RF24.cpp

/*
 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.



03/17/2013 : Charles-Henri Hallard (http://hallard.me)
             Modified to use with Arduipi board http://hallard.me/arduipi
						 Changed to use modified bcm2835 library

TMRh20 2014: Updated to work with optimized RF24 and RF24 Network Arduino libs.
*/

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


/****************************************************************************/
uint8_t RF24::read_register(uint8_t reg, uint8_t* buf, uint8_t len)
{
  uint8_t status;
	uint8_t * prx = spi_rxbuff;
	uint8_t * ptx = spi_txbuff;
  uint8_t size = len + 1; // Add register value to transmit buffer

	*ptx++ = ( R_REGISTER | ( REGISTER_MASK & reg ) );
	while (len--){
		*ptx++ = NOP ; // Dummy operation, just for reading
	}
  bcm2835_spi_transfernb( (char *) spi_txbuff, (char *) spi_rxbuff, size);

	status = *prx++; // status is 1st byte of receive buffer

	// decrement before to skip status byte
	while ( --size ){
		*buf++ = *prx++;
	}

  return status;
}

/****************************************************************************/
uint8_t RF24::read_register(uint8_t reg)
{
  uint8_t result;

	uint8_t * prx = spi_rxbuff;
	uint8_t * ptx = spi_txbuff;

	*ptx++ = ( R_REGISTER | ( REGISTER_MASK & reg ) );
	*ptx++ = NOP ; // Dummy operation, just for reading

  bcm2835_spi_transfernb( (char *) spi_txbuff, (char *) spi_rxbuff, 2);

	result = *++prx;   // result is 2nd byte of receive buffer

  return result;
}

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

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

	uint8_t * prx = spi_rxbuff;
	uint8_t * ptx = spi_txbuff;

	*ptx++ = ( W_REGISTER | ( REGISTER_MASK & reg ) );
	*ptx = value ;

  	bcm2835_spi_transfernb( (char *) spi_txbuff, (char *) spi_rxbuff, 2);

	status = *prx++; // status is 1st byte of receive buffer

  if (debug)
		printf("write_register(%02x,%02x)\r\n",reg,value);

  return status;
}

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

uint8_t RF24::write_register(uint8_t reg, const uint8_t* buf, uint8_t len)
{
  uint8_t status;
	uint8_t * prx = spi_rxbuff;
	uint8_t * ptx = spi_txbuff;
  uint8_t size = len + 1; // Add register value to transmit buffer

	*ptx++ = ( W_REGISTER | ( REGISTER_MASK & reg ) );
  while ( len-- )
    *ptx++ = *buf++;

  bcm2835_spi_transfernb( (char *) spi_txbuff, (char *) spi_rxbuff, size);

	status = *prx; // status is 1st byte of receive buffer

  return status;
}


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

uint8_t RF24::write_payload(const void* buf, uint8_t len, const uint8_t writeType)
{
  uint8_t status;
	uint8_t * prx = spi_rxbuff;
	uint8_t * ptx = spi_txbuff;
  uint8_t size ;

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

  uint8_t data_len = std::min(len,payload_size);
  uint8_t blank_len = dynamic_payloads_enabled ? 0 : payload_size - data_len;

	size = data_len + blank_len + 1 ; // Add register value to transmit buffer

  if (debug)
		printf("[Writing %u bytes %u blanks]",data_len,blank_len);

	*ptx++ =  W_TX_PAYLOAD;
  while ( data_len-- )
    *ptx++ =  *current++;
  while ( blank_len-- )
		*ptx++ =  0;

	bcm2835_spi_transfernb( (char *) spi_txbuff, (char *) spi_rxbuff, size);

	status = *prx; // status is 1st byte of receive buffer


  return status;
}

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

uint8_t RF24::read_payload(void* buf, uint8_t len)
{
  uint8_t status;
	uint8_t * prx = spi_rxbuff;
	uint8_t * ptx = spi_txbuff;
  uint8_t size ;

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

  uint8_t data_len = std::min(len,payload_size);
  uint8_t blank_len = dynamic_payloads_enabled ? 0 : payload_size - data_len;

	size = data_len + blank_len + 1; // Add register value to transmit buffer

  if (debug)
		printf("[Reading %u bytes %u blanks]",data_len,blank_len);

	*ptx++ =  R_RX_PAYLOAD;
	while(size--)
		*ptx++ = NOP;

	// Size has been lost during while, re affect
	size = data_len + blank_len + 1; // Add register value to transmit buffer

	bcm2835_spi_transfernb( (char *) spi_txbuff, (char *) spi_rxbuff, size);

	// 1st byte is status
	status = *prx++;

	// Decrement before to skip 1st status byte
  while ( --size )
    *current++ = *prx++;

  return status;
}

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

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

  status = bcm2835_spi_transfer( FLUSH_RX );

  return status;
}

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

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

  status = bcm2835_spi_transfer( FLUSH_TX );

  return status;
}

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

uint8_t RF24::get_status(void)
{
  return bcm2835_spi_transfer( NOP );
}

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

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) & 0b111),
           (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) & 0b1111,
           (value >> ARC_CNT) & 0b1111
          );
}

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

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

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

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

  while (qty--)
  {
    uint8_t buffer[addr_width];
    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(uint8_t _cepin, uint8_t _cspin, uint32_t _spi_speed):
  ce_pin(_cepin), csn_pin(_cspin), spi_speed(_spi_speed),p_variant(false),
  payload_size(32), dynamic_payloads_enabled(false),addr_width(5)//,pipe0_reading_address(0)
{
}

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

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

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

void RF24::setPayloadSize(uint8_t size)
{
  const uint8_t max_payload_size = 32;
  payload_size = std::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_HIGH";
static const char rf24_pa_dbm_e_str_3[] = "PA_MAX";
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,
};

static const char rf24_csn_e_str_0[] = "CE0 (PI Hardware Driven)";
static const char rf24_csn_e_str_1[] = "CE1 (PI Hardware Driven)";
static const char rf24_csn_e_str_2[] = "CE2 (PI Hardware Driven)";
static const char rf24_csn_e_str_3[] = "Custom GPIO Software Driven";
static const char * const rf24_csn_e_str_P[] = {
  rf24_csn_e_str_0,
  rf24_csn_e_str_1,
  rf24_csn_e_str_2,
  rf24_csn_e_str_3,
};

// Display NRF24L01 details
void RF24::printDetails(void)
{
	printf("================ SPI Configuration ================\n" );

	if (csn_pin < BCM2835_SPI_CS_NONE )
	{
		printf("CSN Pin  \t = %s\n",rf24_csn_e_str_P[csn_pin]);
	}
	else
	{
		printf("CSN Pin  \t = Custom GPIO%d%s\n", csn_pin,
			csn_pin==RPI_V2_GPIO_P1_26 ? " (CE1) Software Driven" : "" );
	}

  printf("CE Pin  \t = Custom GPIO%d\n", ce_pin );

	// SPI Bus Speed
	printf("Clock Speed\t = " );
	switch (spi_speed)
	{
		case BCM2835_SPI_SPEED_64MHZ : printf("64 Mhz");	break ;
		case BCM2835_SPI_SPEED_32MHZ : printf("32 Mhz");	break ;
		case BCM2835_SPI_SPEED_16MHZ : printf("16 Mhz");	break ;
		case BCM2835_SPI_SPEED_8MHZ  : printf("8 Mhz");	break ;
		case BCM2835_SPI_SPEED_4MHZ  : printf("4 Mhz");	break ;
		case BCM2835_SPI_SPEED_2MHZ  : printf("2 Mhz");	break ;
		case BCM2835_SPI_SPEED_1MHZ  : printf("1 Mhz");	break ;
		case BCM2835_SPI_SPEED_512KHZ: printf("512 KHz");	break ;
		case BCM2835_SPI_SPEED_256KHZ: printf("256 KHz");	break ;
		case BCM2835_SPI_SPEED_128KHZ: printf("128 KHz");	break ;
		case BCM2835_SPI_SPEED_64KHZ : printf("64 KHz");	break ;
		case BCM2835_SPI_SPEED_32KHZ : printf("32 KHz");	break ;
		case BCM2835_SPI_SPEED_16KHZ : printf("16 KHz");	break ;
		case BCM2835_SPI_SPEED_8KHZ  : printf("8 KHz");	break ;
		default : printf("Probably Bad !!!");	break ;
	}
	printf("\n");

	printf("================ NRF Configuration ================\n" );

  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()]);
}

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

bool RF24::begin(void)
{
	debug = false;
	#if defined(DEBUG)
	  debug = true;
    #endif
	// This initialize the SPI bus with
	// csn pin as chip select (custom or not)


	// Init BCM2835 chipset for talking with us
	if (!bcm2835_init()){
		return false;
	}

	switch(csn_pin){     //Ensure valid hardware CS pin
		case 0: break;
		case 1: break;
		case 8: csn_pin = 0; break;
		case 7: csn_pin = 1; break;
		default: csn_pin = 0; break;
	}


	bcm2835_spi_begin();

	// used to drive custom I/O to trigger my logic analyser
	// bcm2835_gpio_fsel(GPIO_CTRL_PIN , BCM2835_GPIO_FSEL_OUTP);

	// start the SPI library:
	// Note the NRF24 wants mode 0, MSB first and default to 1 Mbps
	bcm2835_spi_setBitOrder(BCM2835_SPI_BIT_ORDER_MSBFIRST);
	bcm2835_spi_setDataMode(BCM2835_SPI_MODE0);

	// Set SPI bus Speed
	bcm2835_spi_setClockDivider(spi_speed);

    // Choose hardware CSN pin
    bcm2835_spi_chipSelect(csn_pin);


	// Initialise the CE pin of NRF24 (chip enable) after the CSN pin, so that
	// The input mode is not changed if using one of the hardware CE pins
	bcm2835_gpio_fsel(ce_pin, BCM2835_GPIO_FSEL_OUTP);
 	bcm2835_gpio_write(ce_pin, LOW);

  // wait 100ms
  delay(100);

  // 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.
  //printf("write_register(%02X, %02X)\n", SETUP_RETR, (0b0100 << ARD) | (0b1111 << ARC));
  setRetries(5,15);

  // 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 ) ;

  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(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();

  // 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) );

  return true;
}

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

void RF24::startListening(void)
{
  powerUp();
  write_register(CONFIG, read_register(CONFIG) | _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[0] > 0){
    write_register(RX_ADDR_P0, pipe0_reading_address,addr_width);
  }
  // Flush buffers
  //flush_rx();
  flush_tx();

  // Go!
  bcm2835_gpio_write(ce_pin, HIGH);

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

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

void RF24::stopListening(void)
{
  bcm2835_gpio_write(ce_pin, LOW);
  flush_tx();
  flush_rx();
  delayMicroseconds(150);
  write_register(CONFIG, ( read_register(CONFIG) ) & ~_BV(PRIM_RX) );
  delayMicroseconds(150);
}

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

void RF24::powerDown(void)
{
  bcm2835_gpio_write(ce_pin, LOW);
  write_register(CONFIG,read_register(CONFIG) & ~_BV(PWR_UP));
}

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

void RF24::powerUp(void)
{
  bool up = read_register(CONFIG) & _BV(PWR_UP);

  if(! up ){
	write_register(CONFIG, ( read_register(CONFIG) | _BV(PWR_UP) ));
	delay(5);
  }


}

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

#if defined (FAILURE_HANDLING)
void RF24::errNotify(){
	if(debug){ printf("HARDWARE FAIL\n\r"); }
	failureDetect = true;
}
#endif
/******************************************************************/

bool RF24::write( const void* buf, uint8_t len, const bool multicast ){

  // Begin the write
  startFastWrite(buf,len, multicast);


	//Wait until complete or failed
	#if defined (FAILURE_HANDLING)
		uint32_t timer = millis();
	#endif
    // If this hangs, it ain't coming back, no sense in timing out
	while( ! ( get_status()  & ( _BV(TX_DS) | _BV(MAX_RT) ))) {
		#if defined (FAILURE_HANDLING)
			if(millis() - timer > 175){
				errNotify();
				return 0;
			}
		#endif
	}
	bcm2835_gpio_write(ce_pin, LOW);
	uint8_t status = write_register(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 = millis();							  //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(millis() - timer > timeout){ return 0; }		  //If this payload has exceeded the user-defined timeout, exit and return 0
		}
		#if defined (FAILURE_HANDLING)
			if(millis() - timer > (timeout+75) ){
				errNotify();
				return 0;
			}
		#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(STATUS,_BV(MAX_RT) );			  //Clear max retry flag
		//spiTrans( REUSE_TX_PL );
		bcm2835_spi_transfer( REUSE_TX_PL);
		bcm2835_gpio_write(ce_pin, LOW);										  //Re-Transfer packet
		bcm2835_gpio_write(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 = millis();
	#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(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(millis() - timer > 75 ){
				errNotify();
				return 0;
			}
		#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){ //TMRh20

	//write_payload( buf,len);
	write_payload( buf, len,multicast ? W_TX_PAYLOAD_NO_ACK : W_TX_PAYLOAD ) ;
	bcm2835_gpio_write(ce_pin, HIGH);

}

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

void RF24::startWrite( const void* buf, uint8_t len, const bool multicast )
{

  // Send the payload

  write_payload( buf, len,multicast ? W_TX_PAYLOAD_NO_ACK : W_TX_PAYLOAD ) ;
  bcm2835_gpio_write(ce_pin, HIGH);
  delayMicroseconds(10);
  bcm2835_gpio_write(ce_pin, LOW);
}

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

bool RF24::txStandBy(){
    #if defined (FAILURE_HANDLING)
		uint32_t timer = millis();
	#endif
	while( ! (read_register(FIFO_STATUS) & _BV(TX_EMPTY)) ){
		if( get_status() & _BV(MAX_RT)){
			write_register(STATUS,_BV(MAX_RT) );
			bcm2835_gpio_write(ce_pin, LOW);
			flush_tx();    //Non blocking, flush the data
			return 0;
		}
		#if defined (FAILURE_HANDLING)
			if( millis() - timer > 75){
				errNotify();
				return 0;
			}
		#endif
	}

	bcm2835_gpio_write(ce_pin, LOW);			   //Set STANDBY-I mode
	return 1;
}

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

bool RF24::txStandBy(uint32_t timeout){

	uint32_t start = millis();

	while( ! (read_register(FIFO_STATUS) & _BV(TX_EMPTY)) ){
		if( get_status() & _BV(MAX_RT)){
			write_register(STATUS,_BV(MAX_RT) );
				bcm2835_gpio_write(ce_pin, LOW);										  //Set re-transmit
				bcm2835_gpio_write(ce_pin, HIGH);
				if(millis() - start >= timeout){
					bcm2835_gpio_write(ce_pin, LOW);
					flush_tx();
					return 0;
				}
		}
		#if defined (FAILURE_HANDLING)
			if( millis() - start > (timeout+75)){
				errNotify();
				return 0;
			}
		#endif
	}
	bcm2835_gpio_write(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)
{
  spi_txbuff[0] = R_RX_PL_WID;
  spi_rxbuff[1] = 0xff;

  bcm2835_spi_transfernb( (char *) spi_txbuff, (char *) spi_rxbuff, 2);

  if(spi_rxbuff[1] > 32) { flush_rx(); return 0; }

  return spi_rxbuff[1];
}

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

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

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

bool RF24::available(uint8_t* pipe_num)
{
    //Check the FIFO buffer to see if data is waitng to be read
  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 ) & 0b111;
  	}
  	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(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(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);


  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,min(payload_size,max_payload_size));
  write_register(RX_PW_P0,payload_size);
}

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

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){
	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::toggle_features(void)
{
  bcm2835_spi_transfer( ACTIVATE );
  bcm2835_spi_transfer( 0x73 );
}

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

void RF24::enableDynamicPayloads(void)
{

    // So enable them and try again
    toggle_features();
    write_register(FEATURE,read_register(FEATURE) | _BV(EN_DPL) );

  if (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
  //


    // So enable them and try again
    toggle_features();
    write_register(FEATURE,read_register(FEATURE) | _BV(EN_ACK_PAY) | _BV(EN_DPL) );

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

  //
  // Enable dynamic payload on pipes 0 & 1
  //
  dynamic_payloads_enabled = true;
  write_register(DYNPD,read_register(DYNPD) | _BV(DPL_P1) | _BV(DPL_P0));
}

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

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

  if(debug){printf("FEATURE=%i\r\n",read_register(FEATURE));}


}

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

void RF24::writeAckPayload(uint8_t pipe, const void* buf, uint8_t len)
{

  uint8_t * ptx = spi_txbuff;
  uint8_t size ;

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

  uint8_t data_len = std::min(len,payload_size);

  size = data_len + 1 ; // Add register value to transmit buffer

  if (debug){
		printf("[Writing %u bytes]",data_len);
  }
	*ptx++ =  W_ACK_PAYLOAD | ( pipe & 0b111 );
  while ( data_len-- ){
    *ptx++ =  *current++;
  }
	bcm2835_spi_transfern( (char *) spi_txbuff, size);

}


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

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, 0b111111);
  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) & 0b11111000;

  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)) ;
  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 ) ;
  }
  else
  {
    // Set 2Mbs, RF_DR (RF_DR_HIGH) is set 1
    // Making it '01'
    if ( speed == RF24_2MBPS )
    {
      setup |= _BV(RF_DR_HIGH);
    }
  }
  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)) ;

  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);
}