# Inspired by https://github.com/pimoroni/pimoroni-pico/blob/8ca47d640523cfb6c3ab262992574dfcfa8527fd/drivers/st7789/st7789_parallel.pio
# rp2.dma docs at https://github.com/micropython/micropython/pull/7670/files
# https://docs.micropython.org/en/latest/library/rp2.PIO.html

import rp2
from machine import Pin

d0 = 0
wr = 8 # GPIO pin number of the write strobe
iterations = 0

def tx_done(arg=None):
    global iterations
    iterations +=1
    print(iterations)

@rp2.asm_pio(out_init=[rp2.PIO.OUT_LOW]*8, sideset_init=rp2.PIO.OUT_LOW, out_shiftdir=rp2.PIO.SHIFT_RIGHT, autopull=True, pull_thresh=8)
def _program():
    wrap_target()
    out(pins, 8)  .side(0) [4]   # Output the next 8 bits in the fifo and strobe the WR pin
    nop()         .side(1) [4]
    wrap()
    # The state machine will automatically pull the next byte from the FIFO, and push it to the output shift register.
    # This will continue until the FIFO is empty, at which point the state machine will stop.

# pio_num is index of the PIO block being used, sm_num is the state machine in that block.
# my_state_machine is an rp2.PIO() instance.
pio_num = 0
sm_num = 0
# my_state_machine = rp2.PIO(pio_num)
sm = rp2.StateMachine((pio_num*4)+sm_num, _program, freq=2000, sideset_base=Pin(wr), out_base=Pin(d0))
sm.active(True)

def transmit(data):
    sm.put(data)
    while sm.tx_fifo():
        pass
    tx_done()

###############################################
tx_fifo_reg = 0x50200000 + 0x010

DATA_REQUEST_INDEX = (pio_num << 3) + sm_num

d = rp2.DMA()
ctrl_noswap = d.pack_ctrl(
        size=0,  # Transfer bytes, rather than words, 
        inc_write=False,  # don't increment the write address
        treq_sel=DATA_REQUEST_INDEX,  # pace the transfer.
        irq_quiet=False,  # Generate IRQs when the transfer is complete.
        bswap=False,  # Whether to byte-swap the data.  Defaults to True.
        # The following fields are defaults, and don't need to be specified.
        enable=True,
        high_pri=False,
        inc_read=True,
        ring_size=0,
        ring_sel=0,
        chain_to=0,
        sniff_en=False,
        write_err=False,
        read_err=False,
    )

ctrl_swap = d.pack_ctrl(default=ctrl_noswap, bswap=True)

def transmit_dma(data):
    d.config(read=src_data, write=tx_fifo_reg, count=len(src_data), ctrl=ctrl_noswap, trigger=False)
    d.irq(handler=tx_done, hard=False)
    d.active(True)

###############################################

src_data = bytearray([i for i in range(256)])

transmit(src_data)