ESP8266/ESP32

On the ESP32, you can use heap_caps_print_heap_info() to print information to the serial port about how much memory is free on the heap (plus other details such as the largest free block).

#include <esp_heap_caps.h>

void setup() {
}

void loop() {
  heap_caps_print_heap_info(MALLOC_CAP_8BIT);
}

Example output

Heap summary for capabilities 0x00000004:
  At 0x3ffb8000 len 6688 free 0 allocated 4404 min_free 0
    largest_free_block 0 alloc_blocks 8 free_blocks 0 total_blocks 8
  At 0x3ffb0000 len 25480 free 0 allocated 22204 min_free 0
    largest_free_block 0 alloc_blocks 70 free_blocks 0 total_blocks 70
  At 0x3ffae6e0 len 6192 free 8 allocated 3860 min_free 8
    largest_free_block 0 alloc_blocks 10 free_blocks 1 total_blocks 11
  At 0x3ffb6388 len 7288 free 0 allocated 4524 min_free 0
    largest_free_block 0 alloc_blocks 38 free_blocks 0 total_blocks 38
  At 0x3ffb9a20 len 16648 free 8 allocated 13964 min_free 0
    largest_free_block 0 alloc_blocks 32 free_blocks 1 total_blocks 33
  At 0x3ffcc5d0 len 80432 free 8 allocated 73140 min_free 8
    largest_free_block 0 alloc_blocks 320 free_blocks 1 total_blocks 321
  At 0x3ffe0440 len 15072 free 0 allocated 12260 min_free 0
    largest_free_block 0 alloc_blocks 41 free_blocks 0 total_blocks 41
  At 0x3ffe4350 len 113840 free 18440 allocated 90724 min_free 2560
    largest_free_block 7796 alloc_blocks 157 free_blocks 12 total_blocks 169
  Totals:
    free 18464 allocated 225080 min_free 2576 largest_free_block 7796

The following function will compute the value of a sine wave using micros() as a timebase, with adjustable frequency. It is hardcoded to expect a 12 bit resolution PWM

/**
 * @brief Calculate the PWM duty cycle (assuming 12 bits resolution) of a sine wave of
 * given frequency. micros() is used as a timebase
 * 
 * @param frequency The frequency in Hz
 * @return int the corresponding 12-bit PWM value
 */
int sinePWMValue(float frequency) {
  unsigned long currentMicros = micros(); // get the current time in microseconds

  // calculate the sine wave value for the current time
  int sineValue = 2048 + 2047 * sin(2 * PI * currentMicros / (1000000 / frequency));
  return sineValue;
}

Based on this, we can use the basic code of our previous post ESP32 minimal Arduino PWM output example (PlatformIO) to generate a 1Hz sine wave (represented by a 10kHz PWM):

#include <Arduino.h>
#include <driver/ledc.h>

void setup() {
    Serial.begin(115200);

    ledcSetup(LEDC_CHANNEL_0, 10000 /* Hz */, 12);

    ledcAttachPin(GPIO_NUM_14, LEDC_CHANNEL_0);
    ledcWrite(LEDC_CHANNEL_0, 2048); // 50%
}

/**
 * @brief Calculate the PWM duty cycle (assuming 12 bits resolution) of a sine wave of
 * given frequency. micros() is used as a timebase
 * 
 * @param frequency The frequency in Hz
 * @return int the corresponding 12-bit PWM value
 */
int sinePWMValue(float frequency) {
  unsigned long currentMicros = micros(); // get the current time in microseconds

  // calculate the sine wave value for the current time
  int sineValue = 2048 + 2047 * sin(2 * PI * currentMicros / (1000000 / frequency));
  return sineValue;
}

void loop() {
    // Example of how to change the duty cycle to 25%
    ledcWrite(LEDC_CHANNEL_0, sinePWMValue(1.0));
}

#include <Arduino.h>
#include <driver/ledc.h>

void setup() {
    Serial.begin(115200);

    ledcSetup(LEDC_CHANNEL_0, 10000 /* Hz */, 12);

    ledcAttachPin(GPIO_NUM_14, LEDC_CHANNEL_0);
    ledcWrite(LEDC_CHANNEL_0, 2048); // 50%
}

void loop() {
    // Example of how to change the duty cycle to 25%
    ledcWrite(LEDC_CHANNEL_0, 1024);
}

This example configures the LEDC PWM timer at 10 kHz with 12 bit resolution, outputting a 50% duty cycle PWM on IO14. This code uses the ESP-IDF API directly in order to configure the PWM

#include <Arduino.h>
#include <driver/ledc.h>

void setup() {
    Serial.begin(115200);

    ledc_timer_config_t ledc_timer = {
        .speed_mode       = LEDC_HIGH_SPEED_MODE,
        .duty_resolution  = LEDC_TIMER_12_BIT,
        .timer_num        = LEDC_TIMER_0,
        .freq_hz          = 10000,
        .clk_cfg          = LEDC_AUTO_CLK
    };
    ESP_ERROR_CHECK(ledc_timer_config(&ledc_timer));

    ledc_channel_config_t ledc_channel = {
        .gpio_num       = GPIO_NUM_14,
        .speed_mode     = LEDC_HIGH_SPEED_MODE,
        .channel        = LEDC_CHANNEL_0,
        .intr_type      = LEDC_INTR_DISABLE,
        .timer_sel      = LEDC_TIMER_0,
        .duty           = 2048, // Set duty to 50%
        .hpoint         = 0
    };
    ESP_ERROR_CHECK(ledc_channel_config(&ledc_channel));
}

void loop() {
}