ESP32S2 (S2FN4R2) and LEDC

[stef-ladefense]

Hi there
I have a few questions, remarks

1. what is the minimum frequency of LEDC?
2. what are the GPIOs of the S2 that support LEDC?

I work on 4 bits (so from 0 to 15), and the minimum frequency is 2500Hz, below that it doesn't work.
on the other hand in 8-bit mode, 1000Hz works well.
in the S2FN4R2 datasheet, it says PWM on all GPIOs, but it doesn't wo,rk on GPIO14, GPIO10.
work well 1, 6 ,8, dont have test other gpio for moment

merci

[VojtechBartoska]

@P-R-O-C-H-Y Can you help answering this?

[P-R-O-C-H-Y]

Hi @stef-ladefense,

1. Minimum frequency is 1Hz. You need to be careful what frequency and duty resolution you select. See ESP-IDF LEDC docs for more info -> link. There is a simple rule for setting LEDC frequency:
   lower frequencies -> higher resolution
   higher frequencies -> lower resolution (example 40MHz freq can be set only with bit resolution 1)
   I was able to set 1Hz frequency using 12 bits resolution ledcSetup(0,1,12);

2. LEDC should work on all available pins, if they are not used for anything else or "reserved" for something. I can test GPIO 10 / 14 to check it.

[stef-ladefense]

hi @P-R-O-C-H-Y
I tested the frequencies on an S2, just to realize the limits.
besides, it is useless to go too low otherwise it flashes.
for the pins, I have not tested further, but the limits that I have found are on an assembly with a screen driven in SPI.

//  Test on Lolin S2 Mini ESP32-S2FN4R2 on gpio15 (internal led) https://www.wemos.cc/en/latest/s2/s2_mini.html
//  bits freq min freq max (Hz)
//  1    19532    ?
//  2    9766     10019569
//  3    4883     5009784
//  4    2442     2504892
//  5    1221     1252446
//  6    611      626223
//  7    306      313111
//  8    153      156555
//  9    77       78277
//  10   39       39138
//  11   20       19569
//  12   10       9784
//  13   5        4892
//  14   3        2446

#define bit_num 3
#define freq 5000
#define channel 0
#define pin 15
const uint16_t maxi = (1 << bit_num) - 1;
uint16_t dutyCycle = 0;
int8_t _direction = 1;

void setup() {
  ledcSetup(channel, freq, bit_num);
  ledcAttachPin(pin, channel);
}

void loop() {
  if (dutyCycle == maxi) _direction = -1;
  else if (dutyCycle == 0) _direction = 1;
  
  dutyCycle += _direction;
  ledcWrite(channel, dutyCycle);
  delay(5);
}