Uli Köhler

On the ESP32 platform, you can use the LEDC PWM driver to generate programmable dead time by setting the duty (i.e. length of pulse) and hpoint(time offset of pulse) appropriately.

#include <driver/ledc.h>

ledc_timer_config_t ledc_timer = {
    .speed_mode       = LEDC_LOW_SPEED_MODE,
    .duty_resolution  = LEDC_TIMER_8_BIT,
    .timer_num        = LEDC_TIMER_0,
    .freq_hz          = 100000,
    .clk_cfg          = LEDC_AUTO_CLK
};
ESP_ERROR_CHECK(ledc_timer_config(&ledc_timer));

uint32_t deadTime = 20; // Large value to show clearly on the oscilloscope

ledc_channel_config_t ledc_noninverted_channel = {
    .gpio_num       = GPIO_NUM_10,
    .speed_mode     = LEDC_LOW_SPEED_MODE,
    .channel        = LEDC_CHANNEL_0,
    .intr_type      = LEDC_INTR_DISABLE,
    .timer_sel      = LEDC_TIMER_0,
    .duty           = 127-deadTime/2, // Set duty to 50%
    .hpoint         = 0
};
ESP_ERROR_CHECK(ledc_channel_config(&ledc_noninverted_channel));

ledc_channel_config_t ledc_complementary_channel = {
    .gpio_num       = GPIO_NUM_11,
    .speed_mode     = LEDC_LOW_SPEED_MODE,
    .channel        = LEDC_CHANNEL_1,
    .intr_type      = LEDC_INTR_DISABLE,
    .timer_sel      = LEDC_TIMER_0,
    .duty           = 127-deadTime/2, // Set cycle to start just after 50%
    .hpoint         = 127,
};
ESP_ERROR_CHECK(ledc_channel_config(&ledc_complementary_channel));

#include <driver/ledc.h>

ledc_timer_config_t ledc_timer = {
    .speed_mode       = LEDC_LOW_SPEED_MODE,
    .duty_resolution  = LEDC_TIMER_8_BIT,
    .timer_num        = LEDC_TIMER_0,
    .freq_hz          = 100000,
    .clk_cfg          = LEDC_AUTO_CLK
};
ESP_ERROR_CHECK(ledc_timer_config(&ledc_timer));

ledc_channel_config_t ledc_inverted_channel = {
    .gpio_num       = GPIO_NUM_11,
    .speed_mode     = LEDC_LOW_SPEED_MODE,
    .channel        = LEDC_CHANNEL_1,
    .intr_type      = LEDC_INTR_DISABLE,
    .timer_sel      = LEDC_TIMER_0,
    .duty           = 128, // Set cycle to start just after 50%
    .hpoint         = 0,
    .flags = {.output_invert = true}
};
ESP_ERROR_CHECK(ledc_channel_config(&ledc_inverted_channel));

#include <driver/ledc.h>

ledc_timer_config_t ledc_timer = {
    .speed_mode       = LEDC_LOW_SPEED_MODE,
    .duty_resolution  = LEDC_TIMER_8_BIT,
    .timer_num        = LEDC_TIMER_0,
    .freq_hz          = 100000,
    .clk_cfg          = LEDC_AUTO_CLK
};
ESP_ERROR_CHECK(ledc_timer_config(&ledc_timer));

ledc_channel_config_t ledc_noninverted_channel = {
    .gpio_num       = GPIO_NUM_10,
    .speed_mode     = LEDC_LOW_SPEED_MODE,
    .channel        = LEDC_CHANNEL_0,
    .intr_type      = LEDC_INTR_DISABLE,
    .timer_sel      = LEDC_TIMER_0,
    .duty           = 127, // Set duty to 50%
    .hpoint         = 0
};
ESP_ERROR_CHECK(ledc_channel_config(&ledc_noninverted_channel));

ledc_channel_config_t ledc_inverted_channel = {
    .gpio_num       = GPIO_NUM_11,
    .speed_mode     = LEDC_LOW_SPEED_MODE,
    .channel        = LEDC_CHANNEL_1,
    .intr_type      = LEDC_INTR_DISABLE,
    .timer_sel      = LEDC_TIMER_0,
    .duty           = 128, // Set cycle to start just after 50%
    .hpoint         = 0,
    .flags = {.output_invert = true}
};
ESP_ERROR_CHECK(ledc_channel_config(&ledc_inverted_channel));

In contrast to our previous example from  ESP32 RMT pulse generation minimal example using Arduino & PlatformIO this example uses the new rmt_tx API.

#include <driver/rmt_tx.h>

rmt_channel_handle_t channel;
rmt_tx_channel_config_t tx_chan_config = {
    .gpio_num = GPIO_NUM_19,          // GPIO number
    .clk_src = RMT_CLK_SRC_DEFAULT,   // select source clock
    .resolution_hz = 1 * 1000 * 1000, // 1 MHz resolution
    .mem_block_symbols = 64,          // memory block size, 64 * 4 = 256 Bytes
    .trans_queue_depth = 1,           // set the number of transactions that can pend in the background
};
ESP_ERROR_CHECK(rmt_new_tx_channel(&tx_chan_config, &channel));
ESP_ERROR_CHECK(rmt_enable(channel));

rmt_symbol_word_t txdata[64];
txdata[0] = {
    .duration0 = 100,
    .level0 = 1,
    .duration1 = 0,
    .level1 = 0,
};

// Create simple encoder
rmt_copy_encoder_config_t encoder_config;
rmt_encoder_handle_t encoder;
ESP_ERROR_CHECK(rmt_new_copy_encoder(&encoder_config, &encoder));

rmt_transmit_config_t tx_config = {
    .loop_count = 0, // no transfer loop
};

while(true)
{
    ESP_ERROR_CHECK(rmt_transmit(channel, encoder, pulseRMT, 1*sizeof(rmt_symbol_word_t), &tx_config));
    // Wait for one second
    vTaskDelay(10 / portTICK_PERIOD_MS);
}

Result: