260 lines
7.4 KiB
C++
260 lines
7.4 KiB
C++
/**
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* @file DShotRMT.cpp
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* @brief DShot signal generation using ESP32 RMT with continuous repeat and pause between frames, including BiDirectional support
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* @author Wastl Kraus
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* @date 2025-06-11
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* @license MIT
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*/
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#include <DShotRMT.h>
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// --- DShotRMT Class ---
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// This class provides an abstraction for sending and optionally receiving DShot frames.
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// It uses ESP32's RMT peripheral for precise timing control, including BiDirectional RX.
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DShotRMT::DShotRMT(gpio_num_t gpio, dshot_mode_t mode, bool isBidirectional)
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: _gpio(gpio), _mode(mode), _isBidirectional(isBidirectional) {}
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// Sets up RMT TX and RX channels as well as encoder configuration
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void DShotRMT::begin()
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{
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// TX RMT Channel Configuration
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_rmt_tx_channel_config = {
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.gpio_num = _gpio,
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.clk_src = DSHOT_CLOCK_SRC_DEFAULT,
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.resolution_hz = DSHOT_RMT_RESOLUTION,
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.mem_block_symbols = 64,
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.trans_queue_depth = 2,
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// .flags = {
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// invert Signal if BiDirectional DShot Mode
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// .invert_out = _isBidirectional,
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// .with_dma = false}
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};
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rmt_new_tx_channel(&_rmt_tx_channel_config, &_rmt_tx_channel);
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rmt_enable(_rmt_tx_channel);
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// RX RMT Channel Configuration (for BiDirectional DShot)
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if (_isBidirectional)
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{
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_rmt_rx_channel_config = {
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.gpio_num = _gpio,
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.clk_src = DSHOT_CLOCK_SRC_DEFAULT,
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.resolution_hz = DSHOT_RMT_RESOLUTION,
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.mem_block_symbols = 64,
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// .flags = {
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// .invert_in = false,
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// .with_dma = false}
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};
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rmt_new_rx_channel(&_rmt_rx_channel_config, &_rmt_rx_channel);
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rmt_enable(_rmt_rx_channel);
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_receive_config.signal_range_min_ns = 300;
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_receive_config.signal_range_max_ns = 5000;
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}
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// Use a copy encoder to send raw symbols
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if (!_dshot_encoder)
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{
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rmt_copy_encoder_config_t enc_cfg = {};
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rmt_new_copy_encoder(&enc_cfg, &_dshot_encoder);
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}
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// Configure transmission looping
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_transmit_config.loop_count = 0;
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_transmit_config.flags.eot_level = _isBidirectional;
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}
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// Encodes and transmits a valid DShot Throttle value (48 - 2047)
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void DShotRMT::setThrottle(uint16_t throttle)
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{
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// Safety first - double check input range and 11 bit "translation"
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throttle = constrain(throttle, DSHOT_THROTTLE_MIN, DSHOT_THROTTLE_MAX) & 0b0000011111111111;
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_lastThrottle = throttle;
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// Convert throttle value to DShot Paket Format
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_tx_packet = assambleDShotPaket(_lastThrottle);
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// Encode RMT symbols
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size_t count = 0;
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encodeDShotTX(_tx_packet, _tx_symbols, count);
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// Send the packet
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rmt_transmit(_rmt_tx_channel, _dshot_encoder, _tx_symbols, count * sizeof(rmt_symbol_word_t), &_transmit_config);
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// Take a break
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esp_rom_delay_us(120);
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}
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// --- Get eRPM from ESC ---
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// Receives and decodes a response frame from ESC containing eRPM info
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uint32_t DShotRMT::getERPM()
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{
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if (_isBidirectional)
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{
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if (_rmt_rx_channel == nullptr)
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return _last_erpm;
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// Attempt to receive a new frame
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if (!rmt_receive(_rmt_rx_channel, _rx_symbols, sizeof(_rx_symbols), &_receive_config))
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return _last_erpm;
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//
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_last_erpm = decodeDShotRX(_rx_symbols, DSHOT_BITS_PER_FRAME);
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return _last_erpm;
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}
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// Nothing to do here
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return _last_erpm;
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}
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// Translate eRPM value to RPM taking magnet count as parameter
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uint32_t DShotRMT::getMotorRPM(uint8_t magnet_count)
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{
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uint8_t pole_count = magnet_count / 2;
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if (pole_count == 0)
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pole_count = 1;
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uint32_t rpm = getERPM() / pole_count;
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return rpm;
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}
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// Calculate CRC for DShot Paket
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uint16_t DShotRMT::calculateCRC(uint16_t dshot_packet)
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{
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uint16_t _packet = (dshot_packet << 1) | (_isBidirectional ? 1 : 0);
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// Clear container before new calculation
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_packet_crc = DSHOT_NULL_PACKET;
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// CRC calculation for DShot (4 bits)
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_packet_crc = ((_packet ^ (_packet >> 4) ^ (_packet >> 8)) & 0b0000000000001111);
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// CRC is inverted for biDirectional DShot
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if (_isBidirectional)
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_packet_crc = (~_packet_crc) & 0b0000000000001111;
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return _packet_crc;
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}
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// Assamble DShot Paket (11 bit throttle + 1 bit telemetry request + 4 bit crc)
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uint16_t DShotRMT::assambleDShotPaket(uint16_t value)
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{
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// Dummy conversion to 11 bits
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uint16_t _value = value & 0b0000011111111111;
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// Clear container
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_tx_packet = DSHOT_NULL_PACKET;
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// Assemble raw DShot packet and add checksum
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_packet_crc = calculateCRC(_value);
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_tx_packet = (_value << 1) | (_isBidirectional ? 1 : 0);
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_tx_packet = (_tx_packet << 4) | _packet_crc;
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return _tx_packet;
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}
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// --- Encode DShot TX Frame ---
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// Converts a 16-bit packet into a valid DShot Frame for RMT
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void DShotRMT::encodeDShotTX(uint16_t dshot_packet, rmt_symbol_word_t *symbols, size_t &count)
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{
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// Always start encoding from the top
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count = 0;
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uint32_t ticks_per_bit = 0;
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uint32_t ticks_zero_high = 0;
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uint32_t ticks_one_high = 0;
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switch (_mode)
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{
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case DSHOT150:
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ticks_per_bit = 64;
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ticks_zero_high = 24;
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ticks_one_high = 48;
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break;
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case DSHOT300:
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ticks_per_bit = 32;
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ticks_zero_high = 12;
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ticks_one_high = 24;
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break;
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case DSHOT600:
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ticks_per_bit = 16;
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ticks_zero_high = 6;
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ticks_one_high = 12;
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break;
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case DSHOT1200:
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ticks_per_bit = 8;
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ticks_zero_high = 3;
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ticks_one_high = 6;
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break;
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case DSHOT_OFF:
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default:
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ticks_per_bit = 0;
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ticks_zero_high = 0;
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ticks_one_high = 0;
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break;
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}
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uint32_t ticks_zero_low = ticks_per_bit - ticks_zero_high;
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uint32_t ticks_one_low = ticks_per_bit - ticks_one_high;
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// Fill the 16 DShot-Bits Array with selected timings
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for (int i = 15; i >= 0; i--)
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{
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bool bit = (dshot_packet >> i) & 0x01;
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if (_isBidirectional)
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{
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symbols[count].level0 = 0;
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symbols[count].duration0 = bit ? ticks_one_high : ticks_zero_high;
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symbols[count].level1 = 1;
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symbols[count].duration1 = bit ? ticks_one_low : ticks_zero_low;
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}
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else
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{
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symbols[count].level0 = 1;
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symbols[count].duration0 = bit ? ticks_one_high : ticks_zero_high;
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symbols[count].level1 = 0;
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symbols[count].duration1 = bit ? ticks_one_low : ticks_zero_low;
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}
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count++;
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}
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}
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// Decodes a response frame from ESC containing eRPM info
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uint16_t DShotRMT::decodeDShotRX(const rmt_symbol_word_t *symbols, uint32_t count)
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{
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// Container for received frame
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uint16_t _rec_frame = DSHOT_NULL_PACKET;
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// Fill the Frame bit by bit
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for (size_t i = 0; i < DSHOT_BITS_PER_FRAME && i < count; ++i)
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{
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bool bit = (symbols[i].duration0 < symbols[i].duration1);
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_rec_frame = (_rec_frame << 1) | bit;
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}
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// Store the received CRC for checking
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uint16_t _temp = _rec_frame >> 4;
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// Masking the received CRC
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uint8_t crc_recv = _rec_frame & 0x0F;
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// Calculate CRC for received frame again
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uint8_t crc_calc = (_temp ^ (_temp >> 4) ^ (_temp >> 8)) & 0b0000000000001111;
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if (_isBidirectional)
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crc_calc = (~crc_calc) & 0x0F;
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// Checking CRC
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if (crc_recv != crc_calc)
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return _last_erpm;
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// Cut "telemetric" bit leaving "raw" value
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uint16_t raw = _temp >> 1;
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return _last_erpm = raw;
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}
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