DShotRMT/README.md

 [![Arduino CI](https://github.com/derdoktor667/DShotRMT/actions/workflows/esp32.yml/badge.svg?event=push)](https://github.com/derdoktor667/DShotRMT/actions/workflows/esp32.yml)

## DShot ESP32 Library utilizing RMT

### The DShot Protocol
The DSHOT protocol consists of transmitting 16-bit packets to the ESCs: 11-bit throttle value,  1-bit to request telemetry and a 4-bit checksum. There are three major protocol speeds: DSHOT150, DSHOT300 and DSHOT600.

| DSHOT | Bitrate   | TH1   | TH0    | Bit Time µs | Frame Time µs |
|-------|------------|-------|--------|------------|---------------|
| 150   | 150kbit/s  | 5.00  | 2.50   | 6.67       | 106.72        |
| 300   | 300kbit/s  | 2.50  | 1.25   | 3.33       | 53.28         |
| 600   | 600kbit/s  | 1.25  | 0.625  | 1.67       | 26.72         |
| 1200  | 1200kbit/s | 0.625 | 0.313  | 0.83       | 13.28         |

#### Calculating the CRC
The checksum is calculated over the throttle value and the telemetry bit, so the “first” 12 bits our value in the following example:

    crc = (value ^ (value >> 4) ^ (value >> 8)) & 0x0F;

### Bidirectional DSHOT
Bidirectional DSHOT is also known as inverted DSHOT, because the signal level is inverted, so 1 is low and a 0 is high. This is done in order to let the ESC know, that we are operating in bidirectional mode and that it should be sending back eRPM telemetry packages.

#### Calculating the Bidirectional CRC
The calculation of the checksum is basically the same, just before the last step the values are inverted:

    crc = (~(value ^ (value >> 4) ^ (value >> 8))) & 0x0F;

### Using RMT on ESP32
The RMT (Remote Control) is a peripheral designed to generate accurate and stable signals to control external devices such as LEDs, motors, and other peripherals. It is well suited for generating the DShot signals in a high-performance and accurate way on the ESP32 platform.

#### Advantages of using RMT
- Generates accurate signals
- Supports programmable timing
- Configurable number of channels

#### DShot RMT Library for ESP32
The DShot RMT Library for ESP32 provides a convenient way of generating DShot signals using the RMT peripheral on the ESP32 platform. The library supports all three major DShot speeds: DSHOT150, DSHOT300, and DSHOT600.

#### References
- [DSHOT - the missing Handbook](https://brushlesswhoop.com/dshot-and-bidirectional-dshot/)
- [DSHOT in the Dark](https://dmrlawson.co.uk/index.php/2017/12/04/dshot-in-the-dark/)
- [ESP32 Technical Reference Manual](https://www.espressif.com/sites/default/files/documentation/esp32_technical_reference_manual_en.pdf)