGHT)
def pio_prog():
    label("start")
    mov(x,0xff)                 # Init Counter
    wrap_target()
    label("display")            
    mov(pins,x)                 # Output Counter
    set(y,16)                   # Delay
    label("dly")
    nop()[31]
    jmp(y_dec,"dly")
    label("readAgain")          # Read Button Inputs
    in_(null,32)
    in_(pins,3)
    mov(y,isr)
    jmp(not_y,"readAgain")      # No Buttons Pressed, Read Again
    mov(osr,y)
    out(y,1)
    jmp(not_y,"dec_x")          # Decrement Button Pressed ?
    out(y,1)
    jmp(not_y,"inc_x")          # Increment Button Pressed ?
    jmp("readAgain")            # If not, Read Again
    label("inc_x")          
    mov(x, invert(x))           # Invert X Register, Twos Compliment
    jmp(x_dec, "next")          # Decrement X Register 
    label("next")
    mov(x, invert(x))           # Invert X Register, Twos Compliment
    jmp("display")              # Jump back up to Display
    label("dec_x")
    jmp(x_dec,"display")        # Decrement X Register
    jmp("display")              # Jump Back Up to Display
    wrap()

sm0 = StateMachine(0, pio_prog, freq = 2000, out_base = Pin(0), in_base = pin13)
sm0.active(1)

while True :
    sleep(0.1)