sx127x.cpp

// Copyright (c) Sandeep Mistry. All rights reserved.
// Licensed under the MIT license.

// Modifications and additions copyright 2023 by Mark Qvist
// Obviously still under the MIT license.

#include "sx127x.h"

#define MCU_1284P 0x91
#define MCU_2560  0x92
#define MCU_ESP32 0x81
#define MCU_NRF52 0x71
#if defined(__AVR_ATmega1284P__)
  #define PLATFORM PLATFORM_AVR
  #define MCU_VARIANT MCU_1284P
#elif defined(__AVR_ATmega2560__)
  #define PLATFORM PLATFORM_AVR
  #define MCU_VARIANT MCU_2560
#elif defined(ESP32)
  #define PLATFORM PLATFORM_ESP32
  #define MCU_VARIANT MCU_ESP32
#elif defined(NRF52840_XXAA)
  #define PLATFORM PLATFORM_NRF52
  #define MCU_VARIANT MCU_NRF52
#endif

#ifndef MCU_VARIANT
  #error No MCU variant defined, cannot compile
#endif

#if MCU_VARIANT == MCU_ESP32
  #include "soc/rtc_wdt.h"
  #define ISR_VECT IRAM_ATTR
#else
  #define ISR_VECT
#endif

// Registers
#define REG_FIFO_7X                 0x00
#define REG_OP_MODE_7X              0x01
#define REG_FRF_MSB_7X              0x06
#define REG_FRF_MID_7X              0x07
#define REG_FRF_LSB_7X              0x08
#define REG_PA_CONFIG_7X            0x09
#define REG_OCP_7X                  0x0b
#define REG_LNA_7X                  0x0c
#define REG_FIFO_ADDR_PTR_7X        0x0d
#define REG_FIFO_TX_BASE_ADDR_7X    0x0e
#define REG_FIFO_RX_BASE_ADDR_7X    0x0f
#define REG_FIFO_RX_CURRENT_ADDR_7X 0x10
#define REG_IRQ_FLAGS_7X            0x12
#define REG_RX_NB_BYTES_7X          0x13
#define REG_MODEM_STAT_7X           0x18
#define REG_PKT_SNR_VALUE_7X        0x19
#define REG_PKT_RSSI_VALUE_7X       0x1a
#define REG_RSSI_VALUE_7X           0x1b
#define REG_MODEM_CONFIG_1_7X       0x1d
#define REG_MODEM_CONFIG_2_7X       0x1e
#define REG_PREAMBLE_MSB_7X         0x20
#define REG_PREAMBLE_LSB_7X         0x21
#define REG_PAYLOAD_LENGTH_7X       0x22
#define REG_MODEM_CONFIG_3_7X       0x26
#define REG_FREQ_ERROR_MSB_7X       0x28
#define REG_FREQ_ERROR_MID_7X       0x29
#define REG_FREQ_ERROR_LSB_7X       0x2a
#define REG_RSSI_WIDEBAND_7X        0x2c
#define REG_DETECTION_OPTIMIZE_7X   0x31
#define REG_HIGH_BW_OPTIMIZE_1_7X   0x36
#define REG_DETECTION_THRESHOLD_7X  0x37
#define REG_SYNC_WORD_7X            0x39
#define REG_HIGH_BW_OPTIMIZE_2_7X   0x3a
#define REG_DIO_MAPPING_1_7X        0x40
#define REG_VERSION_7X              0x42
#define REG_TCXO_7X                 0x4b
#define REG_PA_DAC_7X               0x4d

// Modes
#define MODE_LONG_RANGE_MODE_7X     0x80
#define MODE_SLEEP_7X               0x00
#define MODE_STDBY_7X               0x01
#define MODE_TX_7X                  0x03
#define MODE_RX_CONTINUOUS_7X       0x05
#define MODE_RX_SINGLE_7X           0x06

// PA config
#define PA_BOOST_7X                 0x80

// IRQ masks
#define IRQ_TX_DONE_MASK_7X         0x08
#define IRQ_PAYLOAD_CRC_ERROR_MASK_7X 0x20
#define IRQ_RX_DONE_MASK_7X         0x40

extern SPIClass SPI;

#define MAX_PKT_LENGTH           255

sx127x::sx127x() :
  _spiSettings(8E6, MSBFIRST, SPI_MODE0),
  _ss(LORA_DEFAULT_SS_PIN), _reset(LORA_DEFAULT_RESET_PIN), _dio0(LORA_DEFAULT_DIO0_PIN),
  _frequency(0),
  _packetIndex(0),
  _preinit_done(false),
  _onReceive(NULL)
{
  // overide Stream timeout value
  setTimeout(0);
}

bool sx127x::preInit() {
  // setup pins
  pinMode(_ss, OUTPUT);
  // set SS high
  digitalWrite(_ss, HIGH);
  
  SPI.begin();

  // check version (retry for up to 2 seconds)
  uint8_t version;
  long start = millis();
  while (((millis() - start) < 2000) && (millis() >= start)) {
      version = readRegister(REG_VERSION_7X);
      if (version == 0x12) {
          break;
      }
      delay(100);
  }
  if (version != 0x12) {
      return false;
  }

  _preinit_done = true;
  return true;
}

uint8_t ISR_VECT sx127x::readRegister(uint8_t address)
{
  return singleTransfer(address & 0x7f, 0x00);
}

void sx127x::writeRegister(uint8_t address, uint8_t value)
{
  singleTransfer(address | 0x80, value);
}

uint8_t ISR_VECT sx127x::singleTransfer(uint8_t address, uint8_t value)
{
  uint8_t response;

  digitalWrite(_ss, LOW);

  SPI.beginTransaction(_spiSettings);
  SPI.transfer(address);
  response = SPI.transfer(value);
  SPI.endTransaction();

  digitalWrite(_ss, HIGH);

  return response;
}


int sx127x::begin(long frequency)
{
  if (_reset != -1) {
    pinMode(_reset, OUTPUT);

    // perform reset
    digitalWrite(_reset, LOW);
    delay(10);
    digitalWrite(_reset, HIGH);
    delay(10);
  }

  if (_busy != -1) {
      pinMode(_busy, INPUT);
  }

  if (!_preinit_done) {
    if (!preInit()) {
      return false;
    }
  }

  // put in sleep mode
  sleep();

  // set frequency
  setFrequency(frequency);

  // set base addresses
  writeRegister(REG_FIFO_TX_BASE_ADDR_7X, 0);
  writeRegister(REG_FIFO_RX_BASE_ADDR_7X, 0);

  // set LNA boost
  writeRegister(REG_LNA_7X, readRegister(REG_LNA_7X) | 0x03);

  // set auto AGC
  writeRegister(REG_MODEM_CONFIG_3_7X, 0x04);

  // set output power to 2 dBm
  setTxPower(2);

  // put in standby mode
  idle();

  return 1;
}

void sx127x::end()
{
  // put in sleep mode
  sleep();

  // stop SPI
  SPI.end();

  _preinit_done = false;
}

int sx127x::beginPacket(int implicitHeader)
{
  // put in standby mode
  idle();

  if (implicitHeader) {
    implicitHeaderMode();
  } else {
    explicitHeaderMode();
  }

  // reset FIFO address and payload length
  writeRegister(REG_FIFO_ADDR_PTR_7X, 0);
  writeRegister(REG_PAYLOAD_LENGTH_7X, 0);

  return 1;
}

int sx127x::endPacket()
{
  // put in TX mode
  writeRegister(REG_OP_MODE_7X, MODE_LONG_RANGE_MODE_7X | MODE_TX_7X);

  // wait for TX done
  while ((readRegister(REG_IRQ_FLAGS_7X) & IRQ_TX_DONE_MASK_7X) == 0) {
    yield();
  }

  // clear IRQ's
  writeRegister(REG_IRQ_FLAGS_7X, IRQ_TX_DONE_MASK_7X);
  return 1;
}

uint8_t sx127x::modemStatus() {
    return readRegister(REG_MODEM_STAT_7X);
}


uint8_t sx127x::currentRssiRaw() {
    uint8_t rssi = readRegister(REG_RSSI_VALUE_7X);
    return rssi;
}

int ISR_VECT sx127x::currentRssi() {
    int rssi = (int)readRegister(REG_RSSI_VALUE_7X) - RSSI_OFFSET;
    if (_frequency < 820E6) rssi -= 7;
    return rssi;
}

uint8_t sx127x::packetRssiRaw() {
    uint8_t pkt_rssi_value = readRegister(REG_PKT_RSSI_VALUE_7X);
    return pkt_rssi_value;
}

int ISR_VECT sx127x::packetRssi() {
    int pkt_rssi = (int)readRegister(REG_PKT_RSSI_VALUE_7X) - RSSI_OFFSET;
    int pkt_snr = packetSnr();

    if (_frequency < 820E6) pkt_rssi -= 7;

    if (pkt_snr < 0) {
        pkt_rssi += pkt_snr;
    } else {
        // Slope correction is (16/15)*pkt_rssi,
        // this estimation looses one floating point
        // operation, and should be precise enough.
        pkt_rssi = (int)(1.066 * pkt_rssi);
    }
    return pkt_rssi;
}

uint8_t ISR_VECT sx127x::packetSnrRaw() {
    return readRegister(REG_PKT_SNR_VALUE_7X);
}

float ISR_VECT sx127x::packetSnr() {
    return ((int8_t)readRegister(REG_PKT_SNR_VALUE_7X)) * 0.25;
}

long sx127x::packetFrequencyError()
{
  int32_t freqError = 0;
  freqError = static_cast<int32_t>(readRegister(REG_FREQ_ERROR_MSB_7X) & B111);
  freqError <<= 8L;
  freqError += static_cast<int32_t>(readRegister(REG_FREQ_ERROR_MID_7X));
  freqError <<= 8L;
  freqError += static_cast<int32_t>(readRegister(REG_FREQ_ERROR_LSB_7X));

  if (readRegister(REG_FREQ_ERROR_MSB_7X) & B1000) { // Sign bit is on
      freqError -= 524288; // B1000'0000'0000'0000'0000
  }

  const float fXtal = 32E6; // FXOSC: crystal oscillator (XTAL) frequency (2.5. Chip Specification, p. 14)
  const float fError = ((static_cast<float>(freqError) * (1L << 24)) / fXtal) * (getSignalBandwidth() / 500000.0f); // p. 37

  return static_cast<long>(fError);
}

size_t sx127x::write(uint8_t byte)
{
  return write(&byte, sizeof(byte));
}

size_t sx127x::write(const uint8_t *buffer, size_t size)
{
    int currentLength = readRegister(REG_PAYLOAD_LENGTH_7X);

    // check size
    if ((currentLength + size) > MAX_PKT_LENGTH) {
        size = MAX_PKT_LENGTH - currentLength;
    }

    // write data
    for (size_t i = 0; i < size; i++) {
        writeRegister(REG_FIFO_7X, buffer[i]);
    }

    // update length
    writeRegister(REG_PAYLOAD_LENGTH_7X, currentLength + size);
    return size;
}

int ISR_VECT sx127x::available()
{
    return (readRegister(REG_RX_NB_BYTES_7X) - _packetIndex);
}

int ISR_VECT sx127x::read()
{
  if (!available()) {
    return -1;
  }

  _packetIndex++;
  return readRegister(REG_FIFO_7X);
}

int sx127x::peek()
{
  if (!available()) {
    return -1;
  }

  // store current FIFO address
  int currentAddress = readRegister(REG_FIFO_ADDR_PTR_7X);

  // read
  uint8_t b = readRegister(REG_FIFO_7X);

  // restore FIFO address
  writeRegister(REG_FIFO_ADDR_PTR_7X, currentAddress);

  return b;
}

void sx127x::flush()
{
}

void sx127x::onReceive(void(*callback)(int))
{
  _onReceive = callback;

  if (callback) {
    pinMode(_dio0, INPUT);

    writeRegister(REG_DIO_MAPPING_1_7X, 0x00);
#ifdef SPI_HAS_NOTUSINGINTERRUPT
    SPI.usingInterrupt(digitalPinToInterrupt(_dio0));
#endif
    attachInterrupt(digitalPinToInterrupt(_dio0), sx127x::onDio0Rise, RISING);
  } else {
    detachInterrupt(digitalPinToInterrupt(_dio0));
#ifdef SPI_HAS_NOTUSINGINTERRUPT
    SPI.notUsingInterrupt(digitalPinToInterrupt(_dio0));
#endif
  }
}

void sx127x::receive(int size)
{
    if (size > 0) {
        implicitHeaderMode();

        writeRegister(REG_PAYLOAD_LENGTH_7X, size & 0xff);
    } else {
        explicitHeaderMode();
    }

    writeRegister(REG_OP_MODE_7X, MODE_LONG_RANGE_MODE_7X | MODE_RX_CONTINUOUS_7X);
}

void sx127x::idle()
{
    writeRegister(REG_OP_MODE_7X, MODE_LONG_RANGE_MODE_7X | MODE_STDBY_7X);
}

void sx127x::sleep()
{
    writeRegister(REG_OP_MODE_7X, MODE_LONG_RANGE_MODE_7X | MODE_SLEEP_7X);
}

void sx127x::enableTCXO() {
    uint8_t tcxo_reg = readRegister(REG_TCXO_7X);
    writeRegister(REG_TCXO_7X, tcxo_reg | 0x10);
}

void sx127x::disableTCXO() {
      uint8_t tcxo_reg = readRegister(REG_TCXO_7X);
      writeRegister(REG_TCXO_7X, tcxo_reg & 0xEF);
}

void sx127x::setTxPower(int level, int outputPin) {
    if (PA_OUTPUT_RFO_PIN == outputPin) {
        // RFO
        if (level < 0) {
            level = 0;
        } else if (level > 14) {
            level = 14;
        }

        writeRegister(REG_PA_DAC_7X, 0x84);
        writeRegister(REG_PA_CONFIG_7X, 0x70 | level);

    } else {
        // PA BOOST
        if (level < 2) {
            level = 2;
        } else if (level > 17) {
            level = 17;
        }

        writeRegister(REG_PA_DAC_7X, 0x84);
        writeRegister(REG_PA_CONFIG_7X, PA_BOOST_7X | (level - 2));
    }
}

uint8_t sx127x::getTxPower() {
    byte txp = readRegister(REG_PA_CONFIG_7X);
    return txp;
}

void sx127x::setFrequency(unsigned long frequency) {
  _frequency = frequency;

  uint32_t frf = ((uint64_t)frequency << 19) / 32000000;

  writeRegister(REG_FRF_MSB_7X, (uint8_t)(frf >> 16));
  writeRegister(REG_FRF_MID_7X, (uint8_t)(frf >> 8));
  writeRegister(REG_FRF_LSB_7X, (uint8_t)(frf >> 0));

  optimizeModemSensitivity();
}

uint32_t sx127x::getFrequency() {
    uint8_t msb = readRegister(REG_FRF_MSB_7X);
    uint8_t mid = readRegister(REG_FRF_MID_7X);
    uint8_t lsb = readRegister(REG_FRF_LSB_7X);

    uint32_t frf = ((uint32_t)msb << 16) | ((uint32_t)mid << 8) | (uint32_t)lsb;
    uint64_t frm = (uint64_t)frf*32000000;
    uint32_t frequency = (frm >> 19);

    return frequency;
}

void sx127x::setSpreadingFactor(int sf)
{
  if (sf < 6) {
    sf = 6;
  } else if (sf > 12) {
    sf = 12;
  }

  if (sf == 6) {
      writeRegister(REG_DETECTION_OPTIMIZE_7X, 0xc5);
      writeRegister(REG_DETECTION_THRESHOLD_7X, 0x0c);
  } else {
      writeRegister(REG_DETECTION_OPTIMIZE_7X, 0xc3);
      writeRegister(REG_DETECTION_THRESHOLD_7X, 0x0a);
  }

  writeRegister(REG_MODEM_CONFIG_2_7X, (readRegister(REG_MODEM_CONFIG_2_7X) & 0x0f) | ((sf << 4) & 0xf0));
  handleLowDataRate();
}

long sx127x::getSignalBandwidth()
{
      byte bw = (readRegister(REG_MODEM_CONFIG_1_7X) >> 4);
      switch (bw) {
        case 0: return 7.8E3;
        case 1: return 10.4E3;
        case 2: return 15.6E3;
        case 3: return 20.8E3;
        case 4: return 31.25E3;
        case 5: return 41.7E3;
        case 6: return 62.5E3;
        case 7: return 125E3;
        case 8: return 250E3;
        case 9: return 500E3;
      }
  return 0;
}

void sx127x::handleLowDataRate(){
    int sf = (readRegister(REG_MODEM_CONFIG_2_7X) >> 4);
    if ( long( (1<<sf) / (getSignalBandwidth()/1000)) > 16) {
        // set auto AGC and LowDataRateOptimize
        writeRegister(REG_MODEM_CONFIG_3_7X, (1<<3)|(1<<2));
    } else {
        // set auto AGC
        writeRegister(REG_MODEM_CONFIG_3_7X, (1<<2));
    }
}

void sx127x::optimizeModemSensitivity(){
    byte bw = (readRegister(REG_MODEM_CONFIG_1_7X) >> 4);
    uint32_t freq = getFrequency();

    if (bw == 9 && (410E6 <= freq) && (freq <= 525E6)) {
        writeRegister(REG_HIGH_BW_OPTIMIZE_1_7X, 0x02);
        writeRegister(REG_HIGH_BW_OPTIMIZE_2_7X, 0x7f);
    } else if (bw == 9 && (820E6 <= freq) && (freq <= 1020E6)) {
        writeRegister(REG_HIGH_BW_OPTIMIZE_1_7X, 0x02);
        writeRegister(REG_HIGH_BW_OPTIMIZE_2_7X, 0x64);
    } else {
        writeRegister(REG_HIGH_BW_OPTIMIZE_1_7X, 0x03);
    }
}

void sx127x::setSignalBandwidth(long sbw)
{
    int bw;

    if (sbw <= 7.8E3) {
        bw = 0;
    } else if (sbw <= 10.4E3) {
        bw = 1;
    } else if (sbw <= 15.6E3) {
        bw = 2;
    } else if (sbw <= 20.8E3) {
        bw = 3;
    } else if (sbw <= 31.25E3) {
        bw = 4;
    } else if (sbw <= 41.7E3) {
        bw = 5;
    } else if (sbw <= 62.5E3) {
        bw = 6;
    } else if (sbw <= 125E3) {
        bw = 7;
    } else if (sbw <= 250E3) {
        bw = 8;
    } else /*if (sbw <= 250E3)*/ {
        bw = 9;
    }

    writeRegister(REG_MODEM_CONFIG_1_7X, (readRegister(REG_MODEM_CONFIG_1_7X) & 0x0f) | (bw << 4));


  handleLowDataRate();
  optimizeModemSensitivity();
}

void sx127x::setCodingRate4(int denominator)
{
  if (denominator < 5) {
    denominator = 5;
  } else if (denominator > 8) {
    denominator = 8;
  }

  int cr = denominator - 4;

  writeRegister(REG_MODEM_CONFIG_1_7X, (readRegister(REG_MODEM_CONFIG_1_7X) & 0xf1) | (cr << 1));
}

void sx127x::setPreambleLength(long length)
{
  writeRegister(REG_PREAMBLE_MSB_7X, (uint8_t)(length >> 8));
  writeRegister(REG_PREAMBLE_LSB_7X, (uint8_t)(length >> 0));
}

void sx127x::setSyncWord(int sw)
{
    writeRegister(REG_SYNC_WORD_7X, sw);
}

void sx127x::enableCrc()
{
    writeRegister(REG_MODEM_CONFIG_2_7X, readRegister(REG_MODEM_CONFIG_2_7X) | 0x04);
}

void sx127x::disableCrc()
{
    writeRegister(REG_MODEM_CONFIG_2_7X, readRegister(REG_MODEM_CONFIG_2_7X) & 0xfb);
}

byte sx127x::random()
{
    return readRegister(REG_RSSI_WIDEBAND_7X);
}

void sx127x::setPins(int ss, int reset, int dio0, int busy)
{
  _ss = ss;
  _reset = reset;
  _dio0 = dio0;
  _busy = busy;
}

void sx127x::setSPIFrequency(uint32_t frequency)
{
  _spiSettings = SPISettings(frequency, MSBFIRST, SPI_MODE0);
}

void sx127x::dumpRegisters(Stream& out)
{
  for (int i = 0; i < 128; i++) {
    out.print("0x");
    out.print(i, HEX);
    out.print(": 0x");
    out.println(readRegister(i), HEX);
  }
}

void sx127x::explicitHeaderMode()
{
  _implicitHeaderMode = 0;

  writeRegister(REG_MODEM_CONFIG_1_7X, readRegister(REG_MODEM_CONFIG_1_7X) & 0xfe);
}

void sx127x::implicitHeaderMode()
{
  _implicitHeaderMode = 1;

  writeRegister(REG_MODEM_CONFIG_1_7X, readRegister(REG_MODEM_CONFIG_1_7X) | 0x01);
}


void ISR_VECT sx127x::handleDio0Rise()
{
    int irqFlags = readRegister(REG_IRQ_FLAGS_7X);

    // clear IRQ's
    writeRegister(REG_IRQ_FLAGS_7X, irqFlags);
    if ((irqFlags & IRQ_PAYLOAD_CRC_ERROR_MASK_7X) == 0) {

        // received a packet
        _packetIndex = 0;

        // read packet length
        int packetLength = _implicitHeaderMode ? readRegister(REG_PAYLOAD_LENGTH_7X) : readRegister(REG_RX_NB_BYTES_7X);

        // set FIFO address to current RX address
        writeRegister(REG_FIFO_ADDR_PTR_7X, readRegister(REG_FIFO_RX_CURRENT_ADDR_7X));

        if (_onReceive) {
            _onReceive(packetLength);
        }

        // reset FIFO address
        writeRegister(REG_FIFO_ADDR_PTR_7X, 0);
    }
}

void ISR_VECT sx127x::onDio0Rise()
{
  sx127x_modem.handleDio0Rise();
}

sx127x sx127x_modem;