esp32: PWM duty will be changed when changing the frequency if more than one channel is used. #8345

Dreagonmon · 2022-02-23T18:12:42Z

After upgrading mpy from 1.17 to 1.18, my buzzer can't play low frequency sounds any more.

With further test, it shows that the pwm has no output when frequencies < 611Hz.

from machine import PWM, Pin
pwm = PWM(Pin(5)) # also tested with Pin(2)
pwm.duty(512)
pwm.freq(611) # it works, digital multimeters shows freq 1222Hz
pwm.freq(610) # no pwm output, digital multimeters says freq is 0

And after switching back to mpy 1.17, pwm.freq(610) works fine. I'v tested with another board and I still got the same result. I'm sure this is an issue introduced by v1.18.

The text was updated successfully, but these errors were encountered:

xky183 · 2022-02-26T10:43:38Z

meet same problem by v1.18，work fine by v1.17

robert-hh · 2022-02-26T10:53:19Z

Fixed since a while. Please use a recent nightly build, and ignore the "unstable" label. The nightly builds are tested the same way than the release build.

xky183 · 2022-02-26T12:36:23Z

Fixed since a while. Please use a recent nightly build, and ignore the "unstable" label. The nightly builds are tested the same way than the release build.

Thank you very much，I just tested the version "esp32-20220226-unstable-v1.18-160-g0a217624e.bin", it can work in 1Hz now, but... the duty will be changed when changing the freq.

>>> 
>>> pwm0
PWM(Pin(0), freq=2, duty=512, resolution=16, (duty=50.00%, resolution=0.002%), mode=0, channel=0, timer=0)
>>> pwm0.freq(200)
>>> pwm0
PWM(Pin(0), freq=200, duty=512, resolution=16, (duty=50.00%, resolution=0.002%), mode=0, channel=0, timer=0)
>>> pwm0.freq(2000)
>>> pwm0
PWM(Pin(0), freq=2003, duty=1024, resolution=15, (duty=100.00%, resolution=0.003%), mode=0, channel=0, timer=2)
>>> pwm0.duty(512)
>>> pwm0
PWM(Pin(0), freq=2003, duty=512, resolution=15, (duty=50.00%, resolution=0.003%), mode=0, channel=0, timer=2)
>>> pwm0.freq(2000)
>>> pwm0
PWM(Pin(0), freq=20000, duty=8192, resolution=11, (duty=800.00%, resolution=0.049%), mode=0, channel=0, timer=1)
>>> pwm0.duty(512)
>>> pwm0.freq(20000)
>>> pwm0
PWM(Pin(0), freq=20000, duty=512, resolution=11, (duty=50.00%, resolution=0.049%), mode=0, channel=0, timer=1)
>>> pwm0.freq(2000)
>>> pwm0
PWM(Pin(0), freq=2003, duty=32, resolution=15, (duty=3.13%, resolution=0.003%), mode=0, channel=0, timer=2)
>>> pwm0.duty(512)
>>> pwm0
PWM(Pin(0), freq=2003, duty=512, resolution=15, (duty=50.00%, resolution=0.003%), mode=0, channel=0, timer=2)
>>> pwm0.freq(200)
>>> pwm0
PWM(Pin(0), freq=200, duty=256, resolution=16, (duty=25.00%, resolution=0.002%), mode=0, channel=0, timer=0)
>>> pwm0.duty(512)
>>> pwm0
PWM(Pin(0), freq=200, duty=512, resolution=16, (duty=50.00%, resolution=0.002%), mode=0, channel=0, timer=0)
>>> pwm0.freq(20)
>>> pwm0
PWM(Pin(0), freq=20, duty=512, resolution=16, (duty=50.00%, resolution=0.002%), mode=0, channel=0, timer=0)
>>> pwm0.freq(2)
>>> pwm0
PWM(Pin(0), freq=2, duty=512, resolution=16, (duty=50.00%, resolution=0.002%), mode=0, channel=0, timer=0)
>>>

Dreagonmon · 2022-02-26T12:58:03Z

maybe #8306 is the related issue.

I created this issue and closed it soon when I realized that this is fixed in the nightly build. but it seems not really fixed.

robert-hh · 2022-02-26T13:06:32Z

No. It is not. That is something which show up only once after hard reset. I just tested you sequence with my own builds, and it works fine. I just downloaded the nightly build and verify, which esp-idf and version is used.

robert-hh · 2022-02-26T13:15:42Z

I cannot verify your findings. Everything looks as intended. Both the reporting in the print and the actual signal are fine.

MicroPython v1.18 on 2022-02-26; ESP32 module (spiram) with ESP32
Type "help()" for more information.
>>> p0=PWM(Pin(0), 2, duty=512)
>>> p0
PWM(Pin(0), freq=2, duty=512, resolution=16, (duty=50.00%, resolution=0.002%), mode=0, channel=0, timer=0)
>>> p0.freq(200)
>>> p0
PWM(Pin(0), freq=200, duty=512, resolution=16, (duty=50.00%, resolution=0.002%), mode=0, channel=0, timer=0)
>>> p0.freq(2000)
>>> p0
PWM(Pin(0), freq=2003, duty=512, resolution=15, (duty=50.00%, resolution=0.003%), mode=0, channel=0, timer=0)
>>> p0.freq(20000)
>>> p0
PWM(Pin(0), freq=20000, duty=512, resolution=11, (duty=50.00%, resolution=0.049%), mode=0, channel=0, timer=0)
>>> p0.freq(2000)
>>> p0
PWM(Pin(0), freq=2003, duty=512, resolution=15, (duty=50.00%, resolution=0.003%), mode=0, channel=0, timer=0)
>>> p0.freq(200)
>>> p0
PWM(Pin(0), freq=200, duty=512, resolution=16, (duty=50.00%, resolution=0.002%), mode=0, channel=0, timer=0)
>>> p0.freq(2)
>>> p0
PWM(Pin(0), freq=2, duty=512, resolution=16, (duty=50.00%, resolution=0.002%), mode=0, channel=0, timer=0)
>>> import platform
>>> platform.platform()
'MicroPython-1.18.0-xtensa-IDFv4.2.2-with-newlib3.0.0'
>>>

xky183 · 2022-02-27T06:38:05Z

I test twice，
at the first time，only use one PWM0 channel，it works well。
at the second time，use PWM0,PWM2,PWM4 channel，it seems timers for each pwm channel will be changed when changing the freq, and it will cause the changing of duty , maybe the problem is the counter of the timer is not set right value，

`>>> 
>>> from machine import PWM
>>> pwm0 = PWM(Pin(0), freq=2, duty=512)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'Pin' isn't defined
>>> from machine import Pin
>>> pwm0 = PWM(Pin(0), freq=2, duty=512)
>>> pwm0
PWM(Pin(0), freq=2, duty=512, resolution=16, (duty=50.00%, resolution=0.002%), mode=0, channel=0, timer=0)
>>> pwm0.freq(20)
>>> pwm0
PWM(Pin(0), freq=20, duty=512, resolution=16, (duty=50.00%, resolution=0.002%), mode=0, channel=0, timer=0)
>>> pwm0.freq(200)
>>> pwm0
PWM(Pin(0), freq=200, duty=512, resolution=16, (duty=50.00%, resolution=0.002%), mode=0, channel=0, timer=0)
>>> pwm0.freq(2000)
>>> pwm0
PWM(Pin(0), freq=2003, duty=512, resolution=15, (duty=50.00%, resolution=0.003%), mode=0, channel=0, timer=0)
>>> pwm0.freq(20000)
>>> pwm0
PWM(Pin(0), freq=20000, duty=512, resolution=11, (duty=50.00%, resolution=0.049%), mode=0, channel=0, timer=0)
>>> pwm0.freq(200000)
>>> pwm0
PWM(Pin(0), freq=200000, duty=512, resolution=8, (duty=50.00%, resolution=0.391%), mode=0, channel=0, timer=0)
>>> pwm0.freq(20000)
>>> pwm0
PWM(Pin(0), freq=20000, duty=512, resolution=11, (duty=50.00%, resolution=0.049%), mode=0, channel=0, timer=0)
>>> pwm0.freq(2000)
>>> pwm0
PWM(Pin(0), freq=2003, duty=512, resolution=15, (duty=50.00%, resolution=0.003%), mode=0, channel=0, timer=0)
>>> pwm0.freq(200)
>>> pwm0
PWM(Pin(0), freq=200, duty=512, resolution=16, (duty=50.00%, resolution=0.002%), mode=0, channel=0, timer=0)
>>> pwm0.freq(20)
>>> pwm0
PWM(Pin(0), freq=20, duty=512, resolution=16, (duty=50.00%, resolution=0.002%), mode=0, channel=0, timer=0)
>>> pwm0.freq(2)
>>> pwm0
PWM(Pin(0), freq=2, duty=512, resolution=16, (duty=50.00%, resolution=0.002%), mode=0, channel=0, timer=0)
>>> ets Jun  8 2016 00:22:57

rst:0x1 (POWERON_RESET),boot:0x13 (SPI_FAST_FLASH_BOOT)
configsip: 0, SPIWP:0xee
clk_drv:0x00,q_drv:0x00,d_drv:0x00,cs0_drv:0x00,hd_drv:0x00,wp_drv:0x00
mode:DIO, clock div:2
load:0x3fff0030,len:4540
ho 0 tail 12 room 4
load:0x40078000,len:12344
ho 0 tail 12 room 4
load:0x40080400,len:4124
entry 0x40080680
MicroPython v1.18 on 2022-02-26; ESP32 module with ESP32
Type "help()" for more information.
>>> from machine import Pin
>>> from machine import PWM
>>> pwm0 = PWM(Pin(0), freq=2, duty=512)
>>> pwm2 = PWM(Pin(2), freq=200, duty=512)
>>> pwm4 = PWM(Pin(4), freq=2000, duty=512)
>>> pwm0
PWM(Pin(0), freq=2, duty=512, resolution=16, (duty=50.00%, resolution=0.002%), mode=0, channel=0, timer=0)
>>> pwm0.freq(20)
>>> pwm0
PWM(Pin(0), freq=20, duty=512, resolution=16, (duty=50.00%, resolution=0.002%), mode=0, channel=0, timer=0)
>>> pwm0.freq(200)
>>> pwm0
PWM(Pin(0), freq=200, duty=512, resolution=16, (duty=50.00%, resolution=0.002%), mode=0, channel=0, timer=1)
>>> pwm0.freq(2000)
>>> pwm0
PWM(Pin(0), freq=2003, duty=1024, resolution=15, (duty=100.00%, resolution=0.003%), mode=0, channel=0, timer=2)
>>> pwm0.duty(512)
>>> pwm0
PWM(Pin(0), freq=2003, duty=512, resolution=15, (duty=50.00%, resolution=0.003%), mode=0, channel=0, timer=2)
>>> pwm0.freq(20000)
>>> pwm0
PWM(Pin(0), freq=20000, duty=512, resolution=11, (duty=50.00%, resolution=0.049%), mode=0, channel=0, timer=0)
>>> pwm0.freq(200000)
>>> pwm0
PWM(Pin(0), freq=200000, duty=512, resolution=8, (duty=50.00%, resolution=0.391%), mode=0, channel=0, timer=0)
>>> pwm0.freq(20000)
>>> pwm0
PWM(Pin(0), freq=20000, duty=512, resolution=11, (duty=50.00%, resolution=0.049%), mode=0, channel=0, timer=0)
>>> pwm0.freq(2000)
>>> pwm0
PWM(Pin(0), freq=2003, duty=32, resolution=15, (duty=3.13%, resolution=0.003%), mode=0, channel=0, timer=2)
>>> pwm0.duty(512)
>>> pwm0
PWM(Pin(0), freq=2003, duty=512, resolution=15, (duty=50.00%, resolution=0.003%), mode=0, channel=0, timer=2)
>>> pwm0.freq(200)
>>> pwm0
PWM(Pin(0), freq=200, duty=256, resolution=16, (duty=25.00%, resolution=0.002%), mode=0, channel=0, timer=1)
>>> pwm0.duty(512)
>>> pwm0
PWM(Pin(0), freq=200, duty=512, resolution=16, (duty=50.00%, resolution=0.002%), mode=0, channel=0, timer=1)
>>> pwm0.freq(20)
>>> pwm0
PWM(Pin(0), freq=20, duty=512, resolution=16, (duty=50.00%, resolution=0.002%), mode=0, channel=0, timer=0)
>>> pwm0.freq(2)
>>> pwm0
PWM(Pin(0), freq=2, duty=512, resolution=16, (duty=50.00%, resolution=0.002%), mode=0, channel=0, timer=0)
>>> import platform
>>> platform.platform()
'MicroPython-1.18.0-xtensa-IDFv4.2.2-with-newlib3.0.0'
>>> 
>>> 
>>> `

xky183 · 2022-02-27T06:48:53Z

maybe #8306 is the related issue.

I created this issue and closed it soon when I realized that this is fixed in the nightly build. but it seems not really fixed.

could you reopen this issue? thanks

robert-hh · 2022-02-27T12:09:30Z

You are right. If more than one channel is used, there will be issues with the duty cycle. The basic PR which changed that behavior is #7817. The PR message explains the function and one can see the root of the problem, which is also visible in your log. If a channel's frequency is set to a frequency used by the other channel, it uses this channels timer. That does not take care of potentially different duty cycles.
Dropping the timer re-use mechanism makes the PWM work as intended. However, it is then again limited to 8 channels.

Dreagonmon · 2022-02-27T12:18:09Z

could you reopen this issue? thanks

sure

robert-hh · 2022-02-27T14:12:34Z

So I made a small change to the code which forces the duty rate to be set on frequency changes. That was omitted when setting to a frequency which was already used in a different channel. The timer for that channel was reused, but still the duty rate had to be adapted. The change is based on a different PR I made earlier, and by chance it fixes #8306 as well. Output from going though the same series as @xky183 above:

MicroPython v1.18-160-g0a217624e-dirty on 2022-02-27; ESP32 module (spiram) with ESP32
Type "help()" for more information.
>>> import platform
>>> platform.platform()
'MicroPython-1.18.0-xtensa-IDFv4.2.2-dirty-with-newlib3.0.0'
>>> pwm0 = PWM(Pin(0), freq=2, duty=512)
>>> pwm2 = PWM(Pin(22), freq=200, duty=512)
>>> pwm4 = PWM(Pin(4), freq=2000, duty=512)
>>> pwm0
PWM(Pin(0), freq=2, duty=512, resolution=18, (duty=50.00%, resolution=0.000%), mode=0, channel=0, timer=0)
>>> pwm0.freq(20)
>>> pwm0
PWM(Pin(0), freq=20, duty=512, resolution=20, (duty=50.00%, resolution=0.000%), mode=0, channel=0, timer=0)
>>> pwm0.freq(200)
>>> pwm0
PWM(Pin(0), freq=200, duty=512, resolution=18, (duty=50.00%, resolution=0.000%), mode=0, channel=0, timer=1)
>>> pwm0.freq(2000)
>>> pwm0
PWM(Pin(0), freq=2003, duty=512, resolution=15, (duty=50.00%, resolution=0.003%), mode=0, channel=0, timer=2)
>>> pwm0.freq(20000)
>>> pwm0
PWM(Pin(0), freq=20000, duty=512, resolution=11, (duty=50.00%, resolution=0.049%), mode=0, channel=0, timer=0)
>>> pwm0.freq(2000)
>>> pwm0
PWM(Pin(0), freq=2003, duty=512, resolution=15, (duty=50.00%, resolution=0.003%), mode=0, channel=0, timer=2)
>>> pwm0.freq(200)
>>> pwm0
PWM(Pin(0), freq=200, duty=512, resolution=18, (duty=50.00%, resolution=0.000%), mode=0, channel=0, timer=1)
>>> pwm0.freq(20)
>>> pwm0
PWM(Pin(0), freq=20, duty=512, resolution=20, (duty=50.00%, resolution=0.000%), mode=0, channel=0, timer=0)
>>> pwm0.freq(2)
>>> pwm0
PWM(Pin(0), freq=2, duty=512, resolution=18, (duty=50.00%, resolution=0.000%), mode=0, channel=0, timer=0)
>>>

If setting the frequency to a value used already by an existing timer, this timer will be used. But still, the duty cycle for that channel may have to be changed. Fixes issues #8306 and #8345.

dpgeorge · 2022-03-07T02:40:28Z

Fixed by 55a0125

Forbidden pins are now correctly "in use" on ESP

Dreagonmon closed this as completed Feb 23, 2022

Dreagonmon reopened this Feb 27, 2022

Dreagonmon changed the title ~~esp32: PWM has no output when frequencies < 611Hz.~~ esp32: PWM duty will be changed when changing the frequency if more than one channel is used. Feb 27, 2022

This was referenced Feb 27, 2022

esp32: Always set the duty cycle when setting the frequency. #8361

Closed

V1.18 breaks microservo (MG90S) functionality through PWM on ESP32. Works on Pico though. #8377

Closed

dpgeorge closed this as completed Mar 7, 2022

Wind-stormger pushed a commit to BPI-STEAM/micropython that referenced this issue Sep 14, 2023

Merge pull request micropython#8345 from tannewt/s3_watchdog

442f84d

Forbidden pins are now correctly "in use" on ESP

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esp32: PWM duty will be changed when changing the frequency if more than one channel is used. #8345

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esp32: PWM duty will be changed when changing the frequency if more than one channel is used. #8345

esp32: PWM duty will be changed when changing the frequency if more than one channel is used. #8345

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