46 lines
1.3 KiB
Python
46 lines
1.3 KiB
Python
|
# Example of using PIO for PWM, and fading the brightness of an LED
|
||
|
|
|
||
|
|
from machine import Pin
|
||
|
|
from rp2 import PIO, StateMachine, asm_pio
|
||
|
|
from time import sleep
|
||
|
|
|
||
|
|
|
||
|
|
@asm_pio(sideset_init=PIO.OUT_LOW)
|
||
|
|
def pwm_prog():
|
||
|
|
# fmt: off
|
||
|
|
pull(noblock) .side(0)
|
||
|
|
mov(x, osr) # Keep most recent pull data stashed in X, for recycling by noblock
|
||
|
|
mov(y, isr) # ISR must be preloaded with PWM count max
|
||
|
|
label("pwmloop")
|
||
|
|
jmp(x_not_y, "skip")
|
||
|
|
nop() .side(1)
|
||
|
|
label("skip")
|
||
|
|
jmp(y_dec, "pwmloop")
|
||
|
|
# fmt: on
|
||
|
|
|
||
|
|
|
||
|
|
class PIOPWM:
|
||
|
|
def __init__(self, sm_id, pin, max_count, count_freq):
|
||
|
|
self._sm = StateMachine(sm_id, pwm_prog, freq=2 * count_freq, sideset_base=Pin(pin))
|
||
|
|
# Use exec() to load max count into ISR
|
||
|
|
self._sm.put(max_count)
|
||
|
|
self._sm.exec("pull()")
|
||
|
|
self._sm.exec("mov(isr, osr)")
|
||
|
|
self._sm.active(1)
|
||
|
|
self._max_count = max_count
|
||
|
|
|
||
|
|
def set(self, value):
|
||
|
|
# Minimum value is -1 (completely turn off), 0 actually still produces narrow pulse
|
||
|
|
value = max(value, -1)
|
||
|
|
value = min(value, self._max_count)
|
||
|
|
self._sm.put(value)
|
||
|
|
|
||
|
|
|
||
|
|
# Pin 25 is LED on Pico boards
|
||
|
|
pwm = PIOPWM(0, 25, max_count=(1 << 16) - 1, count_freq=10_000_000)
|
||
|
|
|
||
|
|
while True:
|
||
|
|
for i in range(256):
|
||
|
|
pwm.set(i**2)
|
||
|
|
sleep(0.01)
|