Please help me understand this code

horace · May 18, 2025, 8:32am

replaced signal generator with ESP32S3 using the RMT to generate the test signals

// ESP32S3 RMT two signals synchroinized
//  1. square wave 100KHz, 1MHz, etc on GPIO 15
//  2. 100uSec pulse every second on GPIO 14

// https://docs.espressif.com/projects/esp-idf/en/v5.3.1/esp32/api-reference/peripherals/rmt.html

// on a ESP32 displays error
//  rmt_new_sync_manager(345): sync manager not supported

#include "Arduino.h"
#include "driver/rmt_tx.h"

void setup() {
  Serial.begin(115200);
  delay(2000);
  Serial.println("ESP32S3 RMT two signals synchroinized");
  Serial.println(" 1. square wave 100KHz, 1MHz, etc on GPIO 15");
  Serial.println(" 2. 100uSec pulse every second on GPIO 14");

  delay(2000);
  // setup two Tx channels
  rmt_channel_handle_t tx_channels[2] = { NULL };
  gpio_num_t tx_gpio_number[2] = { GPIO_NUM_15, GPIO_NUM_14 };  // pin numbers
  rmt_tx_channel_config_t tx_chan_config_1 = {
    .gpio_num = tx_gpio_number[0],
    .clk_src = RMT_CLK_SRC_DEFAULT,
    .resolution_hz = 20 * 1000 * 1000,  // 20MHz clock
    .mem_block_symbols = 64,
    .trans_queue_depth = 1,
  };
  ESP_ERROR_CHECK(rmt_new_tx_channel(&tx_chan_config_1, &tx_channels[0]));
  rmt_tx_channel_config_t tx_chan_config_2 = {
    .gpio_num = tx_gpio_number[1],
    .clk_src = RMT_CLK_SRC_DEFAULT,
    .resolution_hz = 1000000,  // 1MHz clock
    .mem_block_symbols = 64,
    .trans_queue_depth = 1,
  };
  ESP_ERROR_CHECK(rmt_new_tx_channel(&tx_chan_config_2, &tx_channels[1]));
  rmt_transmit_config_t transmitConfig = {
    .loop_count = -1
  };
  rmt_encoder_handle_t copyEncoder{ NULL };
  rmt_copy_encoder_config_t copyEncoderConfig = {};
  assert(rmt_new_copy_encoder(&copyEncoderConfig, &copyEncoder) == ESP_OK && "Failed to Create Copy Encoder");
  ESP_ERROR_CHECK(rmt_enable(tx_channels[1]));
  ESP_ERROR_CHECK(rmt_enable(tx_channels[0]));

  // setup sync manage for the two pulses
  rmt_sync_manager_handle_t synchro = NULL;
  rmt_sync_manager_config_t synchro_config = {
    .tx_channel_array = tx_channels,
    .array_size = sizeof(tx_channels) / sizeof(tx_channels[0]),
  };
  ESP_ERROR_CHECK(rmt_new_sync_manager(&synchro_config, &synchro));

  Serial.println("Starting Transmitters");
  // 100KHz square wave - clock is 20MHz
  const rmt_symbol_word_t pulsePattern1[] = {
    { .duration0 = 100, .level0 = 1, .duration1 = 100, .level1 = 0 },  };
  // 100uSec pulse every second - clock is 1mHz
  const rmt_symbol_word_t pulsePattern2[] = {
  // 100uSec pluse
  {50,1,50,1,},
  // total 1 second period
  {24950,0,24950,0,}, // note using 15bit counters - see Layout of RMT Symbols
  {25000,0,25000,0,},
  {25000,0,25000,0,},
  {25000,0,25000,0,},
  {25000,0,25000,0,},
  {25000,0,25000,0,},
  {25000,0,25000,0,},
  {25000,0,25000,0,},
  {25000,0,25000,0,},
  {25000,0,25000,0,},
  {25000,0,25000,0,},
  {25000,0,25000,0,},
  {25000,0,25000,0,},
  {25000,0,25000,0,},
  {25000,0,25000,0,},
  {25000,0,25000,0,},
  {25000,0,25000,0,},
  {25000,0,25000,0,},
  {25000,0,25000,0,},
  {25000,0,25000,0,},
    // Looping mode needs a Zero ending data to mark the EOF
  { 0, 0, 0, 0 }
};
  assert(rmt_transmit(tx_channels[0], copyEncoder, &pulsePattern1, sizeof(pulsePattern1), &transmitConfig) == ESP_OK && "Failed to begin transmitting");
  assert(rmt_transmit(tx_channels[1], copyEncoder, &pulsePattern2, sizeof(pulsePattern2), &transmitConfig) == ESP_OK && "Failed to begin transmitting");
  Serial.println("Transmitters Running");
}
void loop() {
}

e.g. 100KHz signal

serial output of test runs counting pulses up to 4MHz

GPIO 4 100KHz

test Pulse count: 10 frequency 100000Hz
period 999991uSec width = 98uSec  frequency 1.00Hz
test Pulse count: 10 frequency 100000Hz
period 999990uSec width = 99uSec  frequency 1.00Hz
test Pulse count: 10 frequency 100000Hz
period 999991uSec width = 99uSec  frequency 1.00Hz
test Pulse count: 10 frequency 100000Hz
period 999991uSec width = 99uSec  frequency 1.00Hz
test Pulse count: 10 frequency 100000Hz
period 999991uSec width = 99uSec  frequency 1.00Hz
test Pulse count: 10 frequency 100000Hz
period 999991uSec width = 99uSec  frequency 1.00Hz
test Pulse count: 10 frequency 100000Hz
period 999991uSec width = 99uSec  frequency 1.00Hz
test Pulse count: 10 frequency 100000Hz
period 999991uSec width = 99uSec  frequency 1.00Hz
test Pulse count: 10 frequency 100000Hz
period 999991uSec width = 99uSec  frequency 1.00Hz
test Pulse count: 10 frequency 100000Hz

----------------------------------------------------
GPIO 4 1MHz signal

test Pulse count: 100 frequency 1000000Hz
period 999991uSec width = 99uSec  frequency 1.00Hz
test Pulse count: 100 frequency 1000000Hz
period 999992uSec width = 99uSec  frequency 1.00Hz
test Pulse count: 100 frequency 1000000Hz
period 999991uSec width = 99uSec  frequency 1.00Hz
test Pulse count: 100 frequency 1000000Hz
period 999992uSec width = 99uSec  frequency 1.00Hz
test Pulse count: 100 frequency 1000000Hz
period 999991uSec width = 99uSec  frequency 1.00Hz
test Pulse count: 100 frequency 1000000Hz
period 999992uSec width = 98uSec  frequency 1.00Hz
test Pulse count: 100 frequency 1000000Hz
period 999992uSec width = 98uSec  frequency 1.00Hz
test Pulse count: 100 frequency 1000000Hz
period 999991uSec width = 99uSec  frequency 1.00Hz
test Pulse count: 100 frequency 1000000Hz
period 999992uSec width = 99uSec  frequency 1.00Hz
test Pulse count: 100 frequency 1000000Hz
period 999991uSec width = 99uSec  frequency 1.00Hz
test Pulse count: 100 frequency 1000000Hz
period 999992uSec width = 98uSec  frequency 1.00Hz
test Pulse count: 100 frequency 1000000Hz
period 999991uSec width = 99uSec  frequency 1.00Hz
test Pulse count: 100 frequency 1000000Hz

----------------------------------------------------------------

2MHz

period 999991uSec width = 99uSec  frequency 1.00Hz
test Pulse count: 200 frequency 2000000Hz
period 999992uSec width = 98uSec  frequency 1.00Hz
test Pulse count: 200 frequency 2000000Hz
period 999991uSec width = 99uSec  frequency 1.00Hz
test Pulse count: 200 frequency 2000000Hz
period 999991uSec width = 99uSec  frequency 1.00Hz
test Pulse count: 200 frequency 2000000Hz
period 999991uSec width = 99uSec  frequency 1.00Hz
test Pulse count: 200 frequency 2000000Hz
period 999991uSec width = 99uSec  frequency 1.00Hz
test Pulse count: 200 frequency 2000000Hz
period 999992uSec width = 98uSec  frequency 1.00Hz
test Pulse count: 200 frequency 2000000Hz
period 999991uSec width = 99uSec  frequency 1.00Hz
test Pulse count: 200 frequency 2000000Hz
period 999991uSec width = 99uSec  frequency 1.00Hz
test Pulse count: 200 frequency 2000000Hz
period 999991uSec width = 99uSec  frequency 1.00Hz
test Pulse count: 200 frequency 2000000Hz
period 999991uSec width = 99uSec  frequency 1.00Hz
test Pulse count: 200 frequency 2000000Hz
period 999992uSec width = 98uSec  frequency 1.00Hz
test Pulse count: 200 frequency 2000000Hz
period 999991uSec width = 99uSec  frequency 1.00Hz
test Pulse count: 200 frequency 2000000Hz
period 999991uSec width = 99uSec  frequency 1.00Hz
test Pulse count: 200 frequency 2000000Hz
period 999991uSec width = 99uSec  frequency 1.00Hz

------------------------------------------------------------

4MHz

test Pulse count: 4 frequency 40000Hz
period 534287uSec width = 8090521uSec  frequency 1.87Hz
test Pulse count: 1 frequency 10000Hz
period 534287uSec width = 10990883uSec  frequency 1.87Hz
test Pulse count: 400 frequency 4000000Hz
period 10991020uSec width = 99uSec  frequency 0.09Hz
test Pulse count: 400 frequency 4000000Hz
period 999992uSec width = 98uSec  frequency 1.00Hz
test Pulse count: 400 frequency 4000000Hz
period 999990uSec width = 99uSec  frequency 1.00Hz
test Pulse count: 400 frequency 4000000Hz
period 999991uSec width = 99uSec  frequency 1.00Hz
test Pulse count: 400 frequency 4000000Hz
period 999991uSec width = 99uSec  frequency 1.00Hz
test Pulse count: 400 frequency 4000000Hz
period 999991uSec width = 99uSec  frequency 1.00Hz
test Pulse count: 400 frequency 4000000Hz
period 999991uSec width = 99uSec  frequency 1.00Hz
test Pulse count: 400 frequency 4000000Hz
period 999991uSec width = 99uSec  frequency 1.00Hz
test Pulse count: 400 frequency 4000000Hz
period 999991uSec width = 99uSec  frequency 1.00Hz
test Pulse count: 400 frequency 4000000Hz
period 999991uSec width = 99uSec  frequency 1.00Hz
test Pulse count: 400 frequency 4000000Hz
period 999991uSec width = 99uSec  frequency 1.00Hz

Topic		Replies	Views
Best chip for frequency/pulse counting? Sensors	15	7831	May 6, 2021
Fast Pulse Counter - High Speed Counter Programming	9	15399	May 5, 2021
Frequency Counter Library Development	81	38879	May 6, 2021
Reading Pulses with Interrupts - Advices. Programming	28	7476	May 5, 2021
counting pulses without using interrupt General Guidance	54	12693	May 5, 2021

Please help me understand this code

Related topics