Remote Control Transceiver (RMT)
What can the RMT peripheral on ESP chips be used for in practical?
For applications of RMT, please refer to RMT application examples. It can be used for infrared remote control, LED strip lighting, D-shot motor control, and so on.
Which ESP chip is recommended for utilizing the RMT functionality?
ESP32-S3 is recommended because it is currently the only chip with RMT DMA support. This ensures RMT is not interfered by interrupts caused by Wi-Fi, Bluetooth, and other peripherals.
How to change the clock to REF_TICK in RMT?
- CHIP: ESP32 | ESP32-S2 | ESP32-C3
By using the rmt_set_source_clk interface.
When ESP32 RMT controls the WS2812 light strip with Wi-Fi or Bluetooth enabled, there are some data frame exceptions. How to solve the issue?
This problem is difficult to solve on non-ESP32-S3 chips, because the RMT lighting up LED (especially when many LEDs) rely heavily on interrupts, and does not support DMA, thus requiring software to switch ping-pong buffer in the interrupt. If the interrupt does not respond in time, there will be a problem. By default (one memory block is set), after lighting up two LEDs, the RMT driver will go into the interrupt to switch the internal ping-pong buffer.
Workaround:
For esp-idf release/v4.4 and earlier versions, increase mem_block_num. There is a change in release/v5.0. Please see Breaking Changes in Usage。
Install the RMT interrupts on a specific CPU core by calling the driver install function in a pin-to-core task, thus avoiding the core used by Wi-Fi or Bluetooth.
You can also use SPI DMA as an alternative to RMT to solve this issue. For more details, please refer to the SPI DMA LED strip example.
If you are in the product selection stage, it is recommended to use ESP32-S3 RMT.
How can I quickly adapt other infrared protocols based on the IR NEC example in ESP-IDF？
You can accelerate the adaptation of other infrared protocols based on the IR NEC example by using the RMT Encoder.
If you need the infrared learning function, you can use the ir_learn component.
ESP32-S3 RMT supports configuring 4 RMT RX/TX channels. Why does it fail when creating more than 2 RMT TX channels in a row using rmt_new_tx_channel?
This is because the mem_block_symbols parameter configured in the tx_chan_config structure is too large. On ESP32-S3, the size of each dedicated memory block for RMT is 48 bytes. If the mem_block_symbols parameter exceeds 48, creating a TX channel will actually occupy the memory block of the next adjacent channel as well. Therefore, if you want to create and use 4 RMT RX/TX channels simultaneously, the mem_block_symbols parameter should not exceed 48.
Please note that the size of each dedicated memory block for RMT on ESP32 is 64 bytes.
Can ESP32-S3 RMT achieve synchronized output for multiple TX channels?
Yes, please refer to the following code snippet:
rmt_channel_handle_t tx_channels[TEST_RMT_CHANS]; rmt_sync_manager_handle_t synchro = NULL; rmt_sync_manager_config_t synchro_config = { .tx_channel_array = tx_channels, .array_size = TEST_RMT_CHANS, }; rmt_new_sync_manager(&synchro_config, &synchro); for (int i = 0; i < TEST_RMT_CHANS; i++) { rmt_transmit(tx_channels[i], led_strip_encoders[i], leds_grb, TEST_LED_NUM * 3, &transmit_config); }
How can I achieve cyclic data transmission using the RMT TX channel on ESP32-S3, such as an infinite loop?
You can realize infinite loop transmission by setting the rmt_transmit_config_t::loop_count to -1. For more details, please refer to Initiate TX Transaction。
Does the ESP32-S3 support One-Wire?
ESP32-S3 can support the One-Wire bus protocol through the RMT peripheral. For specific applications, refer to the “esp-idf/examples/peripherals/rmt/onewire” example.