AnalogWrite for ESP32 and ESP32-S2 with LEDC PWM. Includes PWM Phase Control, DAC and Smart GPIO resource management.

@Dlloydev First of all, thank you for making a really cool library. Making analogWrite() supported is a big step towards making programs run on both esp32s and standard Arduino boards more easily!

I was looking at the output of the Fade example with an oscilloscope and noticed the signal wasn't quite what I would expect. Each time analogWrite was called to change the duty cycle on the pin, it seems the pin goes low for approximately 200 microseconds. This interrupts the otherwise good 5kHz PWM signal and means that even if the signal is set to 100% there will be intervals where the pin is LOW after each time analogWrite is called. This issue could cause unexpected results in any program where analogWrite is called frequently.

Is ledcSetup getting called every time analogWrite is? That might be what's causing the issue because when I have used ledcSetup once then only ledcWrite later I don't get the dips. Would it be possible to check if the channel, resolution, or frequency needs to be changed? If only the duty cycle needs to be changed then I don't think ledcSetup needs to be called.

Please let me know if I can help in any way. Thanks, joshua-8

Thanks for this library! My use case is fading up to 36 LED strips from an ESP32.

I want to ask about it's operation because I did not fully understand it from the description. Taking for example an ESP32-S2 will it provide PWM capabilities for the pins: 1- 14, 21, 33-42, 45, so a total of 26 pins. This much is clear.

What's not clear, for me, is: can I assign individual duty-cycles (PWM values) for each of these 26 pins so that I can fade each LED on it's own ? (the 8 PWM channels stuff gets me a bit confused) Is there any way for this library to support more than 26 pins?

Hi, I'm trying to use the libray to control a servo, but it doesn't work when i'm using the pwm.setServo function. It's not in the keywords.txt file :/

For a simple 8 bit 20KHz fan PWM on pin 22 of a DOIT ESP32 DEVKIT V1 :

In setup() I have:

  analogWrite(FAN, 0, 20000, 8); 

In loop()I have:

  fan_pwm =  ... // a function of temperature
  analogWrite(FAN, fan_pwm);

This works as expected but if I do an over the air update the PWM value gets stuck until I cycle the power and then it works again.

Do I need to do something in the OTA code to stop the PWM or reinitialise it?

First of all, thank you so much for fixing the issue with ledcSetup getting called repeatedly! That issue is gone for me now, but I found another thing: When trying to use this library as a direct replacement for the standard analogWrite function, I noticed that the output was never going above a few percent on. Usually analogWrite has an 8 bit resolution, but this library seems to use 13 bits as default. It's really great that you provide the option to set higher resolutions since ESP32s can support that, but if it wouldn't be too difficult and if I'm not missing something, changing the default to 8 to be the same as the normal analogWrite would make this library even easier to use. Thanks, joshua-8

I think a tone() function would be nice to have in the next update (4.2.0)

Initial thoughts on how this could work ...

• use the existing pin management features of this library
• can auto-attach or attach to specified channel
• this function to be non-blocking
• the frequency and resolution will affect a secondary channel. Therefore, ensure that this secondary channel is still useable for LED fade control (variable duty).
• Add an ESP32 example showing use tone, servo and led fade control.

file esp32_pwmWrite.ino

C:\Users\xxxxx\Documents\Arduino\libraries\ESP32_ESP32S2_AnalogWrite\src\pwmWrite.cpp: In member function 'float Pwm::write(uint8_t, int32_t, float, uint8_t, uint32_t)': C:\Users\xxxxx\Documents\Arduino\libraries\ESP32_ESP32S2_AnalogWrite\src\pwmWrite.cpp:216:7: error: 'ledc_channel_config_t' has no non-static data member named 'flags' }; ^ exit status 1 Error compiling for board ESP32 Dev Module.

Very nice library!

Do you have suggestions on how to manage dead time?

I.e. when building a half/full bridge, you need to 180 degree phase shifted PWM signals but you also need dead time so that the low side shuts off and then the high side turns on with a delay and then the high side turns off and the low side turns on with a delay. Otherwise you create a dead short. Normally this is about 40-60 ns.

It would be awesome if this was a single function in this library something like: halfBridge(PinHigh, PinLo, dutyCycle, Frequency, deadTime);

Where dutyCycle would automatically calculate based on the frequency (typically in the 2.2 mhz range)

For a full bridge (hard switching zvs, boost/buck) fullBridge(pinBuckHigh, pinBuckLo, pinBoostHight, pinBoostLo, dutyCycle, frequency, deadTime)

Where dutyCycle could be positive or negative.

It would be nice to be able to assign a ledc channel to a pin. I want to use pin 13 but Channel 0 and 2 are already occupied by another libraries and awGetChannel(13) returns -1. Is there a workaround / solution?

Hi @Dlloydev, I was experimenting with using ledc to control a servo, and I found that using ledcSetup seems to cause a pulse to be output on an attached pin. It's more of an issue for servo control (it causes a twitch) than the use case of analogWrite (it wouldn't affect controlling an led), but I thought I'd let you know about this in case you plan to output servo signals (actually, it would be cool if the library would have a function that makes it easy to output servo signal PWM, but that's off topic now). Here's the code I used:

#include "analogWrite.h"

#define analogPin 33 //pin to analogWrite to
#define triggerPin 26 //pin that triggers oscilloscope when resolution changed

void setup() {
  pinMode(triggerPin,OUTPUT);
  digitalWrite(triggerPin,LOW);
  analogWrite(analogPin, 50);
  delay(1000); //wait a bit to get some pulses at the first resolution
  digitalWrite(triggerPin,HIGH); //trigger oscilloscope
  analogWriteResolution(analogPin, 10); //change resolution
}
void loop(){
  delay(1);
}

it produced the following signal:

I found a potential fix for this issue: I was able to change frequency with ledcSetup without getting the pulse by using ledcDetachPin, then calling ledcSetup, and then calling ledcAttachPin.

Since the pulse only happens once when changing resolution this is really not at all a critical bug to fix, but I thought you might want to know about it.

Thank you for spending so much time making great opensource libraries!

-joshua-8

I found that analogWriteResolution() always returns 0. According to the documentation it should return pow(2, resolution).

https://github.com/Dlloydev/ESP32-ESP32S2-AnalogWrite/blob/6474044198650928d9417d0373725ade0fdbd398/analogWrite.cpp#L244

So I assume the term should be either 1 << (resolution & 0xF); or just 1 << resolution;

Thank you for your efforts Jan