MicroPython Forum (Archive)

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# Example using PWM to fade an LED.

import time
import rp2
from machine import Pin, PWM

# measure time between falling edges
@rp2.asm_pio(set_init=rp2.PIO.IN_HIGH)
def perMeas():
    label('mainloop')
    set(x,0)
    wait(0, pin, 0)
    label('lo_loop')
    jmp(x_dec,'next')
    label('next')
    jmp(pin,'hi')
    jmp('lo_loop')
    label('hi')
    mov(isr,x)
    push()
    jmp('mainloop')
    
# Construct PWM object, with LED on Pin(25).
pwm = PWM(Pin(25))

# Set the PWM frequency.
pwm.freq(10)

# Fade the LED in and out a few times.
duty = 10
direction = 1
# for _ in range(8 * 256):

sm4 = rp2.StateMachine(1, perMeas, freq=200000, in_base=Pin(25)) # pin16 used
sm4.active(1)

while True:
    duty += direction
    if duty > 255:
        duty = 255
        direction = -1
    elif duty < 0:
        duty = 0
        direction = 1
    pwm.duty_u16(duty * duty)
    time.sleep(1.0)

    while sm4.rx_fifo():
        print(2**32-sm4.get(),end=' ')
    else:
        print('empty',end=' ')
    print()    

Code: Select all

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

@rp2.asm_pio(set_init=rp2.PIO.IN_LOW, autopush=True, push_thresh=32)
def period():
    wrap_target()
    set(x, 0)
    wait(0, pin, 0)  # Wait for pin to go low
    wait(1, pin, 0)  # Low to high transition
    label('low_high')
    jmp(x_dec, 'next') [1]  # unconditional
    label('next')
    jmp(pin, 'low_high')  # while pin is high
    label('low')  # pin is low
    jmp(x_dec, 'nxt')
    label('nxt')
    jmp(pin, 'done')  # pin has gone high: all done
    jmp('low')
    label('done')
    in_(x, 32)  # Auto push: SM stalls if FIFO full
    wrap()

@rp2.asm_pio(set_init=rp2.PIO.IN_LOW, autopush=True, push_thresh=32)
def mark():
    wrap_target()
    set(x, 0)
    wait(0, pin, 0)  # Wait for pin to go low
    wait(1, pin, 0)  # Low to high transition
    label('low_high')
    jmp(x_dec, 'next') [1]  # unconditional
    label('next')
    jmp(pin, 'low_high')  # while pin is high
    in_(x, 32)  # Auto push: SM stalls if FIFO full
    wrap()

pin16 = Pin(16, Pin.IN, Pin.PULL_UP)
sm0 = rp2.StateMachine(0, period, in_base=pin16, jmp_pin=pin16)
sm0.active(1)
sm1 = rp2.StateMachine(1, mark, in_base=pin16, jmp_pin=pin16)
sm1.active(1)

pwm = PWM(Pin(17))
pwm.freq(1000)
pwm.duty_u16(0xffff // 3)

# Clock is 125MHz. 3 cycles per iteration, so unit is 24.0ns
def scale(v):
    return (1 + (v ^ 0xffffffff)) * 24e-6  # Scale to ms

while True:
    period = scale(sm0.get())
    mark = scale(sm1.get())
    print(period, mark, mark/period)
    time.sleep(0.2)

Code: Select all

from machine import Pin
import time,utime,rp2

@rp2.asm_pio(set_init=rp2.PIO.IN_HIGH, autopush=True, push_thresh=16) # push() is done automatically win in_()!
def period():
    set(x, 1023)
    in_(x, 16)  # Auto push : SM stalls if FIFO full
    wrap_target()
    nop()
    wrap()

pin16 = Pin(16, Pin.IN, Pin.PULL_UP) 
sm_meas = rp2.StateMachine(0, period, freq=100000, in_base=pin16, jmp_pin=pin16)

sm_meas.active(1)
while True:
    print("\nrestart ... ",end="")
    sm_meas.restart()
    print("got ",end="")
    while sm_meas.rx_fifo()>0:
        period_ticks=sm_meas.get()
        print(period_ticks,end=" ")
    utime.sleep(1)

Code: Select all

MicroPython v1.17 on 2021-09-02; Raspberry Pi Pico with RP2040
Type "help()" for more information.
>>> %Run -c $EDITOR_CONTENT

restart ... got 0 0 
restart ... got 0 
restart ... got 0 

Code: Select all

@rp2.asm_pio(set_init=rp2.PIO.IN_HIGH, autopush=True, push_thresh=32) # push() is done automatically win in_()!
def period():
    set(x, 31)
    in_(x, 32)  # Auto push : SM stalls if FIFO full
    wrap_target()
    nop() [1]
    wrap()