sbus.h

/*
* Brian R Taylor
* brian.taylor@bolderflight.com
*
* Copyright (c) 2022 Bolder Flight Systems Inc
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the “Software”), to
* deal in the Software without restriction, including without limitation the
* rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
* sell copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
* IN THE SOFTWARE.
*/

#ifndef SRC_SBUS_H_
#define SRC_SBUS_H_

#if defined(ARDUINO)
#include <Arduino.h>
#else
#include <cstddef>
#include <cstdint>
#include "core/core.h"
#endif

namespace bfs {

struct SbusData {
  bool lost_frame;
  bool failsafe;
  bool ch17, ch18;
  static constexpr int8_t NUM_CH = 16;
  int16_t ch[NUM_CH];
};

class SbusRx {
 public:
  #if defined(ESP32)
  SbusRx(HardwareSerial *bus, const int8_t rxpin, const int8_t txpin,
         const bool inv) : uart_(bus), inv_(inv), rxpin_(rxpin), txpin_(txpin)
         {}
  SbusRx(HardwareSerial *bus, const int8_t rxpin, const int8_t txpin,
         const bool inv, const bool fast) : uart_(bus), inv_(inv), fast_(fast),
                                            rxpin_(rxpin), txpin_(txpin) {}
  #else
  explicit SbusRx(HardwareSerial *bus) : uart_(bus) {}
  SbusRx(HardwareSerial *bus, const bool inv) : uart_(bus), inv_(inv) {}
  SbusRx(HardwareSerial *bus, const bool inv, const bool fast) : uart_(bus),
                                                                 inv_(inv),
                                                                 fast_(fast) {}
  #endif
  void Begin();
  bool Read();
  inline SbusData data() const {return data_;}

 private:
  /* Communication */
  HardwareSerial *uart_;
  bool inv_ = true;
  bool fast_ = false;
  #if defined(ESP32)
  int8_t rxpin_, txpin_;
  #endif
  int32_t baud_ = 100000;
  /* Message len */
  static constexpr int8_t PAYLOAD_LEN_ = 23;
  static constexpr int8_t HEADER_LEN_ = 1;
  static constexpr int8_t FOOTER_LEN_ = 1;
  /* SBUS message defs */
  static constexpr int8_t NUM_SBUS_CH_ = 16;
  static constexpr uint8_t HEADER_ = 0x0F;
  static constexpr uint8_t FOOTER_ = 0x00;
  static constexpr uint8_t FOOTER2_ = 0x04;
  static constexpr uint8_t CH17_MASK_ = 0x01;
  static constexpr uint8_t CH18_MASK_ = 0x02;
  static constexpr uint8_t LOST_FRAME_MASK_ = 0x04;
  static constexpr uint8_t FAILSAFE_MASK_ = 0x08;
  /* Parsing state tracking */
  int8_t state_ = 0;
  uint8_t prev_byte_ = FOOTER_;
  uint8_t cur_byte_;
  /* Buffer for storing messages */
  uint8_t buf_[25];
  /* Data */
  bool new_data_;
  SbusData data_;
  bool Parse();
};

class SbusTx {
 public:
  #if defined(ESP32)
  SbusTx(HardwareSerial *bus, const int8_t rxpin, const int8_t txpin,
         const bool inv) : uart_(bus), inv_(inv), rxpin_(rxpin), txpin_(txpin)
         {}
  SbusTx(HardwareSerial *bus, const int8_t rxpin, const int8_t txpin,
         const bool inv, const bool fast) : uart_(bus), inv_(inv), fast_(fast),
                                            rxpin_(rxpin), txpin_(txpin) {}
  #else
  explicit SbusTx(HardwareSerial *bus) : uart_(bus) {}
  SbusTx(HardwareSerial *bus, const bool inv) : uart_(bus), inv_(inv) {}
  SbusTx(HardwareSerial *bus, const bool inv, const bool fast) : uart_(bus),
                                                                 inv_(inv),
                                                                 fast_(fast) {}
  #endif
  void Begin();
  void Write();
  inline void data(const SbusData &data) {data_ = data;}
  inline SbusData data() const {return data_;}

 private:
  /* Communication */
  HardwareSerial *uart_;
  bool inv_ = true;
  bool fast_ = false;
  #if defined(ESP32)
  int8_t rxpin_, txpin_;
  #endif
  int32_t baud_ = 100000;
  /* Message len */
  static constexpr int8_t BUF_LEN_ = 25;
  /* SBUS message defs */
  static constexpr int8_t NUM_SBUS_CH_ = 16;
  static constexpr uint8_t HEADER_ = 0x0F;
  static constexpr uint8_t FOOTER_ = 0x00;
  static constexpr uint8_t FOOTER2_ = 0x04;
  static constexpr uint8_t CH17_MASK_ = 0x01;
  static constexpr uint8_t CH18_MASK_ = 0x02;
  static constexpr uint8_t LOST_FRAME_MASK_ = 0x04;
  static constexpr uint8_t FAILSAFE_MASK_ = 0x08;
  /* Data */
  uint8_t buf_[BUF_LEN_];
  SbusData data_;
};

}  // namespace bfs

#endif  // SRC_SBUS_H_