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 RGB LED

// Copyright 2024 Espressif Systems (Shanghai) PTE LTD
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at

//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

/**
 * @brief This example demonstrates usage of RGB LED driven by RMT
 *
 * The output is a visual WS2812 RGB LED color moving in a 8 x 4 LED matrix
 * Parameters can be changed by the user. In a single LED circuit, it will just blink.
 */

// The effect seen in (Espressif devkits) ESP32C6, ESP32H2, ESP32C3, ESP32S2 and ESP32S3 is like a Blink of RGB LED
#ifdef PIN_LED_RGB
#define BUILTIN_RGBLED_PIN PIN_LED_RGB
#else
#define BUILTIN_RGBLED_PIN 21  // ESP32 has no builtin RGB LED (PIN_LED_RGB)
#endif

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

//
// Note: This example uses a board with 32 WS2812b 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];

void setup() {
  Serial.begin(115200);
  if (!rmtInit(BUILTIN_RGBLED_PIN, RMT_TX_MODE, RMT_MEM_NUM_BLOCKS_1, 10000000)) {
    Serial.println("init sender failed\n");
  }
  Serial.println("real tick set to: 100ns");
}

int color[] = {0x55, 0x11, 0x77};  // Green Red Blue values
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 panel
  if ((++led_index) >= NR_OF_LEDS) {
    led_index = 0;
  }
  // Send the data and wait until it is done
  rmtWrite(BUILTIN_RGBLED_PIN, led_data, NR_OF_ALL_BITS, RMT_WAIT_FOR_EVER);
  delay(100);
}

Complete list of RMT examples.