dmatest.py

# RP2 DMA tests based on following projects
# - https://github.com/rkompass/RPi2040_mPy
# - https://github.com/jbentham/pico

import time
from array import array

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

from rp2_dma import RP2_Dma
import rp_devices as devs

# setup ADC
# - GP26 generates high-side voltage of a potentiometer
v1 = Pin(26, Pin.OUT)
v1.value(1)
a1 = ADC(27)

# for direct memory access
clk = devs.CLK_DEVICE
adc = devs.ADC_DEVICE

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

def mem2mem():
  gc.collect()

  sarr = array('i', (i for i in range(-100, 100)))
  darr = array('L', (0 for i in range(200)))

  print(darr)
  dma = RP2_Dma(sarr,  darr)
  dma.start()
  while dma.busy():
    pass
  dma.deinit()
  print(darr)

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

def adcstart():
  # clear
  adc.CS_REG = adc.FCS_REG = 0

  # overclock by 5x to 240MHz (48MHz * 5)
  # https://forums.raspberrypi.com/viewtopic.php?t=340691
  machine.freq(240_000_000)
  clk.CLK_ADC_CTRL.AUXSRC = 1

  # enable and select a channel
  adc.CS.EN = 1
  adc.CS.AINSEL = 1 # ADC_CHAN

  # sample once to test
  #adc.CS.START_ONCE = 1
  #print(adc.RESULT_REG)

  # configure sampling rate (0=fastest)
  # period = 1 + INT(bit 24:8) + FRAC(bit 7:0) / 256
  adc.DIV_REG = 0xFFFFFF

  # configure FIFO for DMA
  adc.FCS.EN = adc.FCS.DREQ_EN = 1
  adc.FCS.THRESH = adc.FCS.OVER = adc.FCS.UNDER = 1

  # bitshift result to fit in a byte
  adc.FCS.SHIFT = 1

  # clear FIFO
  while adc.FCS.LEVEL:
    x = adc.FIFO_REG

  adc.CS.START_MANY = 1

def adcstop():
  adc.CS.START_MANY = 0

  # wait for last conversion to finish
  while adc.CS.READY == 0:
    pass

  # clear FIFO
  while adc.FCS.LEVEL:
    x = adc.FIFO_REG

def adc2mem():
  gc.collect()

  sarr = a1
  darr = array('B', range(8192))

  dma = RP2_Dma(sarr, darr, dsize=0)
  dma.start()
  adcstart()
  while dma.busy():
    pass
  dma.deinit()
  adcstop()
  print(darr)

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

@asm_pio(push_thresh=32, in_shiftdir=PIO.SHIFT_LEFT, out_shiftdir=PIO.SHIFT_RIGHT)
def sm_gen():
  set(x, 0)
  wrap_target()
  # increment with x + 1 = ~((~x) - 1)
  mov(x, invert(x))
  jmp(x_dec, 'here')
  label('here')
  mov(x, invert(x)) # invert(x_dec) compiles, but generates wrong hex
  mov(isr, x) [31]
  # send data
  push(noblock)

def pio2mem():
  gc.collect()

  # restore default clock
  machine.freq(125_000_000)

  sm = StateMachine(0, sm_gen, freq=2000)
  arr = array('L', range(128))
 
  dma = RP2_Dma(sm, arr)

  dma.start()
  sm.active(1)
  while dma.busy():
    pass
  dma.deinit()
  sm.active(0)
  print(arr)

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