RF24.h

/*
 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.
 */

/**
 * @file RF24.h
 *
 * Class declaration for RF24 and helper enums
 */

#ifndef __RF24_H__
#define __RF24_H__

#include <RF24_config.h>

/**
 * Power Amplifier level.
 *
 * For use with setPALevel()
 */
typedef enum { RF24_PA_MIN = 0,RF24_PA_LOW, RF24_PA_HIGH, RF24_PA_MAX, RF24_PA_ERROR } rf24_pa_dbm_e ;

/**
 * Data rate.  How fast data moves through the air.
 *
 * For use with setDataRate()
 */
typedef enum { RF24_1MBPS = 0, RF24_2MBPS, RF24_250KBPS } rf24_datarate_e;

/**
 * CRC Length.  How big (if any) of a CRC is included.
 *
 * For use with setCRCLength()
 */
typedef enum { RF24_CRC_DISABLED = 0, RF24_CRC_8, RF24_CRC_16 } rf24_crclength_e;

/**
 * Driver for nRF24L01(+) 2.4GHz Wireless Transceiver
 */

class RF24
{
private:
  uint8_t ce_pin; /**< "Chip Enable" pin, activates the RX or TX role */
  uint8_t csn_pin; /**< SPI Chip select */
  
  bool p_variant; /* False for RF24L01 and true for RF24L01P */
  uint8_t payload_size; /**< Fixed size of payloads */
  bool dynamic_payloads_enabled; /**< Whether dynamic payloads are enabled. */
  uint8_t pipe0_reading_address[5]; /**< Last address set on pipe 0 for reading. */
  uint8_t addr_width;
  

public:

  /**
   * @name Primary public interface
   *
   *  These are the main methods you need to operate the chip
   */
  /**@{*/

  /**
   * Constructor
   *
   * Creates a new instance of this driver.  Before using, you create an instance
   * and send in the unique pins that this chip is connected to.
   *
   * @param _cepin The pin attached to Chip Enable on the RF module
   * @param _cspin The pin attached to Chip Select
   */
  RF24(uint8_t _cepin, uint8_t _cspin);

  /**
   * Begin operation of the chip
   *
   * Call this in setup(), before calling any other methods.
   *
   * @note Optimization: The radio is partially configured in PTX mode
   * when begin is called to make the transition to PTX mode simpler.
   */
  void begin(void);

  /**
   * Start listening on the pipes opened for reading.
   *
   * Be sure to call openReadingPipe() first.  Do not call write() while
   * in this mode, without first calling stopListening().  Call
   * isAvailable() to check for incoming traffic, and read() to get it.
   */
  void startListening(void);

  /**
   * Stop listening for incoming messages
   *
   * Do this before calling write().
   *
   * @note Optimization: The radio will be taken out of PRX mode as soon
   * as listening is stopped. Enables quicker and simpler engaging of
   * primary transmitter (PTX) mode.
   */
  void stopListening(void);

  /**
   * Test whether there are bytes available to be read
   *
   * @note Optimization: The available functino now checks the FIFO
   * buffers directly for data instead of relying of interrupt flags.
   *
   * @note Interrupt flags will not be cleared until a payload is
   * actually read from the FIFO
   *
   * @see txStandBy()
   * @see startWrite()
   * @see write()
   * @see writeFast()
   *
   * @return True if there is a payload available, false if none is
   */
  bool available(void);

  /**
   * Read the payload
   *
   * The size of data read is the fixed payload size, see getPayloadSize()
   *
   * @note I specifically chose 'void*' as a data type to make it easier
   * for beginners to use.  No casting needed.
   *
   * @note Optimization: No longer boolean. Use available to
   * determine if packets are available. Interrupt flags are now cleared
   * during reads instead of when calling available().
   *
   * @param buf Pointer to a buffer where the data should be written
   * @param len Maximum number of bytes to read into the buffer
   * @return No return value. Use available().
   */
  void read( void* buf, uint8_t len );

  /**
   * @note Optimization: Improved performance slightly
   * Write to the open writing pipe
   *
   * Be sure to call openWritingPipe() first to set the destination
   * of where to write to.
   *
   * This blocks until the message is successfully acknowledged by
   * the receiver or the timeout/retransmit maxima are reached.  In
   * the current configuration, the max delay here is 60ms.
   *
   * The maximum size of data written is the fixed payload size, see
   * getPayloadSize().  However, you can write less, and the remainder
   * will just be filled with zeroes.
   *
   * TX/RX/RT interrupt flags will be cleared every time write is called
   *
   * @param buf Pointer to the data to be sent
   * @param len Number of bytes to be sent
   * @return True if the payload was delivered successfully false if not
   */
  bool write( const void* buf, uint8_t len );

  /**
   * New: Open a pipe for writing
   *
   * Only one pipe can be open at once, but you can change the pipe
   * you'll write to. Call stopListening() first.
   *
   * Addresses are assigned via a byte array, default is 5 byte address length
   *
   * Usage is exactly the same as before, except for declaring the array
   *
   * @code
   *   uint8_t addresses[][6] = {"1Node","2Node"};
   *   openWritingPipe(addresses[0]);
   * @endcode
   * @see setAddressWidth
   *
   * @param address The address of the pipe to open. Coordinate these pipe
   * addresses amongst nodes on the network.
   */

  void openWritingPipe(const uint8_t *address);

  /**
   * Open a pipe for reading
   *
   * Up to 6 pipes can be open for reading at once.  Open all the
   * reading pipes, and then call startListening().
   *
   * @see openWritingPipe
   * @see setAddressWidth
   *
   * @warning Pipes 1-5 should share the same address, except the first byte.
   * Only the first byte in the array should be unique, e.g.
   * @code
   *   uint8_t addresses[][6] = {"1Node","2Node"};
   *   openReadingPipe(1,addresses[0]);
   *   openReadingPipe(2,addresses[1]);
   * @endcode
   *
   * @warning Pipe 0 is also used by the writing pipe.  So if you open
   * pipe 0 for reading, and then startListening(), it will overwrite the
   * writing pipe.  Ergo, do an openWritingPipe() again before write().
   *
   * @param number Which pipe# to open, 0-5.
   * @param address The 24, 32 or 40 bit address of the pipe to open.
   */

  void openReadingPipe(uint8_t number, const uint8_t *address);

  /**
   * Close a pipe after it has been previously opened.
   * Can be safely called without having previously opened a pipe.
   * @param pipe Which pipe # to close, 0-5.
   */
  void closeReadingPipe( uint8_t pipe ) ;

  /**@}*/
  /**
   * @name Advanced Operation
   *
   *  Methods you can use to drive the chip in more advanced ways
   */
  /**@{*/

  /**
   * Print a giant block of debugging information to stdout
   *
   * @warning Does nothing if stdout is not defined.  See fdevopen in stdio.h
   */
  void printDetails(void);

  /**
   * Test whether there are bytes available to be read in the
   * FIFO buffers. This optimized version does not rely on interrupt
   * flags, but checks the actual FIFO buffers.
   *
   * @note Optimization: Interrupt flags are no longer cleared when available is called,
   * but will be reset only when the data is read from the FIFO buffers.
   *
   * @param[out] pipe_num Which pipe has the payload available
   * @return True if there is a payload available, false if none is
   */
  bool available(uint8_t* pipe_num);

  /**
   * Enter low-power mode
   *
   * To return to normal power mode, either write() some data or
   * startListening, or powerUp().
   *
   * @note Optimization: The radio will never enter power down unless instructed
   * by the MCU via this command.
   */
  void powerDown(void);

  /**
   * Leave low-power mode - making radio more responsive
   *
   * To return to low power mode, call powerDown().
   */
  void powerUp(void) ;

  /**
  * Write for single NOACK writes. Disables acknowledgements/autoretries for a single write.
  *
  * @note enableDynamicAck() must be called to enable this feature
  *
  * Can be used with enableAckPayload() to request a response
  * @see enableDynamicAck()
  * @see setAutoAck()
  * @see write()
  *
  * @param buf Pointer to the data to be sent
  * @param len Number of bytes to be sent
  * @param multicast Request ACK (0), NOACK (1)
  */
  bool write( const void* buf, uint8_t len, const bool multicast );

  /**
   * @note Optimization: New Command   *
   * This will not block until the 3 FIFO buffers are filled with data.
   * Once the FIFOs are full, writeFast will simply wait for success or
   * timeout, and return 1 or 0 respectively. From a user perspective, just
   * keep trying to send the same data. The library will keep auto retrying
   * the current payload using the built in functionality.
   * @warning It is important to never keep the nRF24L01 in TX mode for more than 4ms at a time. If the auto
   * retransmit is enabled, the nRF24L01 is never in TX mode long enough to disobey this rule. Allow the FIFO
   * to clear by issuing txStandBy() or ensure appropriate time between transmissions.
   *
   * ONLY max retry interrupt flags will be cleared when writeFast is called
   *
   * @code
   * Example (Partial blocking):
   *
   *			radio.writeFast(&buf,32);  // Writes 1 payload to the buffers
   *			txStandBy();     		   // Returns 0 if failed. 1 if success. Blocks only until MAX_RT timeout or success. Data flushed on fail.
   *
   *			radio.writeFast(&buf,32);  // Writes 1 payload to the buffers
   *			txStandBy(1000);		   // Using extended timeouts, returns 1 if success. Retries failed payloads for 1 seconds before returning 0.
   * @endcode
   *
   * @see txStandBy()
   * @see write()
   * @see writeBlocking()
   *
   * @param buf Pointer to the data to be sent
   * @param len Number of bytes to be sent
   * @return True if the payload was delivered successfully false if not
   */
  bool writeFast( const void* buf, uint8_t len );

  /**
  * WriteFast for single NOACK writes. Disables acknowledgements/autoretries for a single write.
  *
  * @note enableDynamicAck() must be called to enable this feature
  * @see enableDynamicAck()
  * @see setAutoAck()
  *
  * @param buf Pointer to the data to be sent
  * @param len Number of bytes to be sent
  * @param multicast Request ACK (0) or NOACK (1)
  */
  bool writeFast( const void* buf, uint8_t len, const bool multicast );

  /**
   * @note Optimization: New Command
   * This function extends the auto-retry mechanism to any specified duration.
   * It will not block until the 3 FIFO buffers are filled with data.
   * If so the library will auto retry until a new payload is written
   * or the user specified timeout period is reached.
   * @warning It is important to never keep the nRF24L01 in TX mode for more than 4ms at a time. If the auto
   * retransmit is enabled, the nRF24L01 is never in TX mode long enough to disobey this rule. Allow the FIFO
   * to clear by issuing txStandBy() or ensure appropriate time between transmissions.
   *
   * ONLY max retry interrupt flags will be cleared when writeBlocking is called
   * @code
   * Example (Full blocking):
   *
   *			radio.writeBlocking(&buf,32,1000); //Wait up to 1 second to write 1 payload to the buffers
   *			txStandBy(1000);     			   //Wait up to 1 second for the payload to send. Return 1 if ok, 0 if failed.
   *					  				   		   //Blocks only until user timeout or success. Data flushed on fail.
   * @endcode
   * @note If used from within an interrupt, the interrupt should be disabled until completion, and sei(); called to enable millis().
   * @see txStandBy()
   * @see write()
   * @see writeFast()
   *
   * @param buf Pointer to the data to be sent
   * @param len Number of bytes to be sent
   * @param timeout User defined timeout in milliseconds.
   * @return True if the payload was loaded into the buffer successfully false if not
   */
  bool writeBlocking( const void* buf, uint8_t len, uint32_t timeout );

  /**
   * @note Optimization: New Command
   * This function should be called as soon as transmission is finished to
   * drop the radio back to STANDBY-I mode. If not issued, the radio will
   * remain in STANDBY-II mode which, per the data sheet, is not a recommended
   * operating mode.
   *
   * @note When transmitting data in rapid succession, it is still recommended by
   * the manufacturer to drop the radio out of TX or STANDBY-II mode if there is
   * time enough between sends for the FIFOs to empty.
   *
   * Relies on built-in auto retry functionality.
   *
   * @code
   * Example (Partial blocking):
   *
   *			radio.writeFast(&buf,32);
   *			radio.writeFast(&buf,32);
   *			radio.writeFast(&buf,32);  //Fills the FIFO buffers up
   *			bool ok = txStandBy();     //Returns 0 if failed. 1 if success.
   *					  				   //Blocks only until MAX_RT timeout or success. Data flushed on fail.
   * @endcode
   * @see txStandBy(unsigned long timeout)
   * @return True if transmission is successful
   *
   */
   bool txStandBy();

  /**
   * @note Optimization: New Command
   *
   * This function allows extended blocking and auto-retries per a user defined timeout
   * @code
   *	Fully Blocking Example:
   *
   *			radio.writeFast(&buf,32);
   *			radio.writeFast(&buf,32);
   *			radio.writeFast(&buf,32);   //Fills the FIFO buffers up
   *			bool ok = txStandBy(1000);  //Returns 0 if failed after 1 second of retries. 1 if success.
   *					  				    //Blocks only until user defined timeout or success. Data flushed on fail.
   * @endcode
   * @note If used from within an interrupt, the interrupt should be disabled until completion, and sei(); called to enable millis().
   * @param timeout Number of milliseconds to retry failed payloads
   * @return True if transmission is successful
   *
   */
   bool txStandBy(uint32_t timeout);

  /**
   * Write an ack payload for the specified pipe
   *
   * The next time a message is received on @p pipe, the data in @p buf will
   * be sent back in the acknowledgement.
   *
   * @warning According to the data sheet, only three of these can be pending
   * at any time as there are only 3 FIFO buffers.
   *
   * @param pipe Which pipe# (typically 1-5) will get this response.
   * @param buf Pointer to data that is sent
   * @param len Length of the data to send, up to 32 bytes max.  Not affected
   * by the static payload set by setPayloadSize().
   */
  void writeAckPayload(uint8_t pipe, const void* buf, uint8_t len);

  /**
   * Enable dynamic ACKs (single write multicasting) for chosen messages
   *
   * @note To enable full multicasting or per-pipe multicast, use setAutoAck()
   *
   * @warning This MUST be called prior to attempting single write NOACK calls
   * @code
   * radio.enableDynamicAck();
   * radio.write(&data,32,1);  // Sends a payload with no acknowledgement requested
   * radio.write(&data,32,0);  // Sends a payload using auto-retry/autoACK
   * @endcode
   */
  void enableDynamicAck();

  /**
   * Determine if an ack payload was received in the most recent call to
   * write().
   *
   * Call read() to retrieve the ack payload.
   *
   * @note Optimization: Calling this function NO LONGER clears the interrupt
   * flag. The new functionality checks the RX FIFO buffer for an ACK payload
   * instead of relying on interrupt flags.Reading the payload will clear the flags.
   *
   * @return True if an ack payload is available.
   */
  bool isAckPayloadAvailable(void);

  /**
   * Call this when you get an interrupt to find out why
   *
   * Tells you what caused the interrupt, and clears the state of
   * interrupts.
   *
   * @param[out] tx_ok The send was successful (TX_DS)
   * @param[out] tx_fail The send failed, too many retries (MAX_RT)
   * @param[out] rx_ready There is a message waiting to be read (RX_DS)
   */
  void whatHappened(bool& tx_ok,bool& tx_fail,bool& rx_ready);

  /**
   * Non-blocking write to the open writing pipe used for buffered writes
   *
   * @note Optimization: This function now leaves the CE pin high, so the radio
   * will remain in TX or STANDBY-II Mode until a txStandBy() command is issued.
   * This allows the chip to be used to its full potential in TX mode.
   * @warning It is important to never keep the nRF24L01 in TX mode for more than 4ms at a time. If the auto
   * retransmit is enabled, the nRF24L01 is never in TX mode long enough to disobey this rule. Allow the FIFO
   * to clear by issuing txStandBy() or ensure appropriate time between transmissions.
   *
   * @see write()
   * @see writeFast()
   * @see startWrite()
   * @see writeBlocking()
   *
   * For single noAck writes see:
   * @see enableDynamicAck()
   * @see setAutoAck()
   *
   * @param buf Pointer to the data to be sent
   * @param len Number of bytes to be sent
   * @param multicast Request ACK (0) or NOACK (1)
   * @return True if the payload was delivered successfully false if not
   */
  void startFastWrite( const void* buf, uint8_t len, const bool multicast );

  /**
   * Non-blocking write to the open writing pipe
   *
   * Just like write(), but it returns immediately. To find out what happened
   * to the send, catch the IRQ and then call whatHappened().
   *
   * @note Optimization: This function again behaves as it did previously for backwards-compatibility.
   * with user code. The library uses startFastWrite() internally.
   * This is mainly used for single-payload transactions.
   *
   * @see write()
   * @see writeFast()
   * @see startFastWrite()
   * @see whatHappened()
   *
   * For single noAck writes see:
   * @see enableDynamicAck()
   * @see setAutoAck()
   *
   * @param buf Pointer to the data to be sent
   * @param len Number of bytes to be sent
   * @param multicast Request ACK (0) or NOACK (1)
   *
   */
  void startWrite( const void* buf, uint8_t len, const bool multicast );

  /**
   * Optimization: New Command
   *
   * This function is mainly used internally to take advantage of the auto payload
   * re-use functionality of the chip, but can be beneficial to users as well.
   *
   * The function will instruct the radio to re-use the data in the FIFO buffers,
   * and instructs the radio to re-send once the timeout limit has been reached.
   * Used by writeFast and writeBlocking to initiate retries when a TX failure
   * occurs. Retries are automatically initiated except with the standard write().
   * This way, data is not flushed from the buffer until switching between modes.
   *
   * @note This is to be used AFTER auto-retry fails if wanting to resend
   * using the built-in payload reuse features.
   * After issuing reUseTX(), it will keep reending the same payload forever or until
   * a payload is written to the FIFO, or a flush_tx command is given.
   */
   void reUseTX();

  /**
   * Empty the transmit buffer
   *
   * @return Current value of status register
   */
  uint8_t flush_tx(void);

  /**
   * Test whether there was a carrier on the line for the
   * previous listening period.
   *
   * Useful to check for interference on the current channel.
   *
   * @return true if was carrier, false if not
   */
  bool testCarrier(void);

  /**
   * Test whether a signal (carrier or otherwise) greater than
   * or equal to -64dBm is present on the channel. Valid only
   * on nRF24L01P (+) hardware. On nRF24L01, use testCarrier().
   *
   * Useful to check for interference on the current channel and
   * channel hopping strategies.
   *
   * @return true if signal => -64dBm, false if not
   */
  bool testRPD(void) ;

  /**
   * Test whether this is a real radio, or a mock shim for
   * debugging.  Setting either pin to 0xff is the way to
   * indicate that this is not a real radio.
   *
   * @return true if this is a legitimate radio
   */
  bool isValid() { return ce_pin != 0xff && csn_pin != 0xff; }

  /**
  * The radio will generate interrupt signals when a transmission is complete,
  * a transmission fails, or a payload is received. This allows users to mask
  * those interrupts to prevent them from generating a signal on the interrupt
  * pin.
  *
  * @code
  * 	Mask all interrupts except the receive interrupt:
  *
  *		radio.maskIRQ(1,1,0);
  * @endcode
  *
  * @param tx_ok  Mask transmission complete interrupts
  * @param tx_fail  Mask transmit failure interrupts
  * @param rx_ready Mask payload received interrupts
  */
  void maskIRQ(bool tx_ok,bool tx_fail,bool rx_ready);

  /**
  * Set the address width from 3 to 5 bytes (24, 32 or 40 bit)
  *
  * @param a_width The address width to use: 3,4 or 5
  */

  void setAddressWidth(uint8_t a_width);

  /**@}*/

  /**@}*/
  /**
   * @name Optional Configurators
   *
   *  Methods you can use to get or set the configuration of the chip.
   *  None are required.  Calling begin() sets up a reasonable set of
   *  defaults.
   */
  /**@{*/

  /**
   * Set the number and delay of retries upon failed submit
   *
   * @param delay How long to wait between each retry, in multiples of 250us,
   * max is 15.  0 means 250us, 15 means 4000us.
   * @param count How many retries before giving up, max 15
   */
  void setRetries(uint8_t delay, uint8_t count);

  /**
   * Set RF communication channel
   *
   * @param channel Which RF channel to communicate on, 0-127
   */
  void setChannel(uint8_t channel);

  /**
   * Set Static Payload Size
   *
   * This implementation uses a pre-stablished fixed payload size for all
   * transmissions.  If this method is never called, the driver will always
   * transmit the maximum payload size (32 bytes), no matter how much
   * was sent to write().
   *
   * @todo Implement variable-sized payloads feature
   *
   * @param size The number of bytes in the payload
   */
  void setPayloadSize(uint8_t size);

  /**
   * Get Static Payload Size
   *
   * @see setPayloadSize()
   *
   * @return The number of bytes in the payload
   */
  uint8_t getPayloadSize(void);

  /**
   * Get Dynamic Payload Size
   *
   * For dynamic payloads, this pulls the size of the payload off
   * the chip
   *
   * @note Optimization: Corrupt packets are now detected and flushed per the
   * manufacturer.
   *
   * @return Payload length of last-received dynamic payload
   */
  uint8_t getDynamicPayloadSize(void);

  /**
   * Enable custom payloads on the acknowledge packets
   *
   * Ack payloads are a handy way to return data back to senders without
   * manually changing the radio modes on both units.
   *
   * @see examples/pingpair_pl/pingpair_pl.pde
   */
  void enableAckPayload(void);

  /**
   * Enable dynamically-sized payloads
   *
   * This way you don't always have to send large packets just to send them
   * once in a while.  This enables dynamic payloads on ALL pipes.
   *
   * @see examples/pingpair_pl/pingpair_dyn.pde
   */
  void enableDynamicPayloads(void);

  /**
   * Determine whether the hardware is an nRF24L01+ or not.
   *
   * @return true if the hardware is nRF24L01+ (or compatible) and false
   * if its not.
   */
  bool isPVariant(void) ;

  /**
   * Enable or disable auto-acknowlede packets
   *
   * This is enabled by default, so it's only needed if you want to turn
   * it off for some reason.
   *
   * @param enable Whether to enable (true) or disable (false) auto-acks
   */
  void setAutoAck(bool enable);

  /**
   * Enable or disable auto-acknowlede packets on a per pipeline basis.
   *
   * AA is enabled by default, so it's only needed if you want to turn
   * it off/on for some reason on a per pipeline basis.
   *
   * @param pipe Which pipeline to modify
   * @param enable Whether to enable (true) or disable (false) auto-acks
   */
  void setAutoAck( uint8_t pipe, bool enable ) ;

  /**
   * Set Power Amplifier (PA) level to one of four levels:
   * RF24_PA_MIN, RF24_PA_LOW, RF24_PA_HIGH and RF24_PA_MAX
   *
   * The power levels correspond to the following output levels respectively:
   * NRF24L01: -18dBm, -12dBm,-6dBM, and 0dBm
   *
   * SI24R1: -6dBm, 0dBm, 3dBM, and 7dBm.
   *
   * @param level Desired PA level.
   */
  void setPALevel ( uint8_t level );

  /**
   * Fetches the current PA level.
   *
   * NRF24L01: -18dBm, -12dBm, -6dBm and 0dBm
   * SI24R1:   -6dBm, 0dBm, 3dBm, 7dBm
   *
   * @return Returns values 0 to 3 representing the PA Level.
   */
   uint8_t getPALevel( void );

  /**
   * Set the transmission data rate
   *
   * @warning setting RF24_250KBPS will fail for non-plus units
   *
   * @param speed RF24_250KBPS for 250kbs, RF24_1MBPS for 1Mbps, or RF24_2MBPS for 2Mbps
   * @return true if the change was successful
   */
  bool setDataRate(rf24_datarate_e speed);

  /**
   * Fetches the transmission data rate
   *
   * @return Returns the hardware's currently configured datarate. The value
   * is one of 250kbs, RF24_1MBPS for 1Mbps, or RF24_2MBPS, as defined in the
   * rf24_datarate_e enum.
   */
  rf24_datarate_e getDataRate( void ) ;

  /**
   * Set the CRC length
   *
   * @param length RF24_CRC_8 for 8-bit or RF24_CRC_16 for 16-bit
   */
  void setCRCLength(rf24_crclength_e length);

  /**
   * Get the CRC length
   *
   * @return RF24_DISABLED if disabled or RF24_CRC_8 for 8-bit or RF24_CRC_16 for 16-bit
   */
  rf24_crclength_e getCRCLength(void);

  /**
   * Disable CRC validation
   *
   */
  void disableCRC( void ) ;
  
   /**
   * Enable error detection by un-commenting #define FAILURE_HANDLING in RF24_config.h
   * If a failure has been detected, it usually indicates a hardware issue. By default the library
   * will cease operation when a failure is detected.  
   * This should allow advanced users to detect and resolve intermittent hardware issues.  
   *   
   * In most cases, the radio must be re-enabled via radio.begin(); and the appropriate settings
   * applied after a failure occurs, if wanting to re-enable the device immediately.
   * 
   * Usage: (Failure handling must be enabled per above)
   *  @code
   *  if(radio.failureDetected){ 
   *    radio.begin(); 					     // Attempt to re-configure the radio with defaults
   *    radio.failureDetected = 0;		     // Reset the detection value
   *	radio.openWritingPipe(addresses[1]); // Re-configure pipe addresses
    *   radio.openReadingPipe(1,addresses[0]);
   *    report_failure();               	 // Blink leds, send a message, etc. to indicate failure
   *  }
   * @endcode
  */
  #if defined (FAILURE_HANDLING)
    bool failureDetected; 
  #endif
  /**@}*/
  /**
   * @name Deprecated
   *
   *  Methods provided for backwards compabibility.
   */
  /**@{*/


  /**
   * Open a pipe for reading
   * @note For compatibility with old code only, see new function
   *
   * @warning Pipes 1-5 should share the first 32 bits.
   * Only the least significant byte should be unique, e.g.
   * @code
   *   openReadingPipe(1,0xF0F0F0F0AA);
   *   openReadingPipe(2,0xF0F0F0F066);
   * @endcode
   *
   * @warning Pipe 0 is also used by the writing pipe.  So if you open
   * pipe 0 for reading, and then startListening(), it will overwrite the
   * writing pipe.  Ergo, do an openWritingPipe() again before write().
   *
   * @param number Which pipe# to open, 0-5.
   * @param address The 40-bit address of the pipe to open.
   */
  void openReadingPipe(uint8_t number, uint64_t address);

  /**
   * Open a pipe for writing
   * @note For compatibility with old code only, see new function
   * Addresses are 40-bit hex values, e.g.:
   *
   * @code
   *   openWritingPipe(0xF0F0F0F0F0);
   * @endcode
   *
   * @param address The 40-bit address of the pipe to open.
   */
  void openWritingPipe(uint64_t address);

private:

  /**
   * @name Low-level internal interface.
   *
   *  Protected methods that address the chip directly.  Regular users cannot
   *  ever call these.  They are documented for completeness and for developers who
   *  may want to extend this class.
   */
  /**@{*/

  /**
   * Set chip select pin
   *
   * Running SPI bus at PI_CLOCK_DIV2 so we don't waste time transferring data
   * and best of all, we make use of the radio's FIFO buffers. A lower speed
   * means we're less likely to effectively leverage our FIFOs and pay a higher
   * AVR runtime cost as toll.
   *
   * @param mode HIGH to take this unit off the SPI bus, LOW to put it on
   */
  void csn(bool mode);

  /**
   * Set chip enable
   *
   * @param level HIGH to actively begin transmission or LOW to put in standby.  Please see data sheet
   * for a much more detailed description of this pin.
   */
  void ce(bool level);

  /**
   * Read a chunk of data in from a register
   *
   * @param reg Which register. Use constants from nRF24L01.h
   * @param buf Where to put the data
   * @param len How many bytes of data to transfer
   * @return Current value of status register
   */
  uint8_t read_register(uint8_t reg, uint8_t* buf, uint8_t len);

  /**
   * Read single byte from a register
   *
   * @param reg Which register. Use constants from nRF24L01.h
   * @return Current value of register @p reg
   */
  uint8_t read_register(uint8_t reg);

  /**
   * Write a chunk of data to a register
   *
   * @param reg Which register. Use constants from nRF24L01.h
   * @param buf Where to get the data
   * @param len How many bytes of data to transfer
   * @return Current value of status register
   */
  uint8_t write_register(uint8_t reg, const uint8_t* buf, uint8_t len);

  /**
   * Write a single byte to a register
   *
   * @param reg Which register. Use constants from nRF24L01.h
   * @param value The new value to write
   * @return Current value of status register
   */
  uint8_t write_register(uint8_t reg, uint8_t value);

  /**
   * Write the transmit payload
   *
   * The size of data written is the fixed payload size, see getPayloadSize()
   *
   * @param buf Where to get the data
   * @param len Number of bytes to be sent
   * @return Current value of status register
   */
  uint8_t write_payload(const void* buf, uint8_t len, const uint8_t writeType);

  /**
   * Read the receive payload
   *
   * The size of data read is the fixed payload size, see getPayloadSize()
   *
   * @param buf Where to put the data
   * @param len Maximum number of bytes to read
   * @return Current value of status register
   */
  uint8_t read_payload(void* buf, uint8_t len);

  /**
   * Empty the receive buffer
   *
   * @return Current value of status register
   */
  uint8_t flush_rx(void);

  /**
   * Retrieve the current status of the chip
   *
   * @return Current value of status register
   */
  uint8_t get_status(void);

  /**
   * Decode and print the given status to stdout
   *
   * @param status Status value to print
   *
   * @warning Does nothing if stdout is not defined.  See fdevopen in stdio.h
   */
  void print_status(uint8_t status);

  /**
   * Decode and print the given 'observe_tx' value to stdout
   *
   * @param value The observe_tx value to print
   *
   * @warning Does nothing if stdout is not defined.  See fdevopen in stdio.h
   */
  void print_observe_tx(uint8_t value);

  /**
   * Print the name and value of an 8-bit register to stdout
   *
   * Optionally it can print some quantity of successive
   * registers on the same line.  This is useful for printing a group
   * of related registers on one line.
   *
   * @param name Name of the register
   * @param reg Which register. Use constants from nRF24L01.h
   * @param qty How many successive registers to print
   */
  void print_byte_register(const char* name, uint8_t reg, uint8_t qty = 1);

  /**
   * Print the name and value of a 40-bit address register to stdout
   *
   * Optionally it can print some quantity of successive
   * registers on the same line.  This is useful for printing a group
   * of related registers on one line.
   *
   * @param name Name of the register
   * @param reg Which register. Use constants from nRF24L01.h
   * @param qty How many successive registers to print
   */
  void print_address_register(const char* name, uint8_t reg, uint8_t qty = 1);

  /**
   * Turn on or off the special features of the chip
   *
   * The chip has certain 'features' which are only available when the 'features'
   * are enabled.  See the datasheet for details.
   */
  void toggle_features(void);

  /**
   * Built in spi transfer function to simplify repeating code repeating code
   */

  uint8_t spiTrans(uint8_t cmd);
  
  #if defined (FAILURE_HANDLING)
	void errNotify(void);
  #endif
  
  /**@}*/

};

/**
 * @example GettingStarted.ino
 * <b>Updated: TMRh20 2014 </b><br>
 *
 * This is an example of how to use the RF24 class to communicate on a basic level.  Write this sketch to two
 * different nodes. Put one of the nodes into 'transmit' mode by connecting with the serial monitor and <br>
 * sending a 'T'. The ping node sends the current time to the pong node, which responds by sending the value
 * back. The ping node can then see how long the whole cycle took. <br>
 * @note For a more efficient call-response scenario see the GettingStarted_CallResponse.ino example.
 * @note When switching between sketches, the radio may need to be powered down to clear settings that are not "un-set" otherwise
 */

/**
 * @example GettingStarted_CallResponse.ino
 * <b>New: TMRh20 2014</b><br>
 *
 * This example continues to make use of all the normal functionality of the radios including
 * the auto-ack and auto-retry features, but allows ack-payloads to be written optionlly as well. <br>
 * This allows very fast call-response communication, with the responding radio never having to
 * switch out of Primary Receiver mode to send back a payload, but having the option to switch to <br>
 * primary transmitter if wanting to initiate communication instead of respond to a commmunication.
 */

/**
 * @example Transfer.ino
 * <b>New: TMRh20 </b><br>
 * This example demonstrates half-rate transfer using the FIFO buffers<br>
 *
 * It is an example of how to use the RF24 class.  Write this sketch to two
 * different nodes.  Put one of the nodes into 'transmit' mode by connecting <br>
 * with the serial monitor and sending a 'T'.  The data transfer will begin,
 * with the receiver displaying the payload count. (32Byte Payloads) <br>
 */

/**
 * @example TransferTimeouts.ino
 * <b>New: TMRh20 </b><br>
 * This example demonstrates the use of and extended timeout period and
 * auto-retries/auto-reUse to increase reliability in noisy or low signal scenarios. <br>
 *
 * Write this sketch to two different nodes.  Put one of the nodes into 'transmit'
 * mode by connecting with the serial monitor and sending a 'T'.  The data <br>
 * transfer will begin, with the receiver displaying the payload count and the
 * data transfer rate.
 */

/**
 * @example starping.pde
 *
 * This sketch is a more complex example of using the RF24 library for Arduino.
 * Deploy this on up to six nodes.  Set one as the 'pong receiver' by tying the
 * role_pin low, and the others will be 'ping transmit' units.  The ping units
 * unit will send out the value of millis() once a second.  The pong unit will
 * respond back with a copy of the value.  Each ping unit can get that response
 * back, and determine how long the whole cycle took.
 *
 * This example requires a bit more complexity to determine which unit is which.
 * The pong receiver is identified by having its role_pin tied to ground.
 * The ping senders are further differentiated by a byte in eeprom.
 */

/**
 * @example pingpair_ack.ino
 * <b>Update: TMRh20</b><br>
 * This example continues to make use of all the normal functionality of the radios including
 * the auto-ack and auto-retry features, but allows ack-payloads to be written optionlly as well.<br>
 * This allows very fast call-response communication, with the responding radio never having to
 * switch out of Primary Receiver mode to send back a payload, but having the option to if wanting<br>
 * to initiate communication instead of respond to a commmunication.
 */

/**
 * @example pingpair_irq.ino
 * <b>Update: TMRh20</b><br>
 * This is an example of how to user interrupts to interact with the radio, and a demonstration
 * of how to use them to sleep when receiving, and not miss any payloads.<br>
 * The pingpair_sleepy example expands on sleep functionality with a timed sleep option for the transmitter.
 * Sleep functionality is built directly into my fork of the RF24Network library<br>
 */

/**
 * @example pingpair_sleepy.ino
 * <b>Update: TMRh20</b><br>
 * This is an example of how to use the RF24 class to create a battery-
 * efficient system.  It is just like the GettingStarted_CallResponse example, but the<br>
 * ping node powers down the radio and sleeps the MCU after every
 * ping/pong cycle, and the receiver sleeps between payloads. <br>
 */

/**
 * @example pingpair_dyn.ino
 *
 * This is an example of how to use payloads of a varying (dynamic) size.
 */

/**
 * @example pingpair_maple.pde
 *
 * This is an example of how to use the RF24 class on the Maple.  For a more
 * detailed explanation, see my blog post:
 * <a href="http://maniacbug.wordpress.com/2011/12/14/nrf24l01-running-on-maple-3/">nRF24L01+ Running on Maple</a>
 *
 * It will communicate well to an Arduino-based unit as well, so it's not for only Maple-to-Maple communication.
 *
 * Write this sketch to two different nodes,
 * connect the role_pin to ground on one.  The ping node sends the current time to the pong node,
 * which responds by sending the value back.  The ping node can then see how long the whole cycle
 * took.
 */

/**
 * @example nordic_fob.pde
 *
 * This is an example of how to use the RF24 class to receive signals from the
 * Sparkfun Nordic FOB.  See http://www.sparkfun.com/products/8602 .
 * Thanks to Kirk Mower for providing test hardware.
 */

/**
 * @example led_remote.pde
 *
 * This is an example of how to use the RF24 class to control a remote
 * bank of LED's using buttons on a remote control.
 *
 * Every time the buttons change on the remote, the entire state of
 * buttons is send to the led board, which displays the state.
 */

/**
 * @example scanner.ino
 *
 * Example to detect interference on the various channels available.
 * This is a good diagnostic tool to check whether you're picking a
 * good channel for your application.
 *
 * Inspired by cpixip.
 * See http://arduino.cc/forum/index.php/topic,54795.0.html
 */

/**
 * @mainpage Optimized High Speed Driver for nRF24L01(+) 2.4GHz Wireless Transceiver
 *
 * @section Goals Design Goals
 *
 * This library fork is designed to be...
 * @li More compliant with the manufacturer specified operation of the chip, while allowing advanced users
 * to work outside the recommended operation.
 * @li Utilize the capabilities of the radio to their full potential via Arduino
 * @li More reliable, responsive and feature rich
 * @li Easy for beginners to use, with well documented examples and features
 * @li Consumed with a public interface that's similiar to other Arduino standard libraries
 *
 * @section News News
 *
 * <b>Main changes: </b><br>
 * - The library has been tweaked to allow full use of the FIFO buffers for maximum transfer speeds
 * - Changes to read() and available () functionality have increased reliability and response
 * - Extended timeout periods have been added to aid in noisy or otherwise unreliable environments
 * - Delays have been removed where possible to ensure maximum efficiency
 * - Full Due support with extended SPI functions
 * - ATTiny now supported.
 * - Raspberry Pi now supported
 * - More! See the links below and class documentation for more info.
 *
 * If issues are discovered with the documentation, please report them <a href="https://github.com/TMRh20/tmrh20.github.io/issues"> here</a>
 * @section Useful Useful References
 *
 * Please refer to:
 *
 * @li <a href="http://tmrh20.github.io/">Documentation Main Page</a>
 * @li <a href="http://tmrh20.github.io/RF24/classRF24.html">RF24 Class Documentation</a>
 * @li <a href="https://github.com/tmrh20/RF24/">Source Code</a>
 * @li <a href="https://github.com/TMRh20/RF24/archive/master.zip">Download</a>
 * @li <a href="http://www.nordicsemi.com/files/Product/data_sheet/nRF24L01_Product_Specification_v2_0.pdf">Chip Datasheet</a>
 * @li <a href="https://github.com/maniacbug/RF24">Original Library</a>
 *
 * This chip uses the SPI bus, plus two chip control pins.  Remember that pin 10 must still remain an output, or
 * the SPI hardware will go into 'slave' mode.
 *
 * @section Board_Support Board Support
 *
 * Most standard Arduino based boards are supported:
 * - ATMega 328 based boards (Uno, Nano, etc)
 * - Mega Boards (1280, 2560, etc)
 * - Arduino Due: Must use one of the hardware SS/CSN pins as extended SPI methods are used.
 *  Initial Due support taken from https://github.com/mcrosson/RF24/tree/due
 * - ATTiny board support added from https://github.com/jscrane/RF24
 * Note: ATTiny support is built into the library. Do not include SPI.h. <br>
 * ATTiny 85: D0(pin 5): MISO, D1(pin6) MOSI, D2(pin7) SCK, D3(pin2):CSN/SS, D4(pin3): CE <br>
 * ATTiny 84: PA6:MISO, PA5:MOSI, PA4:SCK, PA7:CSN/SS,  CE as desired <br>
 * See https://github.com/TCWORLD/ATTinyCore/tree/master/PCREL%20Patch%20for%20GCC for ATTiny patch
 * - Raspberry Pi Support: See the readme at https://github.com/TMRh20/RF24/tree/master/RPi
 *
 * @section More More Information
 *
 * @section Info and Projects
 *
 * @li Project blog:
 * @li <a href="http://TMRh20.blogspot.com"> TMRh20.blogspot.com </a>
 * @li <a href="http://tmrh20.github.io/RF24Audio/"> RF24 Wireless Audio Library </a>
 * @li <a href="https://github.com/TMRh20/RF24Network"> Optimized RF24 Network Layer </a>
 * @li <a href="https://github.com/maniacbug/RF24"> ManiacBug on GitHub (Original Library Author)</a>
 */

#endif // __RF24_H__