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benpeoples/readme.txt

Created June 1, 2020 16:03
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ESP32 LEDC Maximum frequency by resolution
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readme.txt
Per this forum post: https://esp32.com/viewtopic.php?t=6701
The way to calculate max PWM frequency is integer (log 2 (LEDC_APB_CLK / frequency))
With a LEDC_APB_CLK == 80MHz, these are the following maximum values, in Hz:
LEDC_TIMER_1_BIT, 40000000
LEDC_TIMER_2_BIT, 20000000
LEDC_TIMER_3_BIT, 10000000
LEDC_TIMER_4_BIT, 5000000
LEDC_TIMER_5_BIT, 2500000
LEDC_TIMER_6_BIT, 1250000
LEDC_TIMER_7_BIT, 625000
LEDC_TIMER_8_BIT, 312500
LEDC_TIMER_9_BIT, 156250
LEDC_TIMER_10_BIT, 78125
LEDC_TIMER_11_BIT, 39062
LEDC_TIMER_12_BIT, 19531
LEDC_TIMER_13_BIT, 9765
LEDC_TIMER_14_BIT, 4882
LEDC_TIMER_15_BIT, 2441
LEDC_TIMER_16_BIT, 1220
LEDC_TIMER_17_BIT, 610
LEDC_TIMER_18_BIT, 305
LEDC_TIMER_19_BIT, 152
LEDC_TIMER_20_BIT, 76
@alayshoo
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alayshoo commented Jun 23, 2025 •
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Hi,

Frustrated with setting random values on ledcAttach for an ESP32-S3 and the ledcAttach failing so I went looking and found this on a forum.

Still, trying these values didn't lead me anywhere so I tried a small routine to check the maximums on the ESP32-S3. My values seemed to be about half of these and in some Espressiff docs or datasheets I found a reference to the base clock being 40MHz for the ESP32-S3. This would indicate that one just needs to shift one value to find the right maximum (8bit max of the OG ESP32 would be the 7 bit max of the S3).

I might be wrong on this but leaving this bit of information here just in case someone with an S3 finds it useful.

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