text: // **********************************************************************************
  // Driver definition for HopeRF RFM69W/RFM69HW/RFM69CW/RFM69HCW, Semtech SX1231/1231H
  // **********************************************************************************
  // Copyright LowPowerLab LLC 2018, https://www.LowPowerLab.com/contact
  // **********************************************************************************
  // License
  // **********************************************************************************
  // This program is free software; you can redistribute it 
  // and/or modify it under the terms of the GNU General    
  // Public License as published by the Free Software       
  // Foundation; either version 3 of the License, or        
  // (at your option) any later version.                    
  //                                                        
  // This program is distributed in the hope that it will   
  // be useful, but WITHOUT ANY WARRANTY; without even the  
  // implied warranty of MERCHANTABILITY or FITNESS FOR A   
  // PARTICULAR PURPOSE. See the GNU General Public        
  // License for more details.                              
  //                                                        
  // Licence can be viewed at                               
  // http://www.gnu.org/licenses/gpl-3.0.txt
  //
  // Please maintain this license information along with authorship
  // and copyright notices in any redistribution of this code
  // **********************************************************************************
  #include <RFM69.h>
  #include <RFM69registers.h>
  #include <SPI.h>
  
  uint8_t RFM69::DATA[RF69_MAX_DATA_LEN];
  uint8_t RFM69::_mode;        // current transceiver state
  uint8_t RFM69::DATALEN;
  uint16_t RFM69::SENDERID;
  uint16_t RFM69::TARGETID;     // should match _address
  uint8_t RFM69::PAYLOADLEN;
  uint8_t RFM69::ACK_REQUESTED;
  uint8_t RFM69::ACK_RECEIVED; // should be polled immediately after sending a packet with ACK request
  int16_t RFM69::RSSI;          // most accurate RSSI during reception (closest to the reception)
  volatile bool RFM69::_haveData;
  RFM69* RFM69::selfPointer;
  
  RFM69::RFM69(uint8_t slaveSelectPin, uint8_t interruptPin, bool isRFM69HW)
  {
    _slaveSelectPin = slaveSelectPin;
    _interruptPin = interruptPin;
    _mode = RF69_MODE_STANDBY;
    _promiscuousMode = false;
    _powerLevel = 31;
    _isRFM69HW = isRFM69HW;
  #if defined(RF69_LISTENMODE_ENABLE)
    _isHighSpeed = true;
    _haveEncryptKey = false;
    uint32_t rxDuration = DEFAULT_LISTEN_RX_US;
    uint32_t idleDuration = DEFAULT_LISTEN_IDLE_US;
    listenModeSetDurations(rxDuration, idleDuration);
  #endif
  }
  
  bool RFM69::initialize(uint8_t freqBand, uint16_t nodeID, uint8_t networkID)
  {
    _interruptNum = digitalPinToInterrupt(_interruptPin);
    if (_interruptNum == NOT_AN_INTERRUPT) return false;
  #ifdef RF69_ATTACHINTERRUPT_TAKES_PIN_NUMBER
      _interruptNum = _interruptPin;
  #endif
    const uint8_t CONFIG[][2] =
    {
      /* 0x01 */ { REG_OPMODE, RF_OPMODE_SEQUENCER_ON | RF_OPMODE_LISTEN_OFF | RF_OPMODE_STANDBY },
      /* 0x02 */ { REG_DATAMODUL, RF_DATAMODUL_DATAMODE_PACKET | RF_DATAMODUL_MODULATIONTYPE_FSK | RF_DATAMODUL_MODULATIONSHAPING_00 }, // no shaping
      /* 0x03 */ { REG_BITRATEMSB, RF_BITRATEMSB_55555}, // default: 4.8 KBPS
      /* 0x04 */ { REG_BITRATELSB, RF_BITRATELSB_55555},
      /* 0x05 */ { REG_FDEVMSB, RF_FDEVMSB_50000}, // default: 5KHz, (FDEV + BitRate / 2 <= 500KHz)
      /* 0x06 */ { REG_FDEVLSB, RF_FDEVLSB_50000},
  
      /* 0x07 */ { REG_FRFMSB, (uint8_t) (freqBand==RF69_315MHZ ? RF_FRFMSB_315 : (freqBand==RF69_433MHZ ? RF_FRFMSB_433 : (freqBand==RF69_868MHZ ? RF_FRFMSB_868 : RF_FRFMSB_915))) },
      /* 0x08 */ { REG_FRFMID, (uint8_t) (freqBand==RF69_315MHZ ? RF_FRFMID_315 : (freqBand==RF69_433MHZ ? RF_FRFMID_433 : (freqBand==RF69_868MHZ ? RF_FRFMID_868 : RF_FRFMID_915))) },
      /* 0x09 */ { REG_FRFLSB, (uint8_t) (freqBand==RF69_315MHZ ? RF_FRFLSB_315 : (freqBand==RF69_433MHZ ? RF_FRFLSB_433 : (freqBand==RF69_868MHZ ? RF_FRFLSB_868 : RF_FRFLSB_915))) },
  
      // looks like PA1 and PA2 are not implemented on RFM69W, hence the max output power is 13dBm
      // +17dBm and +20dBm are possible on RFM69HW
      // +13dBm formula: Pout = -18 + OutputPower (with PA0 or PA1**)
      // +17dBm formula: Pout = -14 + OutputPower (with PA1 and PA2)**
      // +20dBm formula: Pout = -11 + OutputPower (with PA1 and PA2)** and high power PA settings (section 3.3.7 in datasheet)
      ///* 0x11 */ { REG_PALEVEL, RF_PALEVEL_PA0_ON | RF_PALEVEL_PA1_OFF | RF_PALEVEL_PA2_OFF | RF_PALEVEL_OUTPUTPOWER_11111},
      ///* 0x13 */ { REG_OCP, RF_OCP_ON | RF_OCP_TRIM_95 }, // over current protection (default is 95mA)
  
      // RXBW defaults are { REG_RXBW, RF_RXBW_DCCFREQ_010 | RF_RXBW_MANT_24 | RF_RXBW_EXP_5} (RxBw: 10.4KHz)
      /* 0x19 */ { REG_RXBW, RF_RXBW_DCCFREQ_010 | RF_RXBW_MANT_16 | RF_RXBW_EXP_2 }, // (BitRate < 2 * RxBw)
      //for BR-19200: /* 0x19 */ { REG_RXBW, RF_RXBW_DCCFREQ_010 | RF_RXBW_MANT_24 | RF_RXBW_EXP_3 },
      /* 0x25 */ { REG_DIOMAPPING1, RF_DIOMAPPING1_DIO0_01 }, // DIO0 is the only IRQ we're using
      /* 0x26 */ { REG_DIOMAPPING2, RF_DIOMAPPING2_CLKOUT_OFF }, // DIO5 ClkOut disable for power saving
      /* 0x28 */ { REG_IRQFLAGS2, RF_IRQFLAGS2_FIFOOVERRUN }, // writing to this bit ensures that the FIFO & status flags are reset
      /* 0x29 */ { REG_RSSITHRESH, 220 }, // must be set to dBm = (-Sensitivity / 2), default is 0xE4 = 228 so -114dBm
      ///* 0x2D */ { REG_PREAMBLELSB, RF_PREAMBLESIZE_LSB_VALUE } // default 3 preamble bytes 0xAAAAAA
      /* 0x2E */ { REG_SYNCCONFIG, RF_SYNC_ON | RF_SYNC_FIFOFILL_AUTO | RF_SYNC_SIZE_2 | RF_SYNC_TOL_0 },
      /* 0x2F */ { REG_SYNCVALUE1, 0x2D },      // attempt to make this compatible with sync1 byte of RFM12B lib
      /* 0x30 */ { REG_SYNCVALUE2, networkID }, // NETWORK ID
      /* 0x37 */ { REG_PACKETCONFIG1, RF_PACKET1_FORMAT_VARIABLE | RF_PACKET1_DCFREE_OFF | RF_PACKET1_CRC_ON | RF_PACKET1_CRCAUTOCLEAR_ON | RF_PACKET1_ADRSFILTERING_OFF },
      /* 0x38 */ { REG_PAYLOADLENGTH, 66 }, // in variable length mode: the max frame size, not used in TX
      ///* 0x39 */ { REG_NODEADRS, nodeID }, // turned off because we're not using address filtering
      /* 0x3C */ { REG_FIFOTHRESH, RF_FIFOTHRESH_TXSTART_FIFONOTEMPTY | RF_FIFOTHRESH_VALUE }, // TX on FIFO not empty
      /* 0x3D */ { REG_PACKETCONFIG2, RF_PACKET2_RXRESTARTDELAY_2BITS | RF_PACKET2_AUTORXRESTART_ON | RF_PACKET2_AES_OFF }, // RXRESTARTDELAY must match transmitter PA ramp-down time (bitrate dependent)
      //for BR-19200: /* 0x3D */ { REG_PACKETCONFIG2, RF_PACKET2_RXRESTARTDELAY_NONE | RF_PACKET2_AUTORXRESTART_ON | RF_PACKET2_AES_OFF }, // RXRESTARTDELAY must match transmitter PA ramp-down time (bitrate dependent)
      /* 0x6F */ { REG_TESTDAGC, RF_DAGC_IMPROVED_LOWBETA0 }, // run DAGC continuously in RX mode for Fading Margin Improvement, recommended default for AfcLowBetaOn=0
      {255, 0}
    };
  
    digitalWrite(_slaveSelectPin, HIGH);
    pinMode(_slaveSelectPin, OUTPUT);
    SPI.begin();
    
  #ifdef SPI_HAS_TRANSACTION
    _settings = SPISettings(4000000, MSBFIRST, SPI_MODE0);
  #endif
  
    unsigned long start = millis();
    uint8_t timeout = 50;
    do writeReg(REG_SYNCVALUE1, 0xAA); while (readReg(REG_SYNCVALUE1) != 0xaa && millis()-start < timeout);
    start = millis();
    do writeReg(REG_SYNCVALUE1, 0x55); while (readReg(REG_SYNCVALUE1) != 0x55 && millis()-start < timeout);
  
    for (uint8_t i = 0; CONFIG[i][0] != 255; i++)
      writeReg(CONFIG[i][0], CONFIG[i][1]);
  
    // Encryption is persistent between resets and can trip you up during debugging.
    // Disable it during initialization so we always start from a known state.
    encrypt(0);
  
    setHighPower(_isRFM69HW); // called regardless if it's a RFM69W or RFM69HW
    setMode(RF69_MODE_STANDBY);
    start = millis();
    while (((readReg(REG_IRQFLAGS1) & RF_IRQFLAGS1_MODEREADY) == 0x00) && millis()-start < timeout); // wait for ModeReady
    if (millis()-start >= timeout)
      return false;
    attachInterrupt(_interruptNum, RFM69::isr0, RISING);
  
    selfPointer = this;
    _address = nodeID;
  #if defined(RF69_LISTENMODE_ENABLE)
    _freqBand = freqBand;
    _networkID = networkID;
  #endif
    return true;
  }
  
  // return the frequency (in Hz)
  uint32_t RFM69::getFrequency()
  {
    return RF69_FSTEP * (((uint32_t) readReg(REG_FRFMSB) << 16) + ((uint16_t) readReg(REG_FRFMID) << 8) + readReg(REG_FRFLSB));
  }
  
  // set the frequency (in Hz)
  void RFM69::setFrequency(uint32_t freqHz)
  {
    uint8_t oldMode = _mode;
    if (oldMode == RF69_MODE_TX) {
      setMode(RF69_MODE_RX);
    }
    freqHz /= RF69_FSTEP; // divide down by FSTEP to get FRF
    writeReg(REG_FRFMSB, freqHz >> 16);
    writeReg(REG_FRFMID, freqHz >> 8);
    writeReg(REG_FRFLSB, freqHz);
    if (oldMode == RF69_MODE_RX) {
      setMode(RF69_MODE_SYNTH);
    }
    setMode(oldMode);
  }
  
  void RFM69::setMode(uint8_t newMode)
  {
    if (newMode == _mode)
      return;
  
    switch (newMode) {
      case RF69_MODE_TX:
        writeReg(REG_OPMODE, (readReg(REG_OPMODE) & 0xE3) | RF_OPMODE_TRANSMITTER);
        if (_isRFM69HW) setHighPowerRegs(true);
        break;
      case RF69_MODE_RX:
        writeReg(REG_OPMODE, (readReg(REG_OPMODE) & 0xE3) | RF_OPMODE_RECEIVER);
        if (_isRFM69HW) setHighPowerRegs(false);
        break;
      case RF69_MODE_SYNTH:
        writeReg(REG_OPMODE, (readReg(REG_OPMODE) & 0xE3) | RF_OPMODE_SYNTHESIZER);
        break;
      case RF69_MODE_STANDBY:
        writeReg(REG_OPMODE, (readReg(REG_OPMODE) & 0xE3) | RF_OPMODE_STANDBY);
        break;
      case RF69_MODE_SLEEP:
        writeReg(REG_OPMODE, (readReg(REG_OPMODE) & 0xE3) | RF_OPMODE_SLEEP);
        break;
      default:
        return;
    }
  
    // we are using packet mode, so this check is not really needed
    // but waiting for mode ready is necessary when going from sleep because the FIFO may not be immediately available from previous mode
    while (_mode == RF69_MODE_SLEEP && (readReg(REG_IRQFLAGS1) & RF_IRQFLAGS1_MODEREADY) == 0x00); // wait for ModeReady
  
    _mode = newMode;
  }
  
  //put transceiver in sleep mode to save battery - to wake or resume receiving just call receiveDone()
  void RFM69::sleep() {
    setMode(RF69_MODE_SLEEP);
  }
  
  //set this node's address
  void RFM69::setAddress(uint16_t addr)
  {
    _address = addr;
    writeReg(REG_NODEADRS, _address); //unused in packet mode
  }
  
  //set this node's network id
  void RFM69::setNetwork(uint8_t networkID)
  {
    writeReg(REG_SYNCVALUE2, networkID);
  }
  
  // set *transmit/TX* output power: 0=min, 31=max
  // this results in a "weaker" transmitted signal, and directly results in a lower RSSI at the receiver
  // the power configurations are explained in the SX1231H datasheet (Table 10 on p21; RegPaLevel p66): http://www.semtech.com/images/datasheet/sx1231h.pdf
  // valid powerLevel parameter values are 0-31 and result in a directly proportional effect on the output/transmission power
  // this function implements 2 modes as follows:
  //       - for RFM69W the range is from 0-31 [-18dBm to 13dBm] (PA0 only on RFIO pin)
  //       - for RFM69HW the range is from 0-31 [5dBm to 20dBm]  (PA1 & PA2 on PA_BOOST pin & high Power PA settings - see section 3.3.7 in datasheet, p22)
  void RFM69::setPowerLevel(uint8_t powerLevel)
  {
    _powerLevel = (powerLevel > 31 ? 31 : powerLevel);
    if (_isRFM69HW) _powerLevel /= 2;
    writeReg(REG_PALEVEL, (readReg(REG_PALEVEL) & 0xE0) | _powerLevel);
  }
  
  bool RFM69::canSend()
  {
    if (_mode == RF69_MODE_RX && PAYLOADLEN == 0 && readRSSI() < CSMA_LIMIT) // if signal stronger than -100dBm is detected assume channel activity
    {
      setMode(RF69_MODE_STANDBY);
      return true;
    }
    return false;
  }
  
  void RFM69::send(uint16_t toAddress, const void* buffer, uint8_t bufferSize, bool requestACK)
  {
    writeReg(REG_PACKETCONFIG2, (readReg(REG_PACKETCONFIG2) & 0xFB) | RF_PACKET2_RXRESTART); // avoid RX deadlocks
    uint32_t now = millis();
    while (!canSend() && millis() - now < RF69_CSMA_LIMIT_MS) receiveDone();
    sendFrame(toAddress, buffer, bufferSize, requestACK, false);
  }
  
  // to increase the chance of getting a packet across, call this function instead of send
  // and it handles all the ACK requesting/retrying for you :)
  // The only twist is that you have to manually listen to ACK requests on the other side and send back the ACKs
  // The reason for the semi-automaton is that the lib is interrupt driven and
  // requires user action to read the received data and decide what to do with it
  // replies usually take only 5..8ms at 50kbps@915MHz
  bool RFM69::sendWithRetry(uint16_t toAddress, const void* buffer, uint8_t bufferSize, uint8_t retries, uint8_t retryWaitTime) {
    uint32_t sentTime;
    for (uint8_t i = 0; i <= retries; i++)
    {
      send(toAddress, buffer, bufferSize, true);
      sentTime = millis();
      while (millis() - sentTime < retryWaitTime)
      {
        if (ACKReceived(toAddress)) return true;
      }
    }
    return false;
  }
  
  // should be polled immediately after sending a packet with ACK request
  bool RFM69::ACKReceived(uint16_t fromNodeID) {
    if (receiveDone())
      return (SENDERID == fromNodeID || fromNodeID == RF69_BROADCAST_ADDR) && ACK_RECEIVED;
    return false;
  }
  
  // check whether an ACK was requested in the last received packet (non-broadcasted packet)
  bool RFM69::ACKRequested() {
    return ACK_REQUESTED && (TARGETID != RF69_BROADCAST_ADDR);
  }
  
  // should be called immediately after reception in case sender wants ACK
  void RFM69::sendACK(const void* buffer, uint8_t bufferSize) {
    ACK_REQUESTED = 0;   // TWS added to make sure we don't end up in a timing race and infinite loop sending Acks
    uint16_t sender = SENDERID;
    int16_t _RSSI = RSSI; // save payload received RSSI value
    writeReg(REG_PACKETCONFIG2, (readReg(REG_PACKETCONFIG2) & 0xFB) | RF_PACKET2_RXRESTART); // avoid RX deadlocks
    uint32_t now = millis();
    while (!canSend() && millis() - now < RF69_CSMA_LIMIT_MS) receiveDone();
    SENDERID = sender;    // TWS: Restore SenderID after it gets wiped out by receiveDone()
    sendFrame(sender, buffer, bufferSize, false, true);
    RSSI = _RSSI; // restore payload RSSI
  }
  
  // internal function
  void RFM69::sendFrame(uint16_t toAddress, const void* buffer, uint8_t bufferSize, bool requestACK, bool sendACK)
  {
    setMode(RF69_MODE_STANDBY); // turn off receiver to prevent reception while filling fifo
    while ((readReg(REG_IRQFLAGS1) & RF_IRQFLAGS1_MODEREADY) == 0x00); // wait for ModeReady
    writeReg(REG_DIOMAPPING1, RF_DIOMAPPING1_DIO0_00); // DIO0 is "Packet Sent"
    if (bufferSize > RF69_MAX_DATA_LEN) bufferSize = RF69_MAX_DATA_LEN;
  
    // control byte
    uint8_t CTLbyte = 0x00;
    if (sendACK)
      CTLbyte = RFM69_CTL_SENDACK;
    else if (requestACK)
      CTLbyte = RFM69_CTL_REQACK;
  
    if (toAddress > 0xFF) CTLbyte |= (toAddress & 0x300) >> 6; //assign last 2 bits of address if > 255
    if (_address > 0xFF) CTLbyte |= (_address & 0x300) >> 8;   //assign last 2 bits of address if > 255
  
    // write to FIFO
    select();
    SPI.transfer(REG_FIFO | 0x80);
    SPI.transfer(bufferSize + 3);
    SPI.transfer((uint8_t)toAddress);
    SPI.transfer((uint8_t)_address);
    SPI.transfer(CTLbyte);
  
    for (uint8_t i = 0; i < bufferSize; i++)
      SPI.transfer(((uint8_t*) buffer)[i]);
    unselect();
  
    // no need to wait for transmit mode to be ready since its handled by the radio
    setMode(RF69_MODE_TX);
    uint32_t txStart = millis();
    while (digitalRead(_interruptPin) == 0 && millis() - txStart < RF69_TX_LIMIT_MS); // wait for DIO0 to turn HIGH signalling transmission finish
    //while (readReg(REG_IRQFLAGS2) & RF_IRQFLAGS2_PACKETSENT == 0x00); // wait for ModeReady
    setMode(RF69_MODE_STANDBY);
  }
  
  // internal function - interrupt gets called when a packet is received
  void RFM69::interruptHandler() {
    if (_mode == RF69_MODE_RX && (readReg(REG_IRQFLAGS2) & RF_IRQFLAGS2_PAYLOADREADY))
    {
      setMode(RF69_MODE_STANDBY);
      select();
      SPI.transfer(REG_FIFO & 0x7F);
      PAYLOADLEN = SPI.transfer(0);
      PAYLOADLEN = PAYLOADLEN > 66 ? 66 : PAYLOADLEN; // precaution
      TARGETID = SPI.transfer(0);
      SENDERID = SPI.transfer(0);
      uint8_t CTLbyte = SPI.transfer(0);
      TARGETID |= (uint16_t(CTLbyte) & 0x0C) << 6; //10 bit address (most significant 2 bits stored in bits(2,3) of CTL byte
      SENDERID |= (uint16_t(CTLbyte) & 0x03) << 8; //10 bit address (most sifnigicant 2 bits stored in bits(0,1) of CTL byte
      if(!(_promiscuousMode || TARGETID == _address || TARGETID == RF69_BROADCAST_ADDR) // match this node's address, or broadcast address or anything in promiscuous mode
         || PAYLOADLEN < 3) // address situation could receive packets that are malformed and don't fit this libraries extra fields
      {
        PAYLOADLEN = 0;
        unselect();
        receiveBegin();
        return;
      }
  
      DATALEN = PAYLOADLEN - 3;
      ACK_RECEIVED = CTLbyte & RFM69_CTL_SENDACK; // extract ACK-received flag
      ACK_REQUESTED = CTLbyte & RFM69_CTL_REQACK; // extract ACK-requested flag
      interruptHook(CTLbyte);     // TWS: hook to derived class interrupt function
  
      for (uint8_t i = 0; i < DATALEN; i++)
        DATA[i] = SPI.transfer(0);
      if (DATALEN < RF69_MAX_DATA_LEN) DATA[DATALEN] = 0; // add null at end of string
      unselect();
      setMode(RF69_MODE_RX);
    }
    RSSI = readRSSI();
  }
  
  // internal function
  void RFM69::isr0() { _haveData = true; }
  
  // internal function
  void RFM69::receiveBegin() {
    DATALEN = 0;
    SENDERID = 0;
    TARGETID = 0;
    PAYLOADLEN = 0;
    ACK_REQUESTED = 0;
    ACK_RECEIVED = 0;
  #if defined(RF69_LISTENMODE_ENABLE)
    RF69_LISTEN_BURST_REMAINING_MS = 0;
  #endif
    RSSI = 0;
    if (readReg(REG_IRQFLAGS2) & RF_IRQFLAGS2_PAYLOADREADY)
      writeReg(REG_PACKETCONFIG2, (readReg(REG_PACKETCONFIG2) & 0xFB) | RF_PACKET2_RXRESTART); // avoid RX deadlocks
    writeReg(REG_DIOMAPPING1, RF_DIOMAPPING1_DIO0_01); // set DIO0 to "PAYLOADREADY" in receive mode
    setMode(RF69_MODE_RX);
  }
  
  // checks if a packet was received and/or puts transceiver in receive (ie RX or listen) mode
  bool RFM69::receiveDone() {
  //ATOMIC_BLOCK(ATOMIC_FORCEON)
  //{
    if (_haveData) {
    	_haveData = false;
    	interruptHandler();
    }
    if (_mode == RF69_MODE_RX && PAYLOADLEN > 0)
    {
      setMode(RF69_MODE_STANDBY); // enables interrupts
      return true;
    }
    else if (_mode == RF69_MODE_RX) // already in RX no payload yet
    {
      return false;
    }
    receiveBegin();
    return false;
  //}
  }
  
  // To enable encryption: radio.encrypt("ABCDEFGHIJKLMNOP");
  // To disable encryption: radio.encrypt(null) or radio.encrypt(0)
  // KEY HAS TO BE 16 bytes !!!
  void RFM69::encrypt(const char* key) {
  #if defined(RF69_LISTENMODE_ENABLE)
    _haveEncryptKey = key;
  #endif
    setMode(RF69_MODE_STANDBY);
    if (key != 0)
    {
  #if defined(RF69_LISTENMODE_ENABLE)
      memcpy(_encryptKey, key, 16);
  #endif
      select();
      SPI.transfer(REG_AESKEY1 | 0x80);
      for (uint8_t i = 0; i < 16; i++)
        SPI.transfer(key[i]);
      unselect();
    }
    writeReg(REG_PACKETCONFIG2, (readReg(REG_PACKETCONFIG2) & 0xFE) | (key ? 1 : 0));
  }
  
  // get the received signal strength indicator (RSSI)
  int16_t RFM69::readRSSI(bool forceTrigger) {
    int16_t rssi = 0;
    if (forceTrigger)
    {
      // RSSI trigger not needed if DAGC is in continuous mode
      writeReg(REG_RSSICONFIG, RF_RSSI_START);
      while ((readReg(REG_RSSICONFIG) & RF_RSSI_DONE) == 0x00); // wait for RSSI_Ready
    }
    rssi = -readReg(REG_RSSIVALUE);
    rssi >>= 1;
    return rssi;
  }
  
  uint8_t RFM69::readReg(uint8_t addr)
  {
    select();
    SPI.transfer(addr & 0x7F);
    uint8_t regval = SPI.transfer(0);
    unselect();
    return regval;
  }
  
  void RFM69::writeReg(uint8_t addr, uint8_t value)
  {
    select();
    SPI.transfer(addr | 0x80);
    SPI.transfer(value);
    unselect();
  }
  
  // select the RFM69 transceiver (save SPI settings, set CS low)
  void RFM69::select() {
  #if defined (SPCR) && defined (SPSR)
    // save current SPI settings
    _SPCR = SPCR;
    _SPSR = SPSR;
  #endif
  
  #ifdef SPI_HAS_TRANSACTION
    SPI.beginTransaction(_settings);
  #endif
  
    // set RFM69 SPI settings
    SPI.setDataMode(SPI_MODE0);
    SPI.setBitOrder(MSBFIRST);
  #ifdef __arm__
  	SPI.setClockDivider(SPI_CLOCK_DIV16);
  #else
    SPI.setClockDivider(SPI_CLOCK_DIV4); // decided to slow down from DIV2 after SPI stalling in some instances, especially visible on mega1284p when RFM69 and FLASH chip both present
  #endif
    digitalWrite(_slaveSelectPin, LOW);
  }
  
  // unselect the RFM69 transceiver (set CS high, restore SPI settings)
  void RFM69::unselect() {
    digitalWrite(_slaveSelectPin, HIGH);
  #ifdef SPI_HAS_TRANSACTION
    SPI.endTransaction();
  #endif  
    // restore SPI settings to what they were before talking to RFM69
  #if defined (SPCR) && defined (SPSR)
    SPCR = _SPCR;
    SPSR = _SPSR;
  #endif
  }
  
  // true  = disable filtering to capture all frames on network
  // false = enable node/broadcast filtering to capture only frames sent to this/broadcast address
  void RFM69::promiscuous(bool onOff) {
    _promiscuousMode = onOff;
    //writeReg(REG_PACKETCONFIG1, (readReg(REG_PACKETCONFIG1) & 0xF9) | (onOff ? RF_PACKET1_ADRSFILTERING_OFF : RF_PACKET1_ADRSFILTERING_NODEBROADCAST));
  }
  
  // for RFM69HW only: you must call setHighPower(true) after initialize() or else transmission won't work
  void RFM69::setHighPower(bool onOff) {
    _isRFM69HW = onOff;
    writeReg(REG_OCP, _isRFM69HW ? RF_OCP_OFF : RF_OCP_ON);
    if (_isRFM69HW) // turning ON
      writeReg(REG_PALEVEL, (readReg(REG_PALEVEL) & 0x1F) | RF_PALEVEL_PA1_ON | RF_PALEVEL_PA2_ON); // enable P1 & P2 amplifier stages
    else
      writeReg(REG_PALEVEL, RF_PALEVEL_PA0_ON | RF_PALEVEL_PA1_OFF | RF_PALEVEL_PA2_OFF | _powerLevel); // enable P0 only
  }
  
  // internal function
  void RFM69::setHighPowerRegs(bool onOff) {
    writeReg(REG_TESTPA1, onOff ? 0x5D : 0x55);
    writeReg(REG_TESTPA2, onOff ? 0x7C : 0x70);
  }
  
  // set the slave select (CS) pin 
  void RFM69::setCS(uint8_t newSPISlaveSelect) {
    _slaveSelectPin = newSPISlaveSelect;
    digitalWrite(_slaveSelectPin, HIGH);
    pinMode(_slaveSelectPin, OUTPUT);
  }
  
  //for debugging
  #define REGISTER_DETAIL 0
  #if REGISTER_DETAIL
  // SERIAL PRINT
  // replace Serial.print("string") with SerialPrint("string")
  #define SerialPrint(x) SerialPrint_P(PSTR(x))
  void SerialWrite ( uint8_t c ) {
      Serial.write ( c );
  }
  
  void SerialPrint_P(PGM_P str, void (*f)(uint8_t) = SerialWrite ) {
    for (uint8_t c; (c = pgm_read_byte(str)); str++) (*f)(c);
  }
  #endif
  
  void RFM69::readAllRegs()
  {
    uint8_t regVal;
  
  #if REGISTER_DETAIL 
    int capVal;
  
    //... State Variables for intelligent decoding
    uint8_t modeFSK = 0;
    int bitRate = 0;
    int freqDev = 0;
    long freqCenter = 0;
  #endif
    
    Serial.println("Address - HEX - BIN");
    for (uint8_t regAddr = 1; regAddr <= 0x4F; regAddr++)
    {
      select();
      SPI.transfer(regAddr & 0x7F); // send address + r/w bit
      regVal = SPI.transfer(0);
      unselect();
  
      Serial.print(regAddr, HEX);
      Serial.print(" - ");
      Serial.print(regVal,HEX);
      Serial.print(" - ");
      Serial.println(regVal,BIN);
  
  #if REGISTER_DETAIL 
      switch ( regAddr ) 
      {
          case 0x1 : {
              SerialPrint ( "Controls the automatic Sequencer ( see section 4.2 )\nSequencerOff : " );
              if ( 0x80 & regVal ) {
                  SerialPrint ( "1 -> Mode is forced by the user\n" );
              } else {
                  SerialPrint ( "0 -> Operating mode as selected with Mode bits in RegOpMode is automatically reached with the Sequencer\n" );
              }
              
              SerialPrint( "\nEnables Listen mode, should be enabled whilst in Standby mode:\nListenOn : " );
              if ( 0x40 & regVal ) {
                  SerialPrint ( "1 -> On\n" );
              } else {
                  SerialPrint ( "0 -> Off ( see section 4.3)\n" );
              }
              
              SerialPrint( "\nAborts Listen mode when set together with ListenOn=0 See section 4.3.4 for details (Always reads 0.)\n" );
              if ( 0x20 & regVal ) {
                  SerialPrint ( "ERROR - ListenAbort should NEVER return 1 this is a write only register\n" );
              }
              
              SerialPrint("\nTransceiver's operating modes:\nMode : ");
              capVal = (regVal >> 2) & 0x7;
              if ( capVal == 0b000 ) {
                  SerialPrint ( "000 -> Sleep mode (SLEEP)\n" );
              } else if ( capVal = 0b001 ) {
                  SerialPrint ( "001 -> Standby mode (STDBY)\n" );
              } else if ( capVal = 0b010 ) {
                  SerialPrint ( "010 -> Frequency Synthesizer mode (FS)\n" );
              } else if ( capVal = 0b011 ) {
                  SerialPrint ( "011 -> Transmitter mode (TX)\n" );
              } else if ( capVal = 0b100 ) {
                  SerialPrint ( "100 -> Receiver Mode (RX)\n" );
              } else {
                  Serial.print( capVal, BIN );
                  SerialPrint ( " -> RESERVED\n" );
              }
              SerialPrint ( "\n" );
              break;
          }
          
          case 0x2 : {
          
              SerialPrint("Data Processing mode:\nDataMode : ");
              capVal = (regVal >> 5) & 0x3;
              if ( capVal == 0b00 ) {
                  SerialPrint ( "00 -> Packet mode\n" );
              } else if ( capVal == 0b01 ) {
                  SerialPrint ( "01 -> reserved\n" );
              } else if ( capVal == 0b10 ) {
                  SerialPrint ( "10 -> Continuous mode with bit synchronizer\n" );
              } else if ( capVal == 0b11 ) {
                  SerialPrint ( "11 -> Continuous mode without bit synchronizer\n" );
              }
              
              SerialPrint("\nModulation scheme:\nModulation Type : ");
              capVal = (regVal >> 3) & 0x3;
              if ( capVal == 0b00 ) {
                  SerialPrint ( "00 -> FSK\n" );
                  modeFSK = 1;
              } else if ( capVal == 0b01 ) {
                  SerialPrint ( "01 -> OOK\n" );
              } else if ( capVal == 0b10 ) {
                  SerialPrint ( "10 -> reserved\n" );
              } else if ( capVal == 0b11 ) {
                  SerialPrint ( "11 -> reserved\n" );
              }
              
              SerialPrint("\nData shaping: ");
              if ( modeFSK ) {
                  SerialPrint( "in FSK:\n" );
              } else {
                  SerialPrint( "in OOK:\n" );
              }
              SerialPrint ("ModulationShaping : ");
              capVal = regVal & 0x3;
              if ( modeFSK ) {
                  if ( capVal == 0b00 ) {
                      SerialPrint ( "00 -> no shaping\n" );
                  } else if ( capVal == 0b01 ) {
                      SerialPrint ( "01 -> Gaussian filter, BT = 1.0\n" );
                  } else if ( capVal == 0b10 ) {
                      SerialPrint ( "10 -> Gaussian filter, BT = 0.5\n" );
                  } else if ( capVal == 0b11 ) {
                      SerialPrint ( "11 -> Gaussian filter, BT = 0.3\n" );
                  }
              } else {
                  if ( capVal == 0b00 ) {
                      SerialPrint ( "00 -> no shaping\n" );
                  } else if ( capVal == 0b01 ) {
                      SerialPrint ( "01 -> filtering with f(cutoff) = BR\n" );
                  } else if ( capVal == 0b10 ) {
                      SerialPrint ( "10 -> filtering with f(cutoff) = 2*BR\n" );
                  } else if ( capVal == 0b11 ) {
                      SerialPrint ( "ERROR - 11 is reserved\n" );
                  }
              }
              
              SerialPrint ( "\n" );
              break;
          }
          
          case 0x3 : {
              bitRate = (regVal << 8);
              break;
          }
          
          case 0x4 : {
              bitRate |= regVal;
              SerialPrint ( "Bit Rate (Chip Rate when Manchester encoding is enabled)\nBitRate : ");
              unsigned long val = 32UL * 1000UL * 1000UL / bitRate;
              Serial.println( val );
              SerialPrint( "\n" );
              break;
          }
          
          case 0x5 : {
              freqDev = ( (regVal & 0x3f) << 8 );
              break;
          }
          
          case 0x6 : {
              freqDev |= regVal;
              SerialPrint( "Frequency deviation\nFdev : " );
              unsigned long val = RF69_FSTEP * freqDev;
              Serial.println( val );
              SerialPrint ( "\n" );
              break;
          }
          
          case 0x7 : {
              unsigned long tempVal = regVal;
              freqCenter = ( tempVal << 16 );
              break;
          }
         
          case 0x8 : {
              unsigned long tempVal = regVal;
              freqCenter = freqCenter | ( tempVal << 8 );
              break;
          }
  
          case 0x9 : {        
              freqCenter = freqCenter | regVal;
              SerialPrint ( "RF Carrier frequency\nFRF : " );
              unsigned long val = RF69_FSTEP * freqCenter;
              Serial.println( val );
              SerialPrint( "\n" );
              break;
          }
  
          case 0xa : {
              SerialPrint ( "RC calibration control & status\nRcCalDone : " );
              if ( 0x40 & regVal ) {
                  SerialPrint ( "1 -> RC calibration is over\n" );
              } else {
                  SerialPrint ( "0 -> RC calibration is in progress\n" );
              }
          
              SerialPrint ( "\n" );
              break;
          }
  
          case 0xb : {
              SerialPrint ( "Improved AFC routine for signals with modulation index lower than 2.  Refer to section 3.4.16 for details\nAfcLowBetaOn : " );
              if ( 0x20 & regVal ) {
                  SerialPrint ( "1 -> Improved AFC routine\n" );
              } else {
                  SerialPrint ( "0 -> Standard AFC routine\n" );
              }
              SerialPrint ( "\n" );
              break;
          }
          
          case 0xc : {
              SerialPrint ( "Reserved\n\n" );
              break;
          }
  
          case 0xd : {
              byte val;
              SerialPrint ( "Resolution of Listen mode Idle time (calibrated RC osc):\nListenResolIdle : " );
              val = regVal >> 6;
              if ( val == 0b00 ) {
                  SerialPrint ( "00 -> reserved\n" );
              } else if ( val == 0b01 ) {
                  SerialPrint ( "01 -> 64 us\n" );
              } else if ( val == 0b10 ) {
                  SerialPrint ( "10 -> 4.1 ms\n" );
              } else if ( val == 0b11 ) {
                  SerialPrint ( "11 -> 262 ms\n" );
              }
              
              SerialPrint ( "\nResolution of Listen mode Rx time (calibrated RC osc):\nListenResolRx : " );
              val = (regVal >> 4) & 0x3;
              if ( val == 0b00 ) {
                  SerialPrint ( "00 -> reserved\n" );
              } else if ( val == 0b01 ) {
                  SerialPrint ( "01 -> 64 us\n" );
              } else if ( val == 0b10 ) {
                  SerialPrint ( "10 -> 4.1 ms\n" );
              } else if ( val == 0b11 ) {
                  SerialPrint ( "11 -> 262 ms\n" );
              }
  
              SerialPrint ( "\nCriteria for packet acceptance in Listen mode:\nListenCriteria : " );
              if ( 0x8 & regVal ) {
                  SerialPrint ( "1 -> signal strength is above RssiThreshold and SyncAddress matched\n" );
              } else {
                  SerialPrint ( "0 -> signal strength is above RssiThreshold\n" );
              }
              
              SerialPrint ( "\nAction taken after acceptance of a packet in Listen mode:\nListenEnd : " );
              val = (regVal >> 1 ) & 0x3;
              if ( val == 0b00 ) {
                  SerialPrint ( "00 -> chip stays in Rx mode. Listen mode stops and must be disabled (see section 4.3)\n" );
              } else if ( val == 0b01 ) {
                  SerialPrint ( "01 -> chip stays in Rx mode until PayloadReady or Timeout interrupt occurs.  It then goes to the mode defined by Mode. Listen mode stops and must be disabled (see section 4.3)\n" );
              } else if ( val == 0b10 ) {
                  SerialPrint ( "10 -> chip stays in Rx mode until PayloadReady or Timeout occurs.  Listen mode then resumes in Idle state.  FIFO content is lost at next Rx wakeup.\n" );
              } else if ( val == 0b11 ) {
                  SerialPrint ( "11 -> Reserved\n" );
              }
              
              
              SerialPrint ( "\n" );
              break;
          }
          
          default : {
          }
      }
  #endif
    }
    unselect();
  }
  
  void RFM69::readAllRegsCompact() {
    // Print the header row and first register entry
    Serial.println();Serial.print("     ");
    for ( uint8_t reg = 0x00; reg<0x10; reg++ ) {
      Serial.print(reg, HEX);
      Serial.print("  ");
    }
    Serial.println();
    Serial.print("00: -- ");
  
    // Loop over the registers from 0x01 to 0x7F and print their values
    for ( uint8_t reg = 0x01; reg<0x80; reg++ ) {
      if ( reg % 16 == 0 ) {    // Print the header column entries
        Serial.println();
        Serial.print( reg, HEX );
        Serial.print(": ");
      }
  
      // Print the actual register values
      uint8_t ret = readReg( reg );
      if ( ret < 0x10 ) Serial.print("0");  // Handle values less than 10
      Serial.print( ret, HEX);
      Serial.print(" ");
    }
  }
  
  uint8_t RFM69::readTemperature(uint8_t calFactor) // returns centigrade
  {
    setMode(RF69_MODE_STANDBY);
    writeReg(REG_TEMP1, RF_TEMP1_MEAS_START);
    while ((readReg(REG_TEMP1) & RF_TEMP1_MEAS_RUNNING));
    return ~readReg(REG_TEMP2) + COURSE_TEMP_COEF + calFactor; // 'complement' corrects the slope, rising temp = rising val
  } // COURSE_TEMP_COEF puts reading in the ballpark, user can add additional correction
  
  void RFM69::rcCalibration()
  {
    writeReg(REG_OSC1, RF_OSC1_RCCAL_START);
    while ((readReg(REG_OSC1) & RF_OSC1_RCCAL_DONE) == 0x00);
  }
  
  //=============================================================================
  //                     ListenMode specific functions  
  //=============================================================================
  #if defined(RF69_LISTENMODE_ENABLE)
  volatile uint16_t RFM69::RF69_LISTEN_BURST_REMAINING_MS = 0;
  
  //=============================================================================
  // reinitRadio() - use base class initialization with saved values
  //=============================================================================
  bool RFM69::reinitRadio()
  {
    if (!initialize(_freqBand, _address, _networkID)) return false;
    if (_haveEncryptKey) RFM69::encrypt(_encryptKey); // Restore the encryption key if necessary
    if (_isHighSpeed) writeReg(REG_LNA, (readReg(REG_LNA) & ~0x3) | RF_LNA_GAINSELECT_AUTO);
    return true;
  }
  
  static uint32_t getUsForResolution(uint8_t resolution)
  {
    switch (resolution) {
      case RF_LISTEN1_RESOL_RX_64:
      case RF_LISTEN1_RESOL_IDLE_64:
        return 64;
      case RF_LISTEN1_RESOL_RX_4100:
      case RF_LISTEN1_RESOL_IDLE_4100:
        return 4100;
      case RF_LISTEN1_RESOL_RX_262000:
      case RF_LISTEN1_RESOL_IDLE_262000:
        return 262000;
      default:
        // Whoops
        return 0;
    }
  }
  
  static uint32_t getCoefForResolution(uint8_t resolution, uint32_t duration)
  {
    uint32_t resolDuration = getUsForResolution(resolution);
    uint32_t result = duration / resolDuration;
  
    // If the next-higher coefficient is closer, use that
    if (abs(duration - ((result + 1) * resolDuration)) < abs(duration - (result * resolDuration)))
      return result + 1;
  
    return result;
  }
  
  static bool chooseResolutionAndCoef(uint8_t *resolutions, uint32_t duration, uint8_t& resolOut, uint8_t& coefOut)
  {
    for (int i = 0; resolutions[i]; i++) {
      uint32_t coef = getCoefForResolution(resolutions[i], duration);
      if (coef <= 255) {
        coefOut = coef;
        resolOut = resolutions[i];
        return true;
      }
    }
  
    // out of range
    return false;
  }
  
  bool RFM69::listenModeSetDurations(uint32_t& rxDuration, uint32_t& idleDuration)
  {
    uint8_t rxResolutions[] = { RF_LISTEN1_RESOL_RX_64, RF_LISTEN1_RESOL_RX_4100, RF_LISTEN1_RESOL_RX_262000, 0 };
    uint8_t idleResolutions[] = { RF_LISTEN1_RESOL_IDLE_64, RF_LISTEN1_RESOL_IDLE_4100, RF_LISTEN1_RESOL_IDLE_262000, 0 };
  
    if (!chooseResolutionAndCoef(rxResolutions, rxDuration, _rxListenResolution, _rxListenCoef))
      return false;
  
    if (!chooseResolutionAndCoef(idleResolutions, idleDuration, _idleListenResolution, _idleListenCoef))
      return false;
  
    rxDuration = getUsForResolution(_rxListenResolution) * _rxListenCoef;
    idleDuration = getUsForResolution(_idleListenResolution) * _idleListenCoef;
    _listenCycleDurationUs = rxDuration + idleDuration;
  
    return true;
  }
  
  void RFM69::listenModeGetDurations(uint32_t &rxDuration, uint32_t &idleDuration)
  {
    rxDuration = getUsForResolution(_rxListenResolution) * _rxListenCoef;
    idleDuration = getUsForResolution(_idleListenResolution) * _idleListenCoef;
  }
  
  void RFM69::listenModeReset(void)
  {
    DATALEN = 0;
    SENDERID = 0;
    TARGETID = 0;
    PAYLOADLEN = 0;
    ACK_REQUESTED = 0;
    ACK_RECEIVED = 0;
    RF69_LISTEN_BURST_REMAINING_MS = 0;
  }
  
  //=============================================================================
  // irq handler, simply calls listenModeInterruptHandler method so internal methods can be accessed easily
  //=============================================================================
  void RFM69::listenModeIrq() { selfPointer->listenModeInterruptHandler(); }
  
  //=============================================================================
  // listenModeInterruptHandler() - only called by listen irq handler
  //=============================================================================
  void RFM69::listenModeInterruptHandler(void)
  {
    if (DATALEN != 0) return;
  
    listenModeReset();
    noInterrupts();
    select();
  
    union                        // union to simplify addressing of long and short parts of time offset
    {
      uint32_t l;
      uint8_t  b[4];
    } burstRemaining;
  
    burstRemaining.l = 0;
  
    SPI.transfer(REG_FIFO & 0x7F);
    PAYLOADLEN = SPI.transfer(0);
    PAYLOADLEN = PAYLOADLEN > 64 ? 64 : PAYLOADLEN; // precaution
    TARGETID = SPI.transfer(0);
    if(!(_promiscuousMode || TARGETID == _address || TARGETID == RF69_BROADCAST_ADDR) // match this node's address, or broadcast address or anything in promiscuous mode
       || PAYLOADLEN < 3) // address situation could receive packets that are malformed and don't fit this library's extra fields
    {
      listenModeReset();
      goto out;
    }
  
    // We've read the target, and will read the sender id and two time offset bytes for a total of 4 bytes
    DATALEN = PAYLOADLEN - 4;
    SENDERID = SPI.transfer(0);
    burstRemaining.b[0] =  SPI.transfer(0);  // and get the time remaining
    burstRemaining.b[1] =  SPI.transfer(0);
    RF69_LISTEN_BURST_REMAINING_MS = burstRemaining.l;
  
    for (uint8_t i = 0; i < DATALEN; i++)
      DATA[i] = SPI.transfer(0);
  
    if (DATALEN < RF69_MAX_DATA_LEN)
      DATA[DATALEN] = 0; // add null at end of string
  
  out:
    unselect();
    interrupts();
  }
  
  //=============================================================================
  // listenModeStart() - switch radio to Listen Mode in prep for sleep until burst
  //=============================================================================
  void RFM69::listenModeStart(void)
  {
    //pRadio = this;
    while (readReg(REG_IRQFLAGS2) & RF_IRQFLAGS2_PACKETSENT == 0x00); // wait for ModeReady
    listenModeReset();
  
    detachInterrupt(_interruptNum);
    attachInterrupt(_interruptNum, listenModeIrq, RISING);
    setMode(RF69_MODE_STANDBY);
    writeReg(REG_DIOMAPPING1, RF_DIOMAPPING1_DIO0_01);
    writeReg(REG_FRFMSB, readReg(REG_FRFMSB) + 1);
    writeReg(REG_FRFLSB, readReg(REG_FRFLSB));      // MUST write to LSB to affect change!
  
    listenModeApplyHighSpeedSettings();
  
    writeReg(REG_PACKETCONFIG1, RF_PACKET1_FORMAT_VARIABLE | RF_PACKET1_DCFREE_WHITENING | RF_PACKET1_CRC_ON | RF_PACKET1_CRCAUTOCLEAR_ON);
    writeReg(REG_PACKETCONFIG2, RF_PACKET2_RXRESTARTDELAY_NONE | RF_PACKET2_AUTORXRESTART_ON | RF_PACKET2_AES_OFF);
    writeReg(REG_SYNCVALUE1, 0x5A);
    writeReg(REG_SYNCVALUE2, 0x5A);
    writeReg(REG_LISTEN1, _rxListenResolution | _idleListenResolution | RF_LISTEN1_CRITERIA_RSSI | RF_LISTEN1_END_10);
    writeReg(REG_LISTEN2, _idleListenCoef);
    writeReg(REG_LISTEN3, _rxListenCoef);
    writeReg(REG_RSSITHRESH, 180);
    writeReg(REG_RXTIMEOUT2, 75);
    writeReg(REG_OPMODE, RF_OPMODE_SEQUENCER_ON | RF_OPMODE_STANDBY);
    writeReg(REG_OPMODE, RF_OPMODE_SEQUENCER_ON | RF_OPMODE_LISTEN_ON  | RF_OPMODE_STANDBY);
  }
  
  //=============================================================================
  // listenModeEnd() - exit listen mode and reinit the radio
  //=============================================================================
  void RFM69::listenModeEnd(void)
  {
    detachInterrupt(_interruptNum);
    writeReg(REG_OPMODE, RF_OPMODE_SEQUENCER_ON | RF_OPMODE_LISTENABORT | RF_OPMODE_STANDBY);
    writeReg(REG_OPMODE, RF_OPMODE_SEQUENCER_ON | RF_OPMODE_STANDBY);
    writeReg(REG_RXTIMEOUT2, 0);
    setMode(RF69_MODE_STANDBY);
    while ((readReg(REG_IRQFLAGS1) & RF_IRQFLAGS1_MODEREADY) == 0x00); // wait for ModeReady
    listenModeReset();
    reinitRadio();
  }
  
  void RFM69::listenModeApplyHighSpeedSettings()
  {
    if (!_isHighSpeed) return;
    writeReg(REG_BITRATEMSB, RF_BITRATEMSB_200000);
    writeReg(REG_BITRATELSB, RF_BITRATELSB_200000);
    writeReg(REG_FDEVMSB, RF_FDEVMSB_100000);
    writeReg(REG_FDEVLSB, RF_FDEVLSB_100000);
    writeReg( REG_RXBW, RF_RXBW_DCCFREQ_000 | RF_RXBW_MANT_20 | RF_RXBW_EXP_0 );
    
    // Force LNA to the highest gain
    //writeReg(REG_LNA, (readReg(REG_LNA) << 2) | RF_LNA_GAINSELECT_MAX);
  }
  
  //=============================================================================
  // sendBurst() - send a burst of packets to a sleeping listening node (or all)
  //=============================================================================
  void RFM69::listenModeSendBurst( uint8_t targetNode, const void* buffer, uint8_t size )
  {
    detachInterrupt(_interruptNum);
    setMode(RF69_MODE_STANDBY);
    writeReg(REG_PACKETCONFIG1, RF_PACKET1_FORMAT_VARIABLE | RF_PACKET1_DCFREE_WHITENING | RF_PACKET1_CRC_ON | RF_PACKET1_CRCAUTOCLEAR_ON );
    writeReg(REG_PACKETCONFIG2, RF_PACKET2_RXRESTARTDELAY_NONE | RF_PACKET2_AUTORXRESTART_ON | RF_PACKET2_AES_OFF);
    writeReg(REG_SYNCVALUE1, 0x5A);
    writeReg(REG_SYNCVALUE2, 0x5A);
    listenModeApplyHighSpeedSettings();
    writeReg(REG_FRFMSB, readReg(REG_FRFMSB) + 1);
    writeReg(REG_FRFLSB, readReg(REG_FRFLSB));      // MUST write to LSB to affect change!
  
    union // union to simplify addressing of long and short parts of time offset
    {
      int32_t l;
      uint8_t b[4];
    } timeRemaining;
  
    uint16_t cycleDurationMs = _listenCycleDurationUs / 1000;
    timeRemaining.l = cycleDurationMs;
  
  #ifdef RF69_WL_DEBUG
    Serial.print("Sending burst for ");
    Serial.print(cycleDurationMs, DEC);
    Serial.println(" ms");
  #endif
  
    setMode(RF69_MODE_TX);
    uint32_t numSent = 0;
    uint32_t startTime = millis();
  
    while(timeRemaining.l > 0) {
      noInterrupts();
      // write to FIFO
      select();
      SPI.transfer(REG_FIFO | 0x80);
      SPI.transfer(size + 4);      // two bytes for target and sender node, two bytes for the burst time remaining
      SPI.transfer(targetNode);
      SPI.transfer(_address);
  
      // We send the burst time remaining with the packet so the receiver knows how long to wait before trying to reply
      SPI.transfer(timeRemaining.b[0]);
      SPI.transfer(timeRemaining.b[1]);
  
      for (uint8_t i = 0; i < size; i++) {
        SPI.transfer(((uint8_t*) buffer)[i]);
      }
  
      unselect();
      interrupts();
  
      while ((readReg(REG_IRQFLAGS2) & RF_IRQFLAGS2_FIFONOTEMPTY) != 0x00);  // make sure packet is sent before putting more into the FIFO
      timeRemaining.l = cycleDurationMs - (millis() - startTime);
    }
  
    setMode(RF69_MODE_STANDBY);
    reinitRadio();
  }
  #endif