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DShotRMT/DShotRMT.h

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/**
* @file DShotRMT.h
* @brief DShot signal generation using ESP32 RMT with bidirectional support
* @author Wastl Kraus
* @date 2025-06-11
* @license MIT
*/
#pragma once
#include <Arduino.h>
#include <dshot_commands.h>
#include <driver/gpio.h>
#include <driver/rmt_tx.h>
#include <driver/rmt_rx.h>
// DShot Protocol Constants
static constexpr auto DSHOT_THROTTLE_FAILSAFE = 0;
static constexpr auto DSHOT_THROTTLE_MIN = 48;
static constexpr auto DSHOT_THROTTLE_MAX = 2047;
static constexpr auto DSHOT_BITS_PER_FRAME = 16;
static constexpr auto DSHOT_SWITCH_TIME = 30; // Additional time in us for bidir switching
static constexpr auto DSHOT_NULL_PACKET = 0b0000000000000000;
static constexpr auto DSHOT_RX_TIMEOUT_MS = 2; // Never reached, just a timeeout
static constexpr auto GCR_BITS_PER_FRAME = 21; // Number of GCR bits in a DShot answer frame (1 start + 16 data + 4 CRC)
static constexpr auto DEFAULT_MOTOR_MAGNET_COUNT = 14;
static constexpr auto MAGNETS_PER_POLE_PAIR = 2;
static constexpr auto MIN_POLE_PAIRS = 1;
static constexpr auto NO_DSHOT_ERPM = 0;
static constexpr auto NO_DSHOT_RPM = 0;
// RMT Configuration Constants
constexpr auto DSHOT_CLOCK_SRC_DEFAULT = RMT_CLK_SRC_DEFAULT;
constexpr auto DSHOT_RMT_RESOLUTION = 10 * 1000 * 1000; // 10 MHz resolution
constexpr auto RMT_BUFFER_SIZE = DSHOT_BITS_PER_FRAME;
constexpr auto RMT_BUFFER_SYMBOLS = 64;
constexpr auto RMT_QUEUE_DEPTH = 1;
// Smallest pulse for DShot1200 is 2us. Largest for DShot150 is 40us.
// The range is set from 3us (3000ns) to 60us (60000ns) to be safe across all modes.
constexpr uint32_t DSHOT_PULSE_MIN = 3000;
constexpr uint32_t DSHOT_PULSE_MAX = 60000;
// DShot Modes
typedef enum
{
DSHOT_OFF,
DSHOT150,
DSHOT300,
DSHOT600,
DSHOT1200
} dshot_mode_t;
// DShot Packet
typedef struct
{
uint16_t throttle_value : 11;
bool telemetric_request : 1;
uint16_t checksum : 4;
} dshot_packet_t;
// DShot Timing Configuration
typedef struct
{
uint32_t frame_length_us;
uint16_t ticks_per_bit;
uint16_t ticks_one_high;
uint16_t ticks_one_low;
uint16_t ticks_zero_high;
uint16_t ticks_zero_low;
} dshot_timing_t;
// Error handling
typedef struct
{
bool success;
const char *msg;
} dshot_result_t;
// DShot telemetry result
typedef struct
{
bool success;
uint16_t erpm;
uint16_t motor_rpm;
const char *msg;
} dshot_telemetry_result_t;
// Naming convention
typedef dshotCommands_e dshot_commands_t;
// --- HELPERS ---
void printDShotResult(dshot_result_t &result, Stream &output = Serial);
void printDShotTelemetry(dshot_telemetry_result_t &result, Stream &output = Serial);
//
class DShotRMT
{
public:
// Constructor with GPIO enum
explicit DShotRMT(gpio_num_t gpio = GPIO_NUM_16, dshot_mode_t mode = DSHOT300, bool is_bidirectional = false);
// Constructor with pin number
DShotRMT(uint16_t pin_nr, dshot_mode_t mode, bool is_bidirectional);
// Destructor for "better" code
~DShotRMT();
// Initialize the RMT module and DShot config
dshot_result_t begin();
// Send throttle value (48-2047)
dshot_result_t sendThrottle(uint16_t throttle);
// Send DShot command (0-47)
dshot_result_t sendCommand(uint16_t command);
// --- GETTERS ---
gpio_num_t getGPIO() const { return _gpio; }
uint16_t getDShotPacket() const { return _parsed_packet; }
bool is_bidirectional() const { return _is_bidirectional; }
dshot_mode_t getMode() const { return _mode; }
dshot_telemetry_result_t getTelemetry(uint16_t magnet_count = DEFAULT_MOTOR_MAGNET_COUNT);
// --- INFO ---
void printDShotInfo(Stream &output = Serial) const;
void printCpuInfo(Stream &output = Serial) const;
// --- DEPRECATED METHODS ---
[[deprecated("Use sendThrottle() instead")]]
bool setThrottle(uint16_t throttle)
{
auto result = sendThrottle(throttle);
return result.success;
}
[[deprecated("Use sendCommand() instead")]]
bool sendDShotCommand(uint16_t command)
{
auto result = sendCommand(command);
return result.success;
}
[[deprecated("Use getTelemetry() instead")]]
uint32_t getMotorRPM(uint8_t magnet_count)
{
auto result = getTelemetry(magnet_count);
return result.success;
}
private:
// --- CONFIG ---
gpio_num_t _gpio;
dshot_mode_t _mode;
bool _is_bidirectional;
uint32_t _frame_timer_us;
const dshot_timing_t &_timing_config;
uint16_t _last_throttle;
// --- TIMING & PACKET VARIABLES ---
uint64_t _last_transmission_time;
uint16_t _parsed_packet;
dshot_packet_t _packet;
uint8_t _bitPositions[DSHOT_BITS_PER_FRAME];
uint16_t _level0;
uint16_t _level1;
// --- RMT HARDWARE HANDLES ---
rmt_channel_handle_t _rmt_tx_channel;
rmt_channel_handle_t _rmt_rx_channel;
rmt_encoder_handle_t _dshot_encoder;
// --- RMT CONFIG STRUCTURES ---
rmt_tx_channel_config_t _tx_channel_config;
rmt_rx_channel_config_t _rx_channel_config;
rmt_transmit_config_t _transmit_config;
rmt_receive_config_t _receive_config;
// --- INITS ---
dshot_result_t _initTXChannel();
dshot_result_t _initRXChannel();
dshot_result_t _initDShotEncoder();
// --- PACKET MANAGEMENT ---
dshot_packet_t _buildDShotPacket(const uint16_t value);
uint16_t _parseDShotPacket(const dshot_packet_t &packet);
uint16_t _calculateCRC(const uint16_t data);
void _preCalculateBitPositions();
// --- FRAME PROCESSING ---
dshot_result_t _sendDShotFrame(const dshot_packet_t &packet);
bool IRAM_ATTR _encodeDShotFrame(const dshot_packet_t &packet, rmt_symbol_word_t *symbols);
uint16_t _decodeDShotFrame(const rmt_symbol_word_t *symbols);
// --- TIMING CONTROL ---
bool IRAM_ATTR _timer_signal();
bool _timer_reset();
// -- CALLBACKS ---
rmt_rx_event_callbacks_t _rx_event_callbacks;
volatile rmt_symbol_word_t _rx_symbols_direct[GCR_BITS_PER_FRAME];
volatile uint16_t _last_erpm_atomic;
volatile bool _telemetry_ready_flag;
static bool IRAM_ATTR _rmt_rx_done_callback(rmt_channel_handle_t rmt_rx_channel, const rmt_rx_done_event_data_t *edata, void *user_data);
// --- DSHOT RESULT HANDLER ---
dshot_result_t _result;
// --- DSHOT DEFAULTS ---
static constexpr auto const DSHOT_TELEMETRY_INVALID = (0xffff);
// --- CONSTANTS & ERROR MESSAGES ---
static constexpr bool DSHOT_OK = 0;
static constexpr bool DSHOT_ERROR = 1;
static constexpr char const *NONE = "";
static constexpr char const *UNKNOWN_ERROR = "Unknown Error!";
static constexpr char const *INIT_SUCCESS = "SignalGeneratorRMT initialized successfully";
static constexpr char const *INIT_FAILED = "SignalGeneratorRMT init failed!";
static constexpr char const *TX_INIT_SUCCESS = "TX RMT channel initialized successfully";
static constexpr char const *TX_INIT_FAILED = "TX RMT channel init failed!";
static constexpr char const *RX_INIT_SUCCESS = "RX RMT channel initialized successfully";
static constexpr char const *RX_INIT_FAILED = "RX RMT channel init failed!";
static constexpr char const *RX_BUFFER_FAILED = "RX RMT buffer init failed!";
static constexpr char const *ENCODER_INIT_SUCCESS = "RMT encoder initialized successfully";
static constexpr char const *ENCODER_INIT_FAILED = "RMT encoder init failed!";
static constexpr char const *TRANSMISSION_SUCCESS = "Transmission successfully";
static constexpr char const *TRANSMISSION_FAILED = "Transmission failed!";
static constexpr char const *RECEIVER_FAILED = "RMT receiver failed!";
static constexpr char const *THROTTLE_NOT_IN_RANGE = "Throttle not in range! (48 - 2047)";
static constexpr char const *COMMAND_NOT_VALID = "Command not valid! (0 - 47)";
static constexpr char const *BIDIR_NOT_ENABLED = "Bidirectional DShot not enabled!";
static constexpr char const *TELEMETRY_SUCCESS = "Valid Telemetric Frame received!";
static constexpr char const *TELEMETRY_FAILED = "No valid Telemetric Frame received!";
static constexpr char const *INVALID_MAGNET_COUNT = "Invalid motor magnet count!";
static constexpr char const *TIMING_CORRECTION = "Timing correction!";
};
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