diff options
Diffstat (limited to 'docs/esp32')
| -rw-r--r-- | docs/esp32/quickref.rst | 22 | ||||
| -rw-r--r-- | docs/esp32/tutorial/pwm.rst | 106 |
2 files changed, 100 insertions, 28 deletions
diff --git a/docs/esp32/quickref.rst b/docs/esp32/quickref.rst index 7391a4aa4b..97b6fba38d 100644 --- a/docs/esp32/quickref.rst +++ b/docs/esp32/quickref.rst @@ -218,20 +218,24 @@ range from 1Hz to 40MHz but there is a tradeoff; as the base frequency *increases* the duty resolution *decreases*. See `LED Control <https://docs.espressif.com/projects/esp-idf/en/latest/api-reference/peripherals/ledc.html>`_ for more details. -Currently the duty cycle has to be in the range of 0-1023. -Use the ``machine.PWM`` class:: +Use the :ref:`machine.PWM <machine.PWM>` class:: from machine import Pin, PWM - pwm0 = PWM(Pin(0)) # create PWM object from a pin - pwm0.freq() # get current frequency (default 5kHz) - pwm0.freq(1000) # set frequency - pwm0.duty() # get current duty cycle (default 512, 50%) - pwm0.duty(200) # set duty cycle - pwm0.deinit() # turn off PWM on the pin + pwm0 = PWM(Pin(0)) # create PWM object from a pin + pwm0.freq() # get current frequency (default 5kHz) + pwm0.freq(1000) # set PWM frequency from 1Hz to 40MHz + pwm0.duty() # get current duty cycle, range 0-1023 (default 512, 50%) + pwm0.duty(256) # set duty cycle from 0 to 1023 as a ratio duty/1023, (now 25%) + pwm0.duty_u16(2**16*3//4) # set duty cycle from 0 to 65535 as a ratio duty_u16/65535, (now 75%) + pwm0.duty_u16() # get current duty cycle, range 0-65535 + pwm0.duty_ns(250_000) # set pulse width in nanoseconds from 0 to 1_000_000_000/freq, (now 25%) + pwm0.duty_ns() # get current pulse width in ns + pwm0.deinit() # turn off PWM on the pin pwm2 = PWM(Pin(2), freq=20000, duty=512) # create and configure in one go + print(pwm2) # view PWM settings ESP chips have different hardware peripherals: @@ -251,6 +255,8 @@ but only 8 different PWM frequencies are available, the remaining 8 channels mus have the same frequency. On the other hand, 16 independent PWM duty cycles are possible at the same frequency. +See more examples in the :ref:`esp32_pwm` tutorial. + ADC (analog to digital conversion) ---------------------------------- 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) |