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I try to setup a 10bit pwm with analogWriteResolution(LED_R, 10); but I get the following output:

[esp32-hal-ledc.c:793] analogWriteResolution(): analogWrite resolution cant be set due to selected frequency! Try to adjust frequency first

then I tried to explicitely set the frequency analogWriteFrequency(LED_R,1000);

then I get an additional message:

[esp32-hal-ledc.c:785] analogWriteFrequency(): analogWrite frequency cant be set due to selected resolution! Try to adjust resolution first

void setup() {
  ledcSetClockSource(LEDC_USE_APB_CLK);
  analogWriteFrequency(LED_R,1000);
  analogWriteFrequency(LED_G,1000);
  analogWriteFrequency(LED_B,1000);
  analogWriteResolution(LED_R, 10);
  analogWriteResolution(LED_G, 10);
  analogWriteResolution(LED_B, 10);
}

I really do not understand the problem. 10bit @ 1khz requires a timerfrequency of 1Mhz which should be achievable without problems.

my platormio.ini

[env:esp32]

platform =  https://github.com/pioarduino/platform-espressif32/releases/download/stable/platform-espressif32.zip
board = upesy_wroom
board_build.mcu = esp32

board_build.f_cpu = 240000000L

framework = arduino
monitor_speed = 115200
monitor_filters = esp32_exception_decoder
#build_type = debug
#upload_port = COM6
board_build.filesystem = littlefs

build_unflags = -std=gnu++11
                -std=c++11

build_flags =
    -std=c++17
    -std=gnu++17
Improve this question
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  • First, what pins are you using? Second, what if you used 'ledcAttach(..)' and set the resolution and freqeuncy at the same time? This might give a less contradictory error message than the two you're getting from breaking this into two steps. Commented Jul 23 at 13:49
  • Pins are 0,4,5. Using ledc-API seems to work correctly - so most probably some bug in the Framework-Library?! but using the esp specific lib function means I would have to change all components from the arduino functions to the esp-specific ones Commented Jul 23 at 14:23
  • Yeah I would agree it's a bug, or some non trivial expectation of how those functions would be called. Is there some reason you don't want to use the esp-specific libraries? Your platormio.ini already specifies an esp for the platform, and your already calling an ledc function with 'ledcSetClockSource(..)'. Doing a little searching around I don't see why your custom setting of the freq and resolution isn't working as intended. But, the ledc api does seem to accomplish the same thing. Commented Jul 23 at 15:23
  • @hcheung what does the analogReadResolution has to do with this? Commented Jul 24 at 20:25
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