File content as of revision 2:3bdf0d9bb71f:

/*
 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 "nRF24L01.h"
#include "RF24_config.h"
#include "RF24.h"

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

void RF24::csn(bool mode)
{
    csn_pin = mode;
    wait_us(5);
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
}

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

void RF24::ce(bool level)
{
  ce_pin = level;
  
}

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

  inline void RF24::beginTransaction() {
    csn_pin=LOW;
    
    
    
  }

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

  inline void RF24::endTransaction() {
    csn_pin=HIGH;
    
    
    
  }

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

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

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

  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  return status;
}

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

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

  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  return result;
}

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

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

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

  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  return status;
}

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

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

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


  beginTransaction();
  status = spi.write( W_REGISTER | ( REGISTER_MASK & reg ) );
  spi.write(value);
  endTransaction();


  
  
  
  
  
  
  
  
  
  
  
  
  return status;
}

/****************************************************************************/
uint8_t RF24::write_payload(const void* buf, uint8_t len, const uint8_t writeType)
{
  uint8_t status;
  const uint8_t* current = reinterpret_cast<const uint8_t*>(buf);

   uint8_t data_len = rf24_min(data_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);
  IF_SERIAL_DEBUG( printf("[Writing %u bytes %u blanks]\n",data_len,blank_len); );
  

  beginTransaction();
    status = spi.write( W_TX_PAYLOAD );
  while ( data_len-- )
    spi.write(*current++);
  while ( blank_len-- )
    spi.write(0);
  
  endTransaction();



  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  return status;
}

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

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

  if(data_len > payload_size) data_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);

  IF_SERIAL_DEBUG( printf("[Reading %u bytes %u blanks]\n",data_len,blank_len); );

  beginTransaction();
  status = spi.write( R_RX_PAYLOAD );
  while ( data_len-- )
    *current++ = spi.write(0xff);
  while ( blank_len-- )
    spi.write(0xff);
  endTransaction();

  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  return status;
}

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

uint8_t RF24::flush_rx(void)
{
  return spiTrans( FLUSH_RX );
}

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

uint8_t RF24::flush_tx(void)
{
  return spiTrans( FLUSH_TX );
}

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

uint8_t RF24::spiTrans(uint8_t cmd){

  uint8_t status;

  beginTransaction();
  status = spi.write( cmd );
  endTransaction();

  
  
  
  
  
  
  
  return status;
}

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

uint8_t RF24::get_status(void)
{
  return spiTrans(NOP);
}

/****************************************************************************/
#if !defined (MINIMAL)
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)
{
printf("%s =",name);
  while (qty--)
    printf_P(PSTR(" 0x%02x"),read_register(reg++));
  printf_P(PSTR("\r\n"));
  
  
  
  
  
  
}

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

void RF24::print_address_register(const char* name, uint8_t reg, uint8_t qty)
{
  printf_P(PSTR(PRIPSTR"\t ="),name);
 
  while (qty--)
  {
    uint8_t buffer[addr_width];
    read_register(reg++,buffer,sizeof buffer);

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

  printf_P(PSTR("\r\n"));
  
  
  
  
}
#endif
/****************************************************************************/
  
RF24::RF24(PinName mosi, PinName miso, PinName sck, PinName _cepin, PinName _csnpin):
  ce_pin(_cepin), csn_pin(_csnpin), p_variant(false), 
  payload_size(32), dynamic_payloads_enabled(false), addr_width(5), spi(mosi, miso, sck)
{
  pipe0_reading_address[0]=0;
  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
  
  DigitalOut  ce_pin(_cepin); /**< "Chip Enable" pin, activates the RX or TX role */
  DigitalOut  csn_pin(_csnpin); /**< SPI Chip select */
  
  wait_ms(100);
  
}








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

void RF24::setChannel(uint8_t channel)
{
  const uint8_t max_channel = 127;
  write_register(RF_CH,rf24_min(channel,max_channel));
}

uint8_t RF24::getChannel()
{
  return read_register(RF_CH);
}
/****************************************************************************/

void RF24::setPayloadSize(uint8_t size)
{
  payload_size = rf24_min(size,32);
}

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

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

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

#if !defined (MINIMAL)

static const char rf24_datarate_e_str_0[] PROGMEM = "1MBPS";
static const char rf24_datarate_e_str_1[] PROGMEM = "2MBPS";
static const char rf24_datarate_e_str_2[] PROGMEM = "250KBPS";
static const char * const rf24_datarate_e_str_P[] PROGMEM = {
  rf24_datarate_e_str_0,
  rf24_datarate_e_str_1,
  rf24_datarate_e_str_2,
};
static const char rf24_model_e_str_0[] PROGMEM = "nRF24L01";
static const char rf24_model_e_str_1[] PROGMEM = "nRF24L01+";
static const char * const rf24_model_e_str_P[] PROGMEM = {
  rf24_model_e_str_0,
  rf24_model_e_str_1,
};
static const char rf24_crclength_e_str_0[] PROGMEM = "Disabled";
static const char rf24_crclength_e_str_1[] PROGMEM = "8 bits";
static const char rf24_crclength_e_str_2[] PROGMEM = "16 bits" ;
static const char * const rf24_crclength_e_str_P[] PROGMEM = {
  rf24_crclength_e_str_0,
  rf24_crclength_e_str_1,
  rf24_crclength_e_str_2,
};
static const char rf24_pa_dbm_e_str_0[] PROGMEM = "PA_MIN";
static const char rf24_pa_dbm_e_str_1[] PROGMEM = "PA_LOW";
static const char rf24_pa_dbm_e_str_2[] PROGMEM = "PA_HIGH";
static const char rf24_pa_dbm_e_str_3[] PROGMEM = "PA_MAX";
static const char * const rf24_pa_dbm_e_str_P[] PROGMEM = {
  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(PSTR("RX_ADDR_P0-1"),RX_ADDR_P0,2);
  print_byte_register(PSTR("RX_ADDR_P2-5"),RX_ADDR_P2,4);
  print_address_register(PSTR("TX_ADDR\t"),TX_ADDR);

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

   printf_P(PSTR("Data Rate\t = "PRIPSTR"\r\n"),pgm_read_word(&rf24_datarate_e_str_P[getDataRate()]));
  printf_P(PSTR("Model\t\t = "PRIPSTR"\r\n"),pgm_read_word(&rf24_model_e_str_P[isPVariant()]));
  printf_P(PSTR("CRC Length\t = "PRIPSTR"\r\n"),pgm_read_word(&rf24_crclength_e_str_P[getCRCLength()]));
  printf_P(PSTR("PA Power\t = "PRIPSTR"\r\n"),  pgm_read_word(&rf24_pa_dbm_e_str_P[getPALevel()]));

}

#endif
/****************************************************************************/

bool RF24::begin(void)
{

  uint8_t setup=0;

  mainTimer.start();
 
  ce_pin=LOW;
  csn_pin=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: Delay is based on P-variant whereby non-P *may* require different timing.
  wait_ms( 5 ) ;

  // Reset CONFIG and enable 16-bit CRC.
  write_register( CONFIG, 12 ) ;

  // 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.
  setRetries(5,15);

  // Reset value is MAX
  setPALevel( RF24_PA_MAX ) ;

  // check for connected module and if this is a p nRF24l01 variant
  //
  if( setDataRate( RF24_250KBPS ) )
  {
    p_variant = true ;
  }
  /*setup = read_register(RF_SETUP);
  if( setup == 0b00001110 )     // register default for nRF24L01P
  {
    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 - Reset value is 0
  toggle_features();
  write_register(FEATURE,0 );
  write_register(DYNPD,0);

  // Reset current status
  // Notice reset and flush is the last thing we do
  write_register(NRF_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);

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

  powerUp(); //Power up by default when begin() is called

  // Enable PTX, do not write CE high so radio will remain in standby I mode ( 130us max to transition to RX or TX instead of 1500us from powerUp )
  // PTX should use only 22uA of power
  write_register(CONFIG, ( read_register(CONFIG) ) & ~_BV(PRIM_RX) );

  // if setup is 0 or ff then there was no response from module
  return ( setup != 0 && setup != 0xff );
}

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

void RF24::startListening(void)
{



  write_register(CONFIG, read_register(CONFIG) | _BV(PRIM_RX));
  write_register(NRF_STATUS, _BV(RX_DR) | _BV(TX_DS) | _BV(MAX_RT) );
  ce(true);
  // Restore the pipe0 adddress, if exists
  if (pipe0_reading_address[0] > 0){
    write_register(RX_ADDR_P0, pipe0_reading_address, addr_width);  
  }else{
    closeReadingPipe(0);
  }

  // Flush buffers
  //flush_rx();
  if(read_register(FEATURE) & _BV(EN_ACK_PAY)){
    flush_tx();
  }

  // Go!
  //delayMicroseconds(100);
}

/****************************************************************************/
static const uint8_t child_pipe_enable[] PROGMEM =
{
  ERX_P0, ERX_P1, ERX_P2, ERX_P3, ERX_P4, ERX_P5
};

void RF24::stopListening(void)
{  
  ce_pin=LOW;

  wait_us(txRxDelay);
  
  if(read_register(FEATURE) & _BV(EN_ACK_PAY)){
    wait_us(txRxDelay); //200
    flush_tx();
  }
  //flush_rx();
  write_register(CONFIG, ( read_register(CONFIG) ) & ~_BV(PRIM_RX) );
 

  
  
  
  
  
  
  write_register(EN_RXADDR,read_register(EN_RXADDR) | _BV(pgm_read_byte(&child_pipe_enable[0]))); // Enable RX on pipe0
  
  //delayMicroseconds(100);

}

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

void RF24::powerDown(void)
{
  ce(false); // Guarantee CE is low on powerDown
  write_register(CONFIG,read_register(CONFIG) & ~_BV(PWR_UP));
}

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

//Power up now. Radio will not power down unless instructed by MCU for config changes etc.
void RF24::powerUp(void)
{
   uint8_t cfg = read_register(CONFIG);

   // if not powered up then power up and wait for the radio to initialize
   if (!(cfg & _BV(PWR_UP))){
      write_register(CONFIG,read_register(CONFIG) | _BV(PWR_UP));

      // For nRF24L01+ to go from power down mode to TX or RX mode it must first pass through stand-by mode.
      // There must be a delay of Tpd2stby (see Table 16.) after the nRF24L01+ leaves power down mode before
      // the CEis set high. - Tpd2stby can be up to 5ms per the 1.0 datasheet
      wait_ms(5);
   }
}

/******************************************************************/
#if defined (FAILURE_HANDLING) 
void RF24::errNotify(){
    #if defined (SERIAL_DEBUG) 
      printf_P(PSTR("RF24 HARDWARE FAIL: Radio not responding, verify pin connections, wiring, etc.\r\n"));
    #endif
    #if defined (FAILURE_HANDLING)
    failureDetected = 1;
    #else
    wait_ms(5000);
    #endif
}
#endif
/******************************************************************/

//Similar to the previous write, clears the interrupt flags
bool RF24::write( const void* buf, uint8_t len, const bool multicast )
{
    //Start Writing
    startFastWrite(buf,len,multicast);

    //Wait until complete or failed
    #if defined (FAILURE_HANDLING) 
        uint32_t timer = mainTimer.read_ms();
    #endif 
    
    while( ! ( get_status()  & ( _BV(TX_DS) | _BV(MAX_RT) ))) { 
        #if defined (FAILURE_HANDLING)
            if(mainTimer.read_ms() - timer > 85){           
                errNotify();
                #if defined (FAILURE_HANDLING)
                  return 0;     
                #else
                  wait_ms(100);
                #endif
            }
        #endif
    }
    
    ce_pin=LOW;

    uint8_t status = write_register(NRF_STATUS,_BV(RX_DR) | _BV(TX_DS) | _BV(MAX_RT) );

  //Max retries exceeded
  if( status & _BV(MAX_RT)){
    flush_tx(); //Only going to be 1 packet int the FIFO at a time using this method, so just flush
    return 0;
  }
    //TX OK 1 or 0
  return 1;
}

bool RF24::write( const void* buf, uint8_t len ){
    return write(buf,len,0);
}
/****************************************************************************/

//For general use, the interrupt flags are not important to clear
bool RF24::writeBlocking( const void* buf, uint8_t len, uint32_t timeout )
{
    //Block until the FIFO is NOT full.
    //Keep track of the MAX retries and set auto-retry if seeing failures
    //This way the FIFO will fill up and allow blocking until packets go through
    //The radio will auto-clear everything in the FIFO as long as CE remains high

    uint32_t timer = mainTimer.read_ms();                             //Get the time that the payload transmission started

    while( ( get_status()  & ( _BV(TX_FULL) ))) {         //Blocking only if FIFO is full. This will loop and block until TX is successful or timeout

        if( get_status() & _BV(MAX_RT)){                      //If MAX Retries have been reached
            reUseTX();                                        //Set re-transmit and clear the MAX_RT interrupt flag
            if(mainTimer.read_ms() - timer > timeout){ return 0; }        //If this payload has exceeded the user-defined timeout, exit and return 0
        }
        #if defined (FAILURE_HANDLING) 
            if(mainTimer.read_ms() - timer > (timeout+85) ){            
                errNotify();
                #if defined (FAILURE_HANDLING)
                return 0;           
                #endif              
            }
        #endif

    }

    //Start Writing
    startFastWrite(buf,len,0);                                //Write the payload if a buffer is clear

    return 1;                                                 //Return 1 to indicate successful transmission
}

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

void RF24::reUseTX(){
        write_register(NRF_STATUS,_BV(MAX_RT) );              //Clear max retry flag
        spiTrans( REUSE_TX_PL );
        ce_pin=LOW;                                       //Re-Transfer packet
        ce_pin=HIGH;
}

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

bool RF24::writeFast( const void* buf, uint8_t len, const bool multicast )
{
    //Block until the FIFO is NOT full.
    //Keep track of the MAX retries and set auto-retry if seeing failures
    //Return 0 so the user can control the retrys and set a timer or failure counter if required
    //The radio will auto-clear everything in the FIFO as long as CE remains high

    #if defined (FAILURE_HANDLING) 
        uint32_t timer = mainTimer.read_ms();
    #endif
    
    while( ( get_status()  & ( _BV(TX_FULL) ))) {             //Blocking only if FIFO is full. This will loop and block until TX is successful or fail

        if( get_status() & _BV(MAX_RT)){
            //reUseTX();                                          //Set re-transmit
            write_register(NRF_STATUS,_BV(MAX_RT) );              //Clear max retry flag
            return 0;                                         //Return 0. The previous payload has been retransmitted
                                                              //From the user perspective, if you get a 0, just keep trying to send the same payload
        }
        #if defined (FAILURE_HANDLING) 
            if(mainTimer.read_ms() - timer > 85 ){          
                errNotify();
                #if defined (FAILURE_HANDLING)
                return 0;                           
                #endif
            }
        #endif
    }
             //Start Writing
    startFastWrite(buf,len,multicast);

    return 1;
}

bool RF24::writeFast( const void* buf, uint8_t len ){
    return writeFast(buf,len,0);
}

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

//Per the documentation, we want to set PTX Mode when not listening. Then all we do is write data and set CE high
//In this mode, if we can keep the FIFO buffers loaded, packets will transmit immediately (no 130us delay)
//Otherwise we enter Standby-II mode, which is still faster than standby mode
//Also, we remove the need to keep writing the config register over and over and delaying for 150 us each time if sending a stream of data

void RF24::startFastWrite( const void* buf, uint8_t len, const bool multicast, bool startTx){ //TMRh20

    //write_payload( buf,len);
    write_payload( buf, len,multicast ? W_TX_PAYLOAD_NO_ACK : W_TX_PAYLOAD ) ;
    if(startTx){
        ce_pin=HIGH;
    }

}

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

//Added the original startWrite back in so users can still use interrupts, ack payloads, etc
//Allows the library to pass all tests
void RF24::startWrite( const void* buf, uint8_t len, const bool multicast ){

  // Send the payload

  //write_payload( buf, len );
  write_payload( buf, len,multicast? W_TX_PAYLOAD_NO_ACK : W_TX_PAYLOAD ) ;
  ce_pin=HIGH;
  
    wait_us(10);
  
  ce_pin=LOW;


}

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

bool RF24::rxFifoFull(){
    return read_register(FIFO_STATUS) & _BV(RX_FULL);
}
/****************************************************************************/

bool RF24::txStandBy(){

    #if defined (FAILURE_HANDLING) 
        uint32_t timeout = mainTimer.read_ms();
    #endif
    while( ! (read_register(FIFO_STATUS) & _BV(TX_EMPTY)) ){
        if( get_status() & _BV(MAX_RT)){
            write_register(NRF_STATUS,_BV(MAX_RT) );
            ce_pin=LOW;
            flush_tx();    //Non blocking, flush the data
            return 0;
        }
        #if defined (FAILURE_HANDLING) 
            if( mainTimer.read_ms() - timeout > 85){
                errNotify();
                #if defined (FAILURE_HANDLING)
                return 0;   
                #endif
            }
        #endif
    }

    ce_pin=LOW;               //Set STANDBY-I mode
    return 1;
}

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

bool RF24::txStandBy(uint32_t timeout, bool startTx){

    if(startTx){
      stopListening();
      ce_pin=HIGH;
    }
    uint32_t start = mainTimer.read_ms();

    while( ! (read_register(FIFO_STATUS) & _BV(TX_EMPTY)) ){
        if( get_status() & _BV(MAX_RT)){
            write_register(NRF_STATUS,_BV(MAX_RT) );
                ce_pin=LOW;                                          //Set re-transmit
                ce_pin=HIGH;
                if(mainTimer.read_ms() - start >= timeout){
                    ce_pin=LOW;; flush_tx(); return 0;
                }
        }
        #if defined (FAILURE_HANDLING) 
            if( mainTimer.read_ms() - start > (timeout+85)){
                errNotify();
                #if defined (FAILURE_HANDLING)
                return 0;   
                #endif
            }
        #endif
    }

    
    ce_pin=LOW;                   //Set STANDBY-I mode
    return 1;

}

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

void RF24::maskIRQ(bool tx, bool fail, bool rx){

    write_register(CONFIG, ( read_register(CONFIG) ) | fail << MASK_MAX_RT | tx << MASK_TX_DS | rx << MASK_RX_DR  );
}

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

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

  
  
  
  
  
  
  
  
  beginTransaction();
  spi.write( R_RX_PL_WID );
  result = spi.write(0xff);
  endTransaction();

  
  if(result > 32) { flush_rx(); wait_ms(2); return 0; }
  return result;
}

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

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

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

bool RF24::available(uint8_t* pipe_num)
{
    if (!( read_register(FIFO_STATUS) & _BV(RX_EMPTY) )) {

        // If the caller wants the pipe number, include that
        if ( pipe_num ) {
            uint8_t status = get_status();
            *pipe_num = ( status >> RX_P_NO ) & 7;
        }
        return 1;
    }
    
    
    return 0;
    
    
}

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

void RF24::read( void* buf, uint8_t len ){

  // Fetch the payload
  read_payload( buf, len );

  //Clear the two possible interrupt flags with one command
  write_register(NRF_STATUS,_BV(RX_DR) | _BV(MAX_RT) | _BV(TX_DS) );

}

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

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(NRF_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), addr_width);
  write_register(TX_ADDR, reinterpret_cast<uint8_t*>(&value), addr_width);
  
  
  //const uint8_t max_payload_size = 32;
  //write_register(RX_PW_P0,rf24_min(payload_size,max_payload_size));
  write_register(RX_PW_P0,payload_size);
}

/****************************************************************************/
void RF24::openWritingPipe(const uint8_t *address)
{
  // 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,address, addr_width);
  write_register(TX_ADDR, address, addr_width);

  //const uint8_t max_payload_size = 32;
  //write_register(RX_PW_P0,rf24_min(payload_size,max_payload_size));
  write_register(RX_PW_P0,payload_size);
}

/****************************************************************************/
static const uint8_t child_pipe[] PROGMEM =
{
  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[] PROGMEM =
{
  RX_PW_P0, RX_PW_P1, RX_PW_P2, RX_PW_P3, RX_PW_P4, RX_PW_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){
    memcpy(pipe0_reading_address,&address,addr_width);
  }

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

    write_register(pgm_read_byte(&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(pgm_read_byte(&child_pipe_enable[child])));
  }
}

/****************************************************************************/
void RF24::setAddressWidth(uint8_t a_width){

    if(a_width -= 2){
        write_register(SETUP_AW,a_width%4);
        addr_width = (a_width%4) + 2;
    }

}

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

void RF24::openReadingPipe(uint8_t child, const uint8_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){
    memcpy(pipe0_reading_address,address,addr_width);
  }
  if (child <= 6)
  {
    // For pipes 2-5, only write the LSB
    if ( child < 2 ){
      write_register(pgm_read_byte(&child_pipe[child]), address, addr_width);
    }else{
      write_register(pgm_read_byte(&child_pipe[child]), address, 1);
    }
    write_register(pgm_read_byte(&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(pgm_read_byte(&child_pipe_enable[child])));

  }
}

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

void RF24::closeReadingPipe( uint8_t pipe )
{
  write_register(EN_RXADDR,read_register(EN_RXADDR) & ~_BV(pgm_read_byte(&child_pipe_enable[pipe])));
}

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

void RF24::toggle_features(void)
{
    beginTransaction();
    spi.write( ACTIVATE );
    spi.write( 0x73 );
    endTransaction();
    
    
    
    
    
    
    
    
    
}

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

void RF24::enableDynamicPayloads(void)
{
  // Enable dynamic payload throughout the system

    //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
  //

    //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));
  dynamic_payloads_enabled = true;
}

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

void RF24::enableDynamicAck(void){
  //
  // enable dynamic ack features
  //
    //toggle_features();
    write_register(FEATURE,read_register(FEATURE) | _BV(EN_DYN_ACK) );

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


}

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

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

  uint8_t data_len = rf24_min(len,32);

  beginTransaction();
  spi.write(W_ACK_PAYLOAD | ( pipe & 7 ) );

  while ( data_len-- )
    spi.write(*current++);
  endTransaction();

}

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

bool RF24::isAckPayloadAvailable(void)
{
  return ! (read_register(FIFO_STATUS) & _BV(RX_EMPTY));
}

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

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(uint8_t level)
{

  uint8_t setup = read_register(RF_SETUP) & 248;

  if(level > 3){                        // If invalid level, go to max PA
      level = (RF24_PA_MAX << 1) + 1;       // +1 to support the SI24R1 chip extra bit
  }else{
      level = (level << 1) + 1;         // Else set level as requested
  }


  write_register( RF_SETUP, setup |= level ) ;  // Write it to the chip
}

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

uint8_t RF24::getPALevel(void)
{

  return (read_register(RF_SETUP) & (_BV(RF_PWR_LOW) | _BV(RF_PWR_HIGH))) >> 1 ;
}

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

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
  setup &= ~(_BV(RF_DR_LOW) | _BV(RF_DR_HIGH)) ;
  

    txRxDelay=85;

  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'.
    setup |= _BV( RF_DR_LOW ) ;
    txRxDelay=155;
  }
  else
  {
    // Set 2Mbs, RF_DR (RF_DR_HIGH) is set 1
    // Making it '01'
    if ( speed == RF24_2MBPS )
    {
      setup |= _BV(RF_DR_HIGH);
      txRxDelay=65;
    }
  }
  write_register(RF_SETUP,setup);

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

  // switch uses RAM (evil!)
  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)) ;
  uint8_t AA = read_register(EN_AA);
  
  if ( config & _BV(EN_CRC ) || AA)
  {
    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);
}