RMT

About

Note

This is a work in progress project and this section is still missing. If you want to contribute, please see the Contributions Guide.

Remote Control Transceiver (RMT) peripheral was designed to act as an infrared transceiver.

Example

To get started with RMT, you can try:

RMT Write Neo Pixel

#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "freertos/event_groups.h"
#include "Arduino.h"

#include "esp32-hal.h"

// The effect seen in ESP32C3, ESP32S2 and ESP32S3 is like a Blink of RGB LED
#if CONFIG_IDF_TARGET_ESP32S2
#define BUILTIN_RGBLED_PIN   18
#elif CONFIG_IDF_TARGET_ESP32S3
#define BUILTIN_RGBLED_PIN   48
#elif CONFIG_IDF_TARGET_ESP32C3
#define BUILTIN_RGBLED_PIN   8
#else
#define BUILTIN_RGBLED_PIN   21   // ESP32 has no builtin RGB LED
#endif

#define NR_OF_LEDS   8*4
#define NR_OF_ALL_BITS 24*NR_OF_LEDS

//
// Note: This example uses Neopixel LED board, 32 LEDs chained one
//      after another, each RGB LED has its 24 bit value 
//      for color configuration (8b for each color)
//
//      Bits encoded as pulses as follows:
//
//      "0":
//         +-------+              +--
//         |       |              |
//         |       |              |
//         |       |              |
//      ---|       |--------------|
//         +       +              +
//         | 0.4us |   0.85 0us   |
//
//      "1":
//         +-------------+       +--
//         |             |       |
//         |             |       |
//         |             |       |
//         |             |       |
//      ---+             +-------+
//         |    0.8us    | 0.4us |

rmt_data_t led_data[NR_OF_ALL_BITS];

rmt_obj_t* rmt_send = NULL;

void setup() 
{
    Serial.begin(115200);
    
    if ((rmt_send = rmtInit(BUILTIN_RGBLED_PIN, RMT_TX_MODE, RMT_MEM_64)) == NULL)
    {
        Serial.println("init sender failed\n");
    }

    float realTick = rmtSetTick(rmt_send, 100);
    Serial.printf("real tick set to: %fns\n", realTick);

}

int color[] =  { 0x55, 0x11, 0x77 };  // RGB value
int led_index = 0;

void loop() 
{
    // Init data with only one led ON
    int led, col, bit;
    int i=0;
    for (led=0; led<NR_OF_LEDS; led++) {
        for (col=0; col<3; col++ ) {
            for (bit=0; bit<8; bit++){
                if ( (color[col] & (1<<(7-bit))) && (led == led_index) ) {
                    led_data[i].level0 = 1;
                    led_data[i].duration0 = 8;
                    led_data[i].level1 = 0;
                    led_data[i].duration1 = 4;
                } else {
                    led_data[i].level0 = 1;
                    led_data[i].duration0 = 4;
                    led_data[i].level1 = 0;
                    led_data[i].duration1 = 8;
                }
                i++;
            }
        }
    }
    // make the led travel in the pannel
    if ((++led_index)>=NR_OF_LEDS) {
        led_index = 0;
    }

    // Send the data
    rmtWrite(rmt_send, led_data, NR_OF_ALL_BITS);

    delay(100);
}

Complete list of RMT examples.