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 wide_band; /* 2Mbs data rate in use? */
  bool p_variant; /* False for RF24L01 and true for RF24L01P */
  uint8_t payload_size; /**< Fixed size of payloads */
  bool ack_payload_available; /**< Whether there is an ack payload waiting */
  bool dynamic_payloads_enabled; /**< Whether dynamic payloads are enabled. */ 
  uint8_t ack_payload_length; /**< Dynamic size of pending ack payload. */
  uint64_t pipe0_reading_address; /**< Last address set on pipe 0 for reading. */

protected:
  /**
   * @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(int 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(int 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);

  /**
   * 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);

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

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.
   */
  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().
   */
  void stopListening(void);

  /**
   * 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.
   *
   * @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 );

  /**
   * Test whether there are bytes available to be read
   *
   * @return True if there is a payload available, false if none is
   */
  bool available(void);

  /**
   * Read the payload
   *
   * Return the last payload received
   *
   * 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.
   *
   * @param buf Pointer to a buffer where the data should be written
   * @param len Maximum number of bytes to read into the buffer
   * @return True if the payload was delivered successfully false if not
   */
  bool read( void* buf, uint8_t len );

  /**
   * Open a pipe for writing
   *
   * Only one pipe can be open at once, but you can change the pipe
   * you'll listen to.  Do not call this while actively listening.
   * Remember to stopListening() first.
   *
   * Addresses are 40-bit hex values, e.g.:
   *
   * @code
   *   openWritingPipe(0xF0F0F0F0F0);
   * @endcode
   *
   * @param address The 40-bit address of the pipe to open.  This can be
   * any value whatsoever, as long as you are the only one writing to it
   * and only one other radio is listening to it.  Coordinate these pipe
   * addresses amongst nodes on the network.
   */
  void openWritingPipe(uint64_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
   *
   * @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().
   *
   * @todo Enforce the restriction that pipes 1-5 must share the top 32 bits
   *
   * @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);

  /**@}*/
  /**
   * @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
   *
   * @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.
   * Relative mnemonics have been used to allow for future PA level
   * changes. According to 6.5 of the nRF24L01+ specification sheet,
   * they translate to: RF24_PA_MIN=-18dBm, RF24_PA_LOW=-12dBm,
   * RF24_PA_MED=-6dBM, and RF24_PA_HIGH=0dBm.
   *
   * @param level Desired PA level.
   */
  void setPALevel( rf24_pa_dbm_e level ) ;

  /**
   * Fetches the current PA level.
   *
   * @return Returns a value from the rf24_pa_dbm_e enum describing
   * the current PA setting. Please remember, all values represented
   * by the enum mnemonics are negative dBm. See setPALevel for
   * return value descriptions.
   */
  rf24_pa_dbm_e 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 ) ;

  /**@}*/
  /**
   * @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);

  /**
   * Enter low-power mode
   *
   * To return to normal power mode, either write() some data or
   * startListening, or powerUp().
   */
  void powerDown(void);

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

  /**
   * Test whether there are bytes available to be read
   *
   * Use this version to discover on which pipe the message
   * arrived.
   *
   * @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);

  /**
   * 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().
   *
   * @see write()
   * @see whatHappened()
   *
   * @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
   */
  void startWrite( const void* buf, uint8_t len );

  /**
   * 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.  I have not tested this.
   *
   * @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);

  /**
   * Determine if an ack payload was received in the most recent call to
   * write().
   *
   * Call read() to retrieve the ack payload.
   *
   * @warning Calling this function clears the internal flag which indicates
   * a payload is available.  If it returns true, you must read the packet
   * out as the very next interaction with the radio, or the results are
   * undefined.
   *
   * @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);

  /**
   * 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; } 

  /**@}*/
};

/**
 * @example GettingStarted.pde
 *
 * This is an example which corresponds to my "Getting Started" blog post:
 * <a style="text-align:center" href="http://maniacbug.wordpress.com/2011/11/02/getting-started-rf24/">Getting Started with nRF24L01+ on Arduino</a>. 
 *
 * 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 
 * with the serial monitor and 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.
 */

/**
 * @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 pingpair.pde
 *
 * This is an example of how to use the RF24 class.  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 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 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_pl.pde
 *
 * This is an example of how to do two-way communication without changing
 * transmit/receive modes.  Here, a payload is set to the transmitter within
 * the Ack packet of each transmission.  Note that the payload is set BEFORE
 * the sender's message arrives.
 */

/**
 * @example pingpair_irq.pde
 *
 * This is an example of how to user interrupts to interact with the radio.
 * It builds on the pingpair_pl example, and uses ack payloads.
 */

/**
 * @example pingpair_sleepy.pde
 *
 * This is an example of how to use the RF24 class to create a battery-
 * efficient system.  It is just like the pingpair.pde example, but the
 * ping node powers down the radio and sleeps the MCU after every
 * ping/pong cycle.
 */

/**
 * @example scanner.pde
 *
 * 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 Driver for nRF24L01(+) 2.4GHz Wireless Transceiver
 *
 * @section Goals Design Goals
 * 
 * This library is designed to be...
 * @li Maximally compliant with the intended operation of the chip
 * @li Easy for beginners to use
 * @li Consumed with a public interface that's similiar to other Arduino standard libraries
 *
 * @section News News
 * 
 * NOW COMPATIBLE WITH ARDUINO 1.0 - The 'master' branch and all examples work with both Arduino 1.0 and earlier versions.  
 * Please <a href="https://github.com/maniacbug/RF24/issues/new">open an issue</a> if you find any problems using it with any version of Arduino.
 *
 * NOW COMPATIBLE WITH MAPLE - RF24 has been tested with the 
 * <a href="http://leaflabs.com/store/#Maple-Native">Maple Native</a>, 
 * and should work with any Maple board.  See the pingpair_maple example.
 * Note that only the pingpair_maple example has been tested on Maple, although
 * the others can certainly be adapted.
 *
 * @section Useful Useful References
 * 
 * Please refer to:
 *
 * @li <a href="http://maniacbug.github.com/RF24/">Documentation Main Page</a>
 * @li <a href="http://maniacbug.github.com/RF24/classRF24.html">RF24 Class Documentation</a>
 * @li <a href="https://github.com/maniacbug/RF24/">Source Code</a>
 * @li <a href="https://github.com/maniacbug/RF24/archives/master">Downloads Page</a>
 * @li <a href="http://www.nordicsemi.com/files/Product/data_sheet/nRF24L01_Product_Specification_v2_0.pdf">Chip Datasheet</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 More More Information
 *
 * @subpage FAQ
 *
 * @section Projects Projects
 *
 * Stuff I have built with RF24
 *
 * <img src="http://farm7.staticflickr.com/6044/6307669179_a8d19298a6_m.jpg" width="240" height="160" alt="RF24 Getting Started - Finished Product">
 *
 * <a style="text-align:center" href="http://maniacbug.wordpress.com/2011/11/02/getting-started-rf24/">Getting Started with nRF24L01+ on Arduino</a> 
 *
 * <img src="http://farm8.staticflickr.com/7159/6645514331_38eb2bdeaa_m.jpg" width="240" height="160" alt="Nordic FOB and nRF24L01+">
 *
 * <a style="text-align:center" href="http://maniacbug.wordpress.com/2012/01/08/nordic-fob/">Using the Sparkfun Nordic FOB</a> 
 *
 * <img src="http://farm7.staticflickr.com/6097/6224308836_b9b3b421a3_m.jpg" width="240" height="160" alt="RF Duinode V3 (2V4)">
 *
 * <a href="http://maniacbug.wordpress.com/2011/10/19/sensor-node/">Low-Power Wireless Sensor Node</a>
 *
 * <img src="http://farm8.staticflickr.com/7012/6489477865_b56edb629b_m.jpg" width="240" height="161" alt="nRF24L01+ connected to Leaf Labs Maple Native">
 *
 * <a href="http://maniacbug.wordpress.com/2011/12/14/nrf24l01-running-on-maple-3/">nRF24L01+ Running on Maple</a>
 */

#endif // __RF24_H__
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