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ESP32 LEDC PWM Guide: Channels, Frequency vs Resolution Trade-off
The ESP32 LEDC offers 16 PWM channels. Frequency and resolution trade off against each other — here is the maths and recommended values.
Channel count
The original ESP32's LEDC provides 16 PWM channels (8 high-speed + 8 low-speed) across four timer groups. Channels in the same group share frequency and resolution; groups are independent. That constraint catches a lot of people out.
Frequency vs resolution
The core formula:
actual frequency = 80 MHz / ( divider × 2 ^ resolution_bits )
So higher frequency means lower resolution. With the divider at 1, the theoretical ceilings are:
| Resolution | Duty steps | Max frequency | Good for |
|---|---|---|---|
| 8-bit | 256 | 312.5 kHz | Switching supplies, fast dimming |
| 10-bit | 1024 | 78.1 kHz | Flicker-free LED dimming |
| 12-bit | 4096 | 19.5 kHz | Servos, fine dimming |
| 13-bit | 8192 | 9.8 kHz | Motor drives |
| 20-bit | 1,048,576 | 76.3 Hz | Very slow, very fine control |
Need low frequency and high resolution? Increase the divider. A 50 Hz servo with a large divider and 12-bit resolution is perfectly fine — you do not have to drop to 8 bits.
Recommended settings
- LED dimming: 10–12 bit at ≥ 1 kHz. Below a few hundred Hz the flicker is visible, especially through a phone camera.
- Servos: 50 Hz (20 ms period), duty mapped to 0.5–2.5 ms pulses, 12-bit or better.
- DC motors: 5–20 kHz to move the whine above the audible range.
- Passive buzzers: change frequency to make tones, around 50% duty.
Notes
- Maximum resolution differs per chip (20 bits on the original, less on some newer parts) — verify against the official documentation.
- Hardware fade is handy, but check whether your call is blocking or non-blocking; you need the fade ISR installed for true background operation.
- LEDC runs through the GPIO matrix, so almost any output pin works — except the input-only GPIO 34–39.
- "Low-speed" channels can keep running from the RTC clock during sleep, which is ideal for a low-power breathing LED.
Data verified：2026-10-20 · Cross-checked against Espressif documentation. Anything that varies between chips or ESP-IDF releases is marked rather than guessed.
Official peripheral docs →
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