From b491967bbd99470632b783ee3bf91914aa692047 Mon Sep 17 00:00:00 2001 From: IhorNehrutsa Date: Fri, 15 Oct 2021 14:04:40 -0700 Subject: esp32/machine_pwm: Implement duty_u16() and duty_ns() PWM methods. The methods duty_u16() and duty_ns() are implemented to match the existing docs. The duty will remain the same when the frequency is changed. Standard ESP32 as well as S2, S3 and C3 are supported. Thanks to @kdschlosser for the fix for rounding in resolution calculation. Documentation is updated and examples expanded for esp32, including the quickref and tutorial. Additional notes are added to the machine.PWM docs regarding limitations of hardware PWM. --- docs/esp32/tutorial/pwm.rst | 106 +++++++++++++++++++++++++++++++++++--------- 1 file changed, 86 insertions(+), 20 deletions(-) (limited to 'docs/esp32/tutorial/pwm.rst') diff --git a/docs/esp32/tutorial/pwm.rst b/docs/esp32/tutorial/pwm.rst index 0c1afb213b..12d10a86b9 100644 --- a/docs/esp32/tutorial/pwm.rst +++ b/docs/esp32/tutorial/pwm.rst @@ -1,4 +1,4 @@ -.. _esp32_pwm: +.. _esp32_pwm: Pulse Width Modulation ====================== @@ -11,7 +11,7 @@ compared with the length of a single period (low plus high time). Maximum duty cycle is when the pin is high all of the time, and minimum is when it is low all of the time. -More comprehensive example with all 16 PWM channels and 8 timers:: +* More comprehensive example with all 16 PWM channels and 8 timers:: from machine import Pin, PWM try: @@ -29,21 +29,87 @@ More comprehensive example with all 16 PWM channels and 8 timers:: except: pass -Output is:: - - PWM(pin=15, freq=100, duty=64, resolution=10, mode=0, channel=0, timer=0) - PWM(pin=2, freq=100, duty=128, resolution=10, mode=0, channel=1, timer=0) - PWM(pin=4, freq=200, duty=192, resolution=10, mode=0, channel=2, timer=1) - PWM(pin=16, freq=200, duty=256, resolution=10, mode=0, channel=3, timer=1) - PWM(pin=18, freq=300, duty=320, resolution=10, mode=0, channel=4, timer=2) - PWM(pin=19, freq=300, duty=384, resolution=10, mode=0, channel=5, timer=2) - PWM(pin=22, freq=400, duty=448, resolution=10, mode=0, channel=6, timer=3) - PWM(pin=23, freq=400, duty=512, resolution=10, mode=0, channel=7, timer=3) - PWM(pin=25, freq=500, duty=576, resolution=10, mode=1, channel=0, timer=0) - PWM(pin=26, freq=500, duty=640, resolution=10, mode=1, channel=1, timer=0) - PWM(pin=27, freq=600, duty=704, resolution=10, mode=1, channel=2, timer=1) - PWM(pin=14, freq=600, duty=768, resolution=10, mode=1, channel=3, timer=1) - PWM(pin=12, freq=700, duty=832, resolution=10, mode=1, channel=4, timer=2) - PWM(pin=13, freq=700, duty=896, resolution=10, mode=1, channel=5, timer=2) - PWM(pin=32, freq=800, duty=960, resolution=10, mode=1, channel=6, timer=3) - PWM(pin=33, freq=800, duty=1023, resolution=10, mode=1, channel=7, timer=3) + Output is:: + + PWM(Pin(15), freq=100, duty=64, resolution=10, mode=0, channel=0, timer=0) + PWM(Pin(2), freq=100, duty=128, resolution=10, mode=0, channel=1, timer=0) + PWM(Pin(4), freq=200, duty=192, resolution=10, mode=0, channel=2, timer=1) + PWM(Pin(16), freq=200, duty=256, resolution=10, mode=0, channel=3, timer=1) + PWM(Pin(18), freq=300, duty=320, resolution=10, mode=0, channel=4, timer=2) + PWM(Pin(19), freq=300, duty=384, resolution=10, mode=0, channel=5, timer=2) + PWM(Pin(22), freq=400, duty=448, resolution=10, mode=0, channel=6, timer=3) + PWM(Pin(23), freq=400, duty=512, resolution=10, mode=0, channel=7, timer=3) + PWM(Pin(25), freq=500, duty=576, resolution=10, mode=1, channel=0, timer=0) + PWM(Pin(26), freq=500, duty=640, resolution=10, mode=1, channel=1, timer=0) + PWM(Pin(27), freq=600, duty=704, resolution=10, mode=1, channel=2, timer=1) + PWM(Pin(14), freq=600, duty=768, resolution=10, mode=1, channel=3, timer=1) + PWM(Pin(12), freq=700, duty=832, resolution=10, mode=1, channel=4, timer=2) + PWM(Pin(13), freq=700, duty=896, resolution=10, mode=1, channel=5, timer=2) + PWM(Pin(32), freq=800, duty=960, resolution=10, mode=1, channel=6, timer=3) + PWM(Pin(33), freq=800, duty=1023, resolution=10, mode=1, channel=7, timer=3) + +* Example of a smooth frequency change:: + + from utime import sleep + from machine import Pin, PWM + + F_MIN = 500 + F_MAX = 1000 + + f = F_MIN + delta_f = 1 + + p = PWM(Pin(5), f) + print(p) + + while True: + p.freq(f) + + sleep(10 / F_MIN) + + f += delta_f + if f >= F_MAX or f <= F_MIN: + delta_f = -delta_f + + See PWM wave at Pin(5) with an oscilloscope. + +* Example of a smooth duty change:: + + from utime import sleep + from machine import Pin, PWM + + DUTY_MAX = 2**16 - 1 + + duty_u16 = 0 + delta_d = 16 + + p = PWM(Pin(5), 1000, duty_u16=duty_u16) + print(p) + + while True: + p.duty_u16(duty_u16) + + sleep(1 / 1000) + + duty_u16 += delta_d + if duty_u16 >= DUTY_MAX: + duty_u16 = DUTY_MAX + delta_d = -delta_d + elif duty_u16 <= 0: + duty_u16 = 0 + delta_d = -delta_d + + See PWM wave at Pin(5) with an oscilloscope. + +Note: the Pin.OUT mode does not need to be specified. The channel is initialized +to PWM mode internally once for each Pin that is passed to the PWM constructor. + +The following code is wrong:: + + pwm = PWM(Pin(5, Pin.OUT), freq=1000, duty=512) # Pin(5) in PWM mode here + pwm = PWM(Pin(5, Pin.OUT), freq=500, duty=256) # Pin(5) in OUT mode here, PWM is off + +Use this code instead:: + + pwm = PWM(Pin(5), freq=1000, duty=512) + pwm.init(freq=500, duty=256) -- cgit v1.2.3