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