43 lines
2.5 KiB
Markdown
43 lines
2.5 KiB
Markdown
[](https://github.com/derdoktor667/DShotRMT/actions/workflows/esp32.yml)
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## DShot ESP32 Library utilizing RMT
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### The DShot Protocol
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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.
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| DSHOT | Bitrate | TH1 | TH0 | Bit Time µs | Frame Time µs |
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|-------|------------|-------|--------|------------|---------------|
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| 150 | 150kbit/s | 5.00 | 2.50 | 6.67 | 106.72 |
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| 300 | 300kbit/s | 2.50 | 1.25 | 3.33 | 53.28 |
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| 600 | 600kbit/s | 1.25 | 0.625 | 1.67 | 26.72 |
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| 1200 | 1200kbit/s | 0.625 | 0.313 | 0.83 | 13.28 |
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#### Calculating the CRC
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The checksum is calculated over the throttle value and the telemetry bit, so the “first” 12 bits our value in the following example:
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crc = (value ^ (value >> 4) ^ (value >> 8)) & 0x0F;
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### Bidirectional DSHOT
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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.
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#### Calculating the Bidirectional CRC
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The calculation of the checksum is basically the same, just before the last step the values are inverted:
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crc = (~(value ^ (value >> 4) ^ (value >> 8))) & 0x0F;
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### Using RMT on ESP32
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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.
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#### Advantages of using RMT
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- Generates accurate signals
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- Supports programmable timing
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- Configurable number of channels
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#### DShot RMT Library for ESP32
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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.
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#### References
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- [DSHOT - the missing Handbook](https://brushlesswhoop.com/dshot-and-bidirectional-dshot/)
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- [DSHOT in the Dark](https://dmrlawson.co.uk/index.php/2017/12/04/dshot-in-the-dark/)
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- [ESP32 Technical Reference Manual](https://www.espressif.com/sites/default/files/documentation/esp32_technical_reference_manual_en.pdf)
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