ledcWriteTone() always uses 10 bit resolution

[vvb333007]

Board

ESP32-WROOM-32D

Device Description

devkit

Hardware Configuration

tiny blue led connected to GPIO2

Version

v3.0.4

IDE Name

ArduinoIDE

Operating System

windows 10

Flash frequency

80

PSRAM enabled

no

Upload speed

115200

Description

ledcWriteTone() configures ledc channel to requested frequency but assumes 10 bit resolution.
As result any attempt to use ledcWriteTone() for frequencies above 78 kHz result in error messages:

E (93107) ledc: requested frequency and duty resolution can not be achieved, try reducing freq_hz or duty_resolution. div_param=0
[ 92088][E][esp32-hal-ledc.c:262] ledcWriteTone(): ledcWriteTone configuration f ailed!

Interestingly, that setting resolution to 8 bit and doing ledcWrite(); ledcWriteTone() the same
message appears BUT PWM generation starts: i can see it by attached led. In particular the above
messages happened when i attempted to set 300kHz frequency and duty=1. I connected a scope and I see that PWM generation happens at exactly 300kHz but still I see these error messages. This happens with the code attached, Arduino Core 3.04 and latest as well.

Sketch

static int tone_enable(unsigned int pin, unsigned int freq, float duty) {

  int resolution = 8;

  if (duty > 1.0f)       duty = 1.0f;

  pinMode(pin,OUTPUT);
  ledcWriteTone(pin, 0); //disable ledc at pin.

  if (freq) {
    if (ledcAttach(pin, freq, resolution) == 0)
      return -1;
    ledcWriteTone(pin, freq);
    ledcWrite(pin, (unsigned int)(duty * ((1 << resolution) - 1)));
  }

  return 0;
}

Debug Message

E (93107) ledc: requested frequency and duty resolution can not be achieved, try                                                                                                              reducing freq_hz or duty_resolution. div_param=0
[ 92088][E][esp32-hal-ledc.c:262] ledcWriteTone(): ledcWriteTone configuration f                                                                                                             ailed!

Other Steps to Reproduce

No response

I have checked existing issues, online documentation and the Troubleshooting Guide

• I confirm I have checked existing issues, online documentation and Troubleshooting guide.

[vvb333007]

Full debug message:

[ 82797][I][esp32-hal-ledc.c:166] ledcAttachChannel(): LEDC attached to pin 2 (c hannel 0, resolution 8)
E (83826) ledc: requested frequency and duty resolution can not be achieved, try reducing freq_hz or duty_resolution. div_param=0
[ 82807][E][esp32-hal-ledc.c:262] ledcWriteTone(): ledcWriteTone configuration f ailed!

[lbernstone]

What tone are you trying to generate at 78KHz? Human hearing doesn't get anywhere near that. For general PWM, use ledc.

[vvb333007]

I am using ledc. It is in the title.

[lbernstone]

ledcWriteTone is a convenience function intended for producing audible signals. This is why it is fixed at 10-bit, in order to generate frequencies b/w 3kHz-10kHz.
If you want to generate a PWM signal, use ledcAttach and ledcWrite to get the required frequency. Use a high bit resolution to get the widest range- 12-bit is what you would typically use to drive LEDs or motors at frequencies high enough (>20kHz) that you won't hear the hum.