File content as of revision 0:bb74812ac6bb:

/*
 Copyright (C) 2011 J. Coliz <maniacbug@ymail.com>

 This program is free software; you can redistribute it and/or
 modify it under the terms of the GNU General Public License
 version 2 as published by the Free Software Foundation.
 */

#include "RF24.h"

/****************************************************************************/

void RF24::csn(int mode)
{
  // Minimum ideal spi bus speed is 2x data rate
  // If we assume 2Mbs data rate and 16Mhz clock, a
  // divider of 4 is the minimum we want.
  // CLK:BUS 8Mhz:2Mhz, 16Mhz:4Mhz, or 20Mhz:5Mhz
//#ifdef ARDUINO
//  spi.setBitOrder(MSBFIRST);
//  spi.setDataMode(spi_MODE0);
//  spi.setClockDivider(spi_CLOCK_DIV4);
//#endif
//  digitalWrite(csn_pin,mode);
    csn_pin = mode;
    
}

/****************************************************************************/

void RF24::ce(int level)
{
  //digitalWrite(ce_pin,level);
  ce_pin = level;
}

/****************************************************************************/

uint8_t RF24::read_register(uint8_t reg, uint8_t* buf, uint8_t len)
{
  uint8_t status;

  csn(LOW);
  status = spi.write( R_REGISTER | ( REGISTER_MASK & reg ) );
  while ( len-- )
    *buf++ = spi.write(0xff);

  csn(HIGH);

  return status;
}

/****************************************************************************/

uint8_t RF24::read_register(uint8_t reg)
{
  csn(LOW);
  spi.write( R_REGISTER | ( REGISTER_MASK & reg ) );
  uint8_t result = spi.write(0xff);

  csn(HIGH);
  return result;
}

/****************************************************************************/

uint8_t RF24::write_register(uint8_t reg, const uint8_t* buf, uint8_t len)
{
  uint8_t status;

  csn(LOW);
  status = spi.write( W_REGISTER | ( REGISTER_MASK & reg ) );
  while ( len-- )
    spi.write(*buf++);

  csn(HIGH);

  return status;
}

/****************************************************************************/

uint8_t RF24::write_register(uint8_t reg, uint8_t value)
{
  uint8_t status;

//  IF_SERIAL_DEBUG(printf(("write_register(%02x,%02x)\r\n"),reg,value));

  csn(LOW);
  status = spi.write( W_REGISTER | ( REGISTER_MASK & reg ) );
  spi.write(value);
  csn(HIGH);

  return status;
}

/****************************************************************************/

uint8_t RF24::write_payload(const void* buf, uint8_t len)
{
  uint8_t status;

  const uint8_t* current = reinterpret_cast<const uint8_t*>(buf);

  uint8_t data_len = min(len,payload_size);
  uint8_t blank_len = dynamic_payloads_enabled ? 0 : payload_size - data_len;
  
  //printf("[Writing %u bytes %u blanks]",data_len,blank_len);
  
  csn(LOW);
  status = spi.write( W_TX_PAYLOAD );
  while ( data_len-- )
    spi.write(*current++);
  while ( blank_len-- )
    spi.write(0);
  csn(HIGH);

  return status;
}

/****************************************************************************/

uint8_t RF24::read_payload(void* buf, uint8_t len)
{
  uint8_t status;
  uint8_t* current = reinterpret_cast<uint8_t*>(buf);

  uint8_t data_len = min(len,payload_size);
  uint8_t blank_len = dynamic_payloads_enabled ? 0 : payload_size - data_len;
  
  //printf("[Reading %u bytes %u blanks]",data_len,blank_len);
  
  csn(LOW);
  status = spi.write( R_RX_PAYLOAD );
  while ( data_len-- )
    *current++ = spi.write(0xff);
  while ( blank_len-- )
    spi.write(0xff);
  csn(HIGH);

  return status;
}

/****************************************************************************/

uint8_t RF24::flush_rx(void)
{
  uint8_t status;

  csn(LOW);
  status = spi.write( FLUSH_RX );
  csn(HIGH);

  return status;
}

/****************************************************************************/

uint8_t RF24::flush_tx(void)
{
  uint8_t status;

  csn(LOW);
  status = spi.write( FLUSH_TX );
  csn(HIGH);

  return status;
}

/****************************************************************************/

uint8_t RF24::get_status(void)
{
  uint8_t status;

  csn(LOW);
  status = spi.write( NOP );
  csn(HIGH);

  return status;
}

/****************************************************************************/

void RF24::print_status(uint8_t status)
{
  printf(("STATUS\t\t = 0x%02x RX_DR=%x TX_DS=%x MAX_RT=%x RX_P_NO=%x TX_FULL=%x\r\n"),
           status,
           (status & _BV(RX_DR))?1:0,
           (status & _BV(TX_DS))?1:0,
           (status & _BV(MAX_RT))?1:0,
           ((status >> RX_P_NO) & 7),
           (status & _BV(TX_FULL))?1:0
          );
}

/****************************************************************************/

void RF24::print_observe_tx(uint8_t value)
{
  printf(("OBSERVE_TX=%02x: POLS_CNT=%x ARC_CNT=%x\r\n"),
           value,
           (value >> PLOS_CNT) & 15,
           (value >> ARC_CNT) & 15
          );
}

/****************************************************************************/

void RF24::print_byte_register(const char* name, uint8_t reg, uint8_t qty)
{
//  char extra_tab = strlen(name) < 8 ? '\t' : 0;
  printf("%s =",name);
  while (qty--)
    printf((" 0x%02x"),read_register(reg++));
  printf(("\r\n"));
}

/****************************************************************************/

void RF24::print_address_register(const char* name, uint8_t reg, uint8_t qty)
{
//  char extra_tab = strlen_P(name) < 8 ? '\t' : 0;
  printf("%s =",name);

  while (qty--)
  {
    uint8_t buffer[5];
    read_register(reg++,buffer,sizeof buffer);

    printf((" 0x"));
    uint8_t* bufptr = buffer + sizeof buffer;
    while( --bufptr >= buffer )
      printf(("%02x"),*bufptr);
  }

  printf(("\r\n"));
}

/****************************************************************************/

RF24::RF24(PinName mosi, PinName miso, PinName sck, PinName _csnpin, PinName _cepin):
  ce_pin(_cepin), csn_pin(_csnpin), wide_band(true), p_variant(false), 
  payload_size(32), ack_payload_available(false), dynamic_payloads_enabled(false),
  pipe0_reading_address(0), spi(mosi, miso, sck)
{
    spi.frequency(10000000/5);     // 2Mbit, 1/5th the maximum transfer rate for the spi bus
    spi.format(8,0);                                   // 8-bit, ClockPhase = 0, ClockPolarity = 0
    wait_ms(100);
}

/****************************************************************************/

void RF24::setChannel(uint8_t channel)
{
  // TODO: This method could take advantage of the 'wide_band' calculation
  // done in setChannel() to require certain channel spacing.

  const uint8_t max_channel = 127;
  write_register(RF_CH,min(channel,max_channel));
}

/****************************************************************************/

void RF24::setPayloadSize(uint8_t size)
{
  const uint8_t max_payload_size = 32;
  payload_size = min(size,max_payload_size);
}

/****************************************************************************/

uint8_t RF24::getPayloadSize(void)
{
  return payload_size;
}

/****************************************************************************/

static const char rf24_datarate_e_str_0[]  = "1MBPS";
static const char rf24_datarate_e_str_1[]  = "2MBPS";
static const char rf24_datarate_e_str_2[]  = "250KBPS";
static const char * const rf24_datarate_e_str_P[]  = {
  rf24_datarate_e_str_0,
  rf24_datarate_e_str_1,
  rf24_datarate_e_str_2,
};
static const char rf24_model_e_str_0[]  = "nRF24L01";
static const char rf24_model_e_str_1[]  = "nRF24L01+";
static const char * const rf24_model_e_str_P[]  = {
  rf24_model_e_str_0,
  rf24_model_e_str_1,
};
static const char rf24_crclength_e_str_0[]  = "Disabled";
static const char rf24_crclength_e_str_1[]  = "8 bits";
static const char rf24_crclength_e_str_2[]  = "16 bits" ;
static const char * const rf24_crclength_e_str_P[]  = {
  rf24_crclength_e_str_0,
  rf24_crclength_e_str_1,
  rf24_crclength_e_str_2,
};
static const char rf24_pa_dbm_e_str_0[]  = "PA_MIN";
static const char rf24_pa_dbm_e_str_1[]  = "PA_LOW";
static const char rf24_pa_dbm_e_str_2[]  = "PA_MED";
static const char rf24_pa_dbm_e_str_3[]  = "PA_HIGH";
static const char * const rf24_pa_dbm_e_str_P[]  = { 
  rf24_pa_dbm_e_str_0,
  rf24_pa_dbm_e_str_1,
  rf24_pa_dbm_e_str_2,
  rf24_pa_dbm_e_str_3,
};

void RF24::printDetails(void)
{
  print_status(get_status());

  print_address_register(("RX_ADDR_P0-1"),RX_ADDR_P0,2);
  print_byte_register(("RX_ADDR_P2-5"),RX_ADDR_P2,4);
  print_address_register(("TX_ADDR"),TX_ADDR);

  print_byte_register(("RX_PW_P0-6"),RX_PW_P0,6);
  print_byte_register(("EN_AA"),EN_AA);
  print_byte_register(("EN_RXADDR"),EN_RXADDR);
  print_byte_register(("RF_CH"),RF_CH);
  print_byte_register(("RF_SETUP"),RF_SETUP);
  print_byte_register(("CONFIG"),CONFIG);
  print_byte_register(("DYNPD/FEATURE"),DYNPD,2);

  printf(("Data Rate\t = %s\r\n"), rf24_datarate_e_str_P[getDataRate()]);
  printf(("Model\t\t = %s\r\n"), rf24_model_e_str_P[isPVariant()]);
  printf(("CRC Length\t = %s\r\n"),rf24_crclength_e_str_P[getCRCLength()]);
  printf(("PA Power\t = %s\r\n"),rf24_pa_dbm_e_str_P[getPALevel()]);
}

/****************************************************************************/

void RF24::begin(void)
{
  // Initialize pins
//  pinMode(ce_pin,OUTPUT);
//  pinMode(csn_pin,OUTPUT);

  // Initialize spi bus
  //spi.begin();
  mainTimer.start();

  ce(LOW);
  csn(HIGH);

  // Must allow the radio time to settle else configuration bits will not necessarily stick.
  // This is actually only required following power up but some settling time also appears to
  // be required after resets too. For full coverage, we'll always assume the worst.
  // Enabling 16b CRC is by far the most obvious case if the wrong timing is used - or skipped.
  // Technically we require 4.5ms + 14us as a worst case. We'll just call it 5ms for good measure.
  // WARNING: wait_ms is based on P-variant whereby non-P *may* require different timing.
  wait_ms( 5 ) ;

  // Set 1500uS (minimum for 32B payload in ESB@250KBPS) timeouts, to make testing a little easier
  // WARNING: If this is ever lowered, either 250KBS mode with AA is broken or maximum packet
  // sizes must never be used. See documentation for a more complete explanation.
  write_register(SETUP_RETR,(4 << ARD) | (15 << ARC));

  // Restore our default PA level
  setPALevel( RF24_PA_MAX ) ;

  // Determine if this is a p or non-p RF24 module and then
  // reset our data rate back to default value. This works
  // because a non-P variant won't allow the data rate to
  // be set to 250Kbps.
  if( setDataRate( RF24_250KBPS ) )
  {
    p_variant = true ;
  }
  
  // Then set the data rate to the slowest (and most reliable) speed supported by all
  // hardware.
  setDataRate( RF24_1MBPS ) ;

  // Initialize CRC and request 2-byte (16bit) CRC
  setCRCLength( RF24_CRC_16 ) ;
  
  // Disable dynamic payloads, to match dynamic_payloads_enabled setting
  write_register(DYNPD,0);

  // Reset current status
  // Notice reset and flush is the last thing we do
  write_register(STATUS,_BV(RX_DR) | _BV(TX_DS) | _BV(MAX_RT) );

  // Set up default configuration.  Callers can always change it later.
  // This channel should be universally safe and not bleed over into adjacent
  // spectrum.
  //setChannel(76);
  setChannel(90);

  // Flush buffers
  flush_rx();
  flush_tx();
  
  // set EN_RXADDRR to 0 to fix pipe 0 from receiving
  write_register(EN_RXADDR, 0);
}

/****************************************************************************/

void RF24::startListening(void)
{
  write_register(CONFIG, read_register(CONFIG) | _BV(PWR_UP) | _BV(PRIM_RX));
  write_register(STATUS, _BV(RX_DR) | _BV(TX_DS) | _BV(MAX_RT) );

  // Restore the pipe0 adddress, if exists
  if (pipe0_reading_address)
    write_register(RX_ADDR_P0, reinterpret_cast<const uint8_t*>(&pipe0_reading_address), 5);

  // Flush buffers
  flush_rx();
  flush_tx();

  // Go!
  ce(HIGH);

  // wait for the radio to come up (130us actually only needed)
//  wait_msMicroseconds(130);
    wait_us(130);
}

/****************************************************************************/

void RF24::stopListening(void)
{
  ce(LOW);
  flush_tx();
  flush_rx();
}

/****************************************************************************/

void RF24::powerDown(void)
{
  write_register(CONFIG,read_register(CONFIG) & ~_BV(PWR_UP));
}

/****************************************************************************/

void RF24::powerUp(void)
{
  write_register(CONFIG,read_register(CONFIG) | _BV(PWR_UP));
}

/******************************************************************/

bool RF24::write( const void* buf, uint8_t len )
{
  bool result = false;

  // Begin the write
  startWrite(buf,len);

  // ------------
  // At this point we could return from a non-blocking write, and then call
  // the rest after an interrupt

  // Instead, we are going to block here until we get TX_DS (transmission completed and ack'd)
  // or MAX_RT (maximum retries, transmission failed).  Also, we'll timeout in case the radio
  // is flaky and we get neither.

  // IN the end, the send should be blocking.  It comes back in 60ms worst case, or much faster
  // if I tighted up the retry logic.  (Default settings will be 1500us.
  // Monitor the send
  uint8_t observe_tx;
  uint8_t status;
  uint32_t sent_at = mainTimer.read_ms();
  const uint32_t timeout = 500; //ms to wait for timeout
  do
  {
    status = read_register(OBSERVE_TX,&observe_tx,1);
//    IF_SERIAL_DEBUG(Serial.print(observe_tx,HEX));
  }
  while( ! ( status & ( _BV(TX_DS) | _BV(MAX_RT) ) ) && ( mainTimer.read_ms() - sent_at < timeout ) );

  // The part above is what you could recreate with your own interrupt handler,
  // and then call this when you got an interrupt
  // ------------

  // Call this when you get an interrupt
  // The status tells us three things
  // * The send was successful (TX_DS)
  // * The send failed, too many retries (MAX_RT)
  // * There is an ack packet waiting (RX_DR)
  bool tx_ok, tx_fail;
  whatHappened(tx_ok,tx_fail,ack_payload_available);
  
  //printf("%u%u%u\r\n",tx_ok,tx_fail,ack_payload_available);

  result = tx_ok;
//  IF_SERIAL_DEBUG(Serial.print(result?"...OK.":"...Failed"));

  // Handle the ack packet
  if ( ack_payload_available )
  {
    ack_payload_length = getDynamicPayloadSize();
//    IF_SERIAL_DEBUG(Serial.print("[AckPacket]/"));
//    IF_SERIAL_DEBUG(Serial.println(ack_payload_length,DEC));
  }

  // Yay, we are done.

  // Power down
//  powerDown();

  // Flush buffers (Is this a relic of past experimentation, and not needed anymore?
//  flush_tx();

  return result;
}
/****************************************************************************/

void RF24::startWrite( const void* buf, uint8_t len )
{
  // Transmitter power-up
  write_register(CONFIG, ( read_register(CONFIG) | _BV(PWR_UP) ) & ~_BV(PRIM_RX) );
//  wait_msMicroseconds(150);
    wait_us(130);

  // Send the payload
  write_payload( buf, len );

  // Allons!
  ce(HIGH);
//  wait_msMicroseconds(15);
    wait_us(15); 
  ce(LOW);
}

/****************************************************************************/

uint8_t RF24::getDynamicPayloadSize(void)
{
  uint8_t result = 0;

  csn(LOW);
  spi.write( R_RX_PL_WID );
  result = spi.write(0xff);
  csn(HIGH);

  return result;
}

/****************************************************************************/

bool RF24::available(void)
{
  return available(NULL);
}

/****************************************************************************/

bool RF24::available(uint8_t* pipe_num)
{
  uint8_t status = get_status();

  // Too noisy, enable if you really want lots o data!!
  //IF_SERIAL_DEBUG(print_status(status));

  bool result = ( status & _BV(RX_DR) );

  if (result)
  {
    // If the caller wants the pipe number, include that
    if ( pipe_num )
      *pipe_num = ( status >> RX_P_NO ) & 7;

    // Clear the status bit

    // ??? Should this REALLY be cleared now?  Or wait until we
    // actually READ the payload?

    write_register(STATUS,_BV(RX_DR) );

    // Handle ack payload receipt
    if ( status & _BV(TX_DS) )
    {
      write_register(STATUS,_BV(TX_DS));
    }
  }

  return result;
}

/****************************************************************************/

bool RF24::read( void* buf, uint8_t len )
{
  // Fetch the payload
  read_payload( buf, len );

  // was this the last of the data available?
  return read_register(FIFO_STATUS) & _BV(RX_EMPTY);
}

/****************************************************************************/

void RF24::whatHappened(bool& tx_ok,bool& tx_fail,bool& rx_ready)
{
  // Read the status & reset the status in one easy call
  // Or is that such a good idea?
  uint8_t status = write_register(STATUS,_BV(RX_DR) | _BV(TX_DS) | _BV(MAX_RT) );

  // Report to the user what happened
  tx_ok = status & _BV(TX_DS);
  tx_fail = status & _BV(MAX_RT);
  rx_ready = status & _BV(RX_DR);
}

/****************************************************************************/

void RF24::openWritingPipe(uint64_t value)
{
  // Note that AVR 8-bit uC's store this LSB first, and the NRF24L01(+)
  // expects it LSB first too, so we're good.

  write_register(RX_ADDR_P0, reinterpret_cast<uint8_t*>(&value), 5);
  write_register(TX_ADDR, reinterpret_cast<uint8_t*>(&value), 5);

  const uint8_t max_payload_size = 32;
  write_register(RX_PW_P0,min(payload_size,max_payload_size));
  
  flush_tx();
}

/****************************************************************************/

static const uint8_t child_pipe[]  =
{
  RX_ADDR_P0, RX_ADDR_P1, RX_ADDR_P2, RX_ADDR_P3, RX_ADDR_P4, RX_ADDR_P5
};
static const uint8_t child_payload_size[]  =
{
  RX_PW_P0, RX_PW_P1, RX_PW_P2, RX_PW_P3, RX_PW_P4, RX_PW_P5
};
static const uint8_t child_pipe_enable[]  =
{
  ERX_P0, ERX_P1, ERX_P2, ERX_P3, ERX_P4, ERX_P5
};

void RF24::openReadingPipe(uint8_t child, uint64_t address)
{
  // If this is pipe 0, cache the address.  This is needed because
  // openWritingPipe() will overwrite the pipe 0 address, so
  // startListening() will have to restore it.
  if (child == 0)
    pipe0_reading_address = address;

  if (child <= 6)
  {
    // For pipes 2-5, only write the LSB
    if ( child < 2 )
      write_register(child_pipe[child], reinterpret_cast<const uint8_t*>(&address), 5);
    else
      write_register(child_pipe[child], reinterpret_cast<const uint8_t*>(&address), 1);

    write_register(child_payload_size[child],payload_size);

    // Note it would be more efficient to set all of the bits for all open
    // pipes at once.  However, I thought it would make the calling code
    // more simple to do it this way.
    write_register(EN_RXADDR,read_register(EN_RXADDR) | _BV(child_pipe_enable[child]));
  }
}

/****************************************************************************/

void RF24::toggle_features(void)
{
  csn(LOW);
  spi.write( ACTIVATE );
  spi.write( 0x73 );
  csn(HIGH);
}

/****************************************************************************/

void RF24::enableDynamicPayloads(void)
{
  // Enable dynamic payload throughout the system
  write_register(FEATURE,read_register(FEATURE) | _BV(EN_DPL) );

  // If it didn't work, the features are not enabled
  if ( ! read_register(FEATURE) )
  {
    // So enable them and try again
    toggle_features();
    write_register(FEATURE,read_register(FEATURE) | _BV(EN_DPL) );
  }

//  IF_SERIAL_DEBUG(printf("FEATURE=%i\r\n",read_register(FEATURE)));

  // Enable dynamic payload on all pipes
  //
  // Not sure the use case of only having dynamic payload on certain
  // pipes, so the library does not support it.
  write_register(DYNPD,read_register(DYNPD) | _BV(DPL_P5) | _BV(DPL_P4) | _BV(DPL_P3) | _BV(DPL_P2) | _BV(DPL_P1) | _BV(DPL_P0));

  dynamic_payloads_enabled = true;
}

/****************************************************************************/

void RF24::enableAckPayload(void)
{
  //
  // enable ack payload and dynamic payload features
  //

  write_register(FEATURE,read_register(FEATURE) | _BV(EN_ACK_PAY) | _BV(EN_DPL) );

  // If it didn't work, the features are not enabled
  if ( ! read_register(FEATURE) )
  {
    // So enable them and try again
    toggle_features();
    write_register(FEATURE,read_register(FEATURE) | _BV(EN_ACK_PAY) | _BV(EN_DPL) );
  }

//  IF_SERIAL_DEBUG(printf("FEATURE=%i\r\n",read_register(FEATURE)));

  //
  // Enable dynamic payload on pipes 0 & 1
  //

  write_register(DYNPD,read_register(DYNPD) | _BV(DPL_P1) | _BV(DPL_P0));
}

/****************************************************************************/

void RF24::writeAckPayload(uint8_t pipe, const void* buf, uint8_t len)
{
  const uint8_t* current = reinterpret_cast<const uint8_t*>(buf);

  csn(LOW);
  spi.write( W_ACK_PAYLOAD | ( pipe & 7 ) );
  const uint8_t max_payload_size = 32;
  uint8_t data_len = min(len,max_payload_size);
  while ( data_len-- )
    spi.write(*current++);

  csn(HIGH);
}

/****************************************************************************/

bool RF24::isAckPayloadAvailable(void)
{
  bool result = ack_payload_available;
  ack_payload_available = false;
  return result;
}

/****************************************************************************/

bool RF24::isPVariant(void)
{
  return p_variant ;
}

/****************************************************************************/

void RF24::setAutoAck(bool enable)
{
  if ( enable )
    write_register(EN_AA, 63);
  else
    write_register(EN_AA, 0);
}

/****************************************************************************/

void RF24::setAutoAck( uint8_t pipe, bool enable )
{
  if ( pipe <= 6 )
  {
    uint8_t en_aa = read_register( EN_AA ) ;
    if( enable )
    {
      en_aa |= _BV(pipe) ;
    }
    else
    {
      en_aa &= ~_BV(pipe) ;
    }
    write_register( EN_AA, en_aa ) ;
  }
}

/****************************************************************************/

bool RF24::testCarrier(void)
{
  return ( read_register(CD) & 1 );
}

/****************************************************************************/

bool RF24::testRPD(void)
{
  return ( read_register(RPD) & 1 ) ;
}

/****************************************************************************/

void RF24::setPALevel(rf24_pa_dbm_e level)
{
  uint8_t setup = read_register(RF_SETUP) ;
  setup &= ~(_BV(RF_PWR_LOW) | _BV(RF_PWR_HIGH)) ;

  // switch uses RAM (evil!)
  if ( level == RF24_PA_MAX )
  {
    setup |= (_BV(RF_PWR_LOW) | _BV(RF_PWR_HIGH)) ;
  }
  else if ( level == RF24_PA_HIGH )
  {
    setup |= _BV(RF_PWR_HIGH) ;
  }
  else if ( level == RF24_PA_LOW )
  {
    setup |= _BV(RF_PWR_LOW);
  }
  else if ( level == RF24_PA_MIN )
  {
    // nothing
  }
  else if ( level == RF24_PA_ERROR )
  {
    // On error, go to maximum PA
    setup |= (_BV(RF_PWR_LOW) | _BV(RF_PWR_HIGH)) ;
  }

  write_register( RF_SETUP, setup ) ;
}

/****************************************************************************/

rf24_pa_dbm_e RF24::getPALevel(void)
{
  rf24_pa_dbm_e result = RF24_PA_ERROR ;
  uint8_t power = read_register(RF_SETUP) & (_BV(RF_PWR_LOW) | _BV(RF_PWR_HIGH)) ;

  // switch uses RAM (evil!)
  if ( power == (_BV(RF_PWR_LOW) | _BV(RF_PWR_HIGH)) )
  {
    result = RF24_PA_MAX ;
  }
  else if ( power == _BV(RF_PWR_HIGH) )
  {
    result = RF24_PA_HIGH ;
  }
  else if ( power == _BV(RF_PWR_LOW) )
  {
    result = RF24_PA_LOW ;
  }
  else
  {
    result = RF24_PA_MIN ;
  }

  return result ;
}

/****************************************************************************/

bool RF24::setDataRate(rf24_datarate_e speed)
{
  bool result = false;
  uint8_t setup = read_register(RF_SETUP) ;

  // HIGH and LOW '00' is 1Mbs - our default
  wide_band = false ;
  setup &= ~(_BV(RF_DR_LOW) | _BV(RF_DR_HIGH)) ;
  if( speed == RF24_250KBPS )
  {
    // Must set the RF_DR_LOW to 1; RF_DR_HIGH (used to be RF_DR) is already 0
    // Making it '10'.
    wide_band = false ;
    setup |= _BV( RF_DR_LOW ) ;
  }
  else
  {
    // Set 2Mbs, RF_DR (RF_DR_HIGH) is set 1
    // Making it '01'
    if ( speed == RF24_2MBPS )
    {
      wide_band = true ;
      setup |= _BV(RF_DR_HIGH);
    }
    else
    {
      // 1Mbs
      wide_band = false ;
    }
  }
  write_register(RF_SETUP,setup);

  // Verify our result
  if ( read_register(RF_SETUP) == setup )
  {
    result = true;
  }
  else
  {
    wide_band = false;
  }

  return result;
}

/****************************************************************************/

rf24_datarate_e RF24::getDataRate( void )
{
  rf24_datarate_e result ;
  uint8_t dr = read_register(RF_SETUP) & (_BV(RF_DR_LOW) | _BV(RF_DR_HIGH));
  
  // switch uses RAM (evil!)
  // Order matters in our case below
  if ( dr == _BV(RF_DR_LOW) )
  {
    // '10' = 250KBPS
    result = RF24_250KBPS ;
  }
  else if ( dr == _BV(RF_DR_HIGH) )
  {
    // '01' = 2MBPS
    result = RF24_2MBPS ;
  }
  else
  {
    // '00' = 1MBPS
    result = RF24_1MBPS ;
  }
  return result ;
}

/****************************************************************************/

void RF24::setCRCLength(rf24_crclength_e length)
{
  uint8_t config = read_register(CONFIG) & ~( _BV(CRCO) | _BV(EN_CRC)) ;
 
  if ( length == RF24_CRC_DISABLED )
  {
    // Do nothing, we turned it off above. 
  }
  else if ( length == RF24_CRC_8 )
  {
    config |= _BV(EN_CRC);
  }
  else
  {
    config |= _BV(EN_CRC);
    config |= _BV( CRCO );
  }
  write_register( CONFIG, config ) ;
}

/****************************************************************************/

rf24_crclength_e RF24::getCRCLength(void)
{
  rf24_crclength_e result = RF24_CRC_DISABLED;
  uint8_t config = read_register(CONFIG) & ( _BV(CRCO) | _BV(EN_CRC)) ;

  if ( config & _BV(EN_CRC ) )
  {
    if ( config & _BV(CRCO) )
      result = RF24_CRC_16;
    else
      result = RF24_CRC_8;
  }

  return result;
}

/****************************************************************************/

void RF24::disableCRC( void )
{
  uint8_t disable = read_register(CONFIG) & ~_BV(EN_CRC) ;
  write_register( CONFIG, disable ) ;
}

/****************************************************************************/
void RF24::setRetries(uint8_t delay, uint8_t count)
{
 write_register(SETUP_RETR,(delay&0xf)<<ARD | (count&0xf)<<ARC);
}

uint8_t RF24::min(uint8_t a, uint8_t b)
{
    if(a < b)
        return a;
    else
        return b;
}