nRF24L01P_Maniacbug.h

00001 /*
00002     Copyright (c) 2007 Stefan Engelke <mbox@stefanengelke.de>
00003 
00004     Permission is hereby granted, free of charge, to any person 
00005     obtaining a copy of this software and associated documentation 
00006     files (the "Software"), to deal in the Software without 
00007     restriction, including without limitation the rights to use, copy, 
00008     modify, merge, publish, distribute, sublicense, and/or sell copies 
00009     of the Software, and to permit persons to whom the Software is 
00010     furnished to do so, subject to the following conditions:
00011 
00012     The above copyright notice and this permission notice shall be 
00013     included in all copies or substantial portions of the Software.
00014 
00015     THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 
00016     EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF 
00017     MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 
00018     NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT 
00019     HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, 
00020     WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 
00021     OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER 
00022     DEALINGS IN THE SOFTWARE.
00023 */
00024 
00025 /* Memory Map */
00026 #define CONFIG      0x00
00027 #define EN_AA       0x01
00028 #define EN_RXADDR   0x02
00029 #define SETUP_AW    0x03
00030 #define SETUP_RETR  0x04
00031 #define RF_CH       0x05
00032 #define RF_SETUP    0x06
00033 #define RF_STATUS   0x07
00034 #define OBSERVE_TX  0x08
00035 #define CD          0x09
00036 #define RX_ADDR_P0  0x0A
00037 #define RX_ADDR_P1  0x0B
00038 #define RX_ADDR_P2  0x0C
00039 #define RX_ADDR_P3  0x0D
00040 #define RX_ADDR_P4  0x0E
00041 #define RX_ADDR_P5  0x0F
00042 #define TX_ADDR     0x10
00043 #define RX_PW_P0    0x11
00044 #define RX_PW_P1    0x12
00045 #define RX_PW_P2    0x13
00046 #define RX_PW_P3    0x14
00047 #define RX_PW_P4    0x15
00048 #define RX_PW_P5    0x16
00049 #define FIFO_STATUS 0x17
00050 #define DYNPD       0x1C
00051 #define FEATURE     0x1D
00052 
00053 /* Bit Mnemonics */
00054 #define MASK_RX_DR  6
00055 #define MASK_TX_DS  5
00056 #define MASK_MAX_RT 4
00057 #define EN_CRC      3
00058 #define CRCO        2
00059 #define PWR_UP      1
00060 #define PRIM_RX     0
00061 #define ENAA_P5     5
00062 #define ENAA_P4     4
00063 #define ENAA_P3     3
00064 #define ENAA_P2     2
00065 #define ENAA_P1     1
00066 #define ENAA_P0     0
00067 #define ERX_P5      5
00068 #define ERX_P4      4
00069 #define ERX_P3      3
00070 #define ERX_P2      2
00071 #define ERX_P1      1
00072 #define ERX_P0      0
00073 #define AW          0
00074 #define ARD         4
00075 #define ARC         0
00076 #define PLL_LOCK    4
00077 #define RF_DR       3
00078 #define RF_PWR      6
00079 #define RX_DR       6
00080 #define TX_DS       5
00081 #define MAX_RT      4
00082 #define RX_P_NO     1
00083 #define TX_FULL     0
00084 #define PLOS_CNT    4
00085 #define ARC_CNT     0
00086 #define TX_REUSE    6
00087 #define FIFO_FULL   5
00088 #define TX_EMPTY    4
00089 #define RX_FULL     1
00090 #define RX_EMPTY    0
00091 #define DPL_P5      5
00092 #define DPL_P4      4
00093 #define DPL_P3      3
00094 #define DPL_P2      2
00095 #define DPL_P1      1
00096 #define DPL_P0      0
00097 #define EN_DPL      2
00098 #define EN_ACK_PAY  1
00099 #define EN_DYN_ACK  0
00100 
00101 /* Instruction Mnemonics */
00102 #define R_REGISTER    0x00
00103 #define W_REGISTER    0x20
00104 #define REGISTER_MASK 0x1F
00105 #define ACTIVATE      0x50
00106 #define R_RX_PL_WID   0x60
00107 #define R_RX_PAYLOAD  0x61
00108 #define W_TX_PAYLOAD  0xA0
00109 #define W_ACK_PAYLOAD 0xA8
00110 #define FLUSH_TX      0xE1
00111 #define FLUSH_RX      0xE2
00112 #define REUSE_TX_PL   0xE3
00113 #define RF_NOP           0xFF
00114 
00115 /* Non-P omissions */
00116 #define LNA_HCURR   0
00117 
00118 /* P model memory Map */
00119 #define RPD         0x09
00120 
00121 /* P model bit Mnemonics */
00122 #define RF_DR_LOW   5
00123 #define RF_DR_HIGH  3
00124 #define RF_PWR_LOW  1
00125 #define RF_PWR_HIGH 2
00126 
00127 #define RF_HIGH        1
00128 #define RF_LOW         0
00129 #define _BV(n) (1 << n)
00130 
00131 /*
00132  Copyright (C) 2011 J. Coliz <maniacbug@ymail.com>
00133 
00134  This program is free software; you can redistribute it and/or
00135  modify it under the terms of the GNU General Public License
00136  version 2 as published by the Free Software Foundation.
00137  */
00138 
00139 /**
00140  * @file RF24.h
00141  *
00142  * Class declaration for RF24 and helper enums
00143  */
00144 
00145 #ifndef __RF24_H__
00146 #define __RF24_H__
00147 
00148 #include <mbed.h>
00149 
00150 /**
00151  * Power Amplifier level.
00152  *
00153  * For use with setPALevel()
00154  */
00155 typedef enum { RF24_PA_MIN = 0,RF24_PA_LOW, RF24_PA_HIGH, RF24_PA_MAX, RF24_PA_ERROR } rf24_pa_dbm_e ;
00156 
00157 /**
00158  * Data rate.  How fast data moves through the air.
00159  *
00160  * For use with setDataRate()
00161  */
00162 typedef enum { RF24_1MBPS = 0, RF24_2MBPS, RF24_250KBPS } rf24_datarate_e;
00163 
00164 /**
00165  * CRC Length.  How big (if any) of a CRC is included.
00166  *
00167  * For use with setCRCLength()
00168  */
00169 typedef enum { RF24_CRC_DISABLED = 0, RF24_CRC_8, RF24_CRC_16 } rf24_crclength_e;
00170 
00171 /**
00172  * Driver for nRF24L01(+) 2.4GHz Wireless Transceiver
00173  */
00174 
00175 class RF24
00176 {
00177 private:
00178   DigitalOut ce_pin; /**< "Chip Enable" pin, activates the RX or TX role */
00179   DigitalOut csn_pin; /**< SPI Chip select */
00180   bool wide_band; /* 2Mbs data rate in use? */
00181   bool p_variant; /* False for RF24L01 and true for RF24L01P */
00182   uint8_t payload_size; /**< Fixed size of payloads */
00183   bool ack_payload_available; /**< Whether there is an ack payload waiting */
00184   bool dynamic_payloads_enabled; /**< Whether dynamic payloads are enabled. */ 
00185   uint8_t ack_payload_length; /**< Dynamic size of pending ack payload. */
00186   uint64_t pipe0_reading_address; /**< Last address set on pipe 0 for reading. */
00187   SPI spi;
00188   Timer mainTimer;
00189 
00190 protected:
00191   /**
00192    * @name Low-level internal interface.
00193    *
00194    *  Protected methods that address the chip directly.  Regular users cannot
00195    *  ever call these.  They are documented for completeness and for developers who
00196    *  may want to extend this class.
00197    */
00198   /**@{*/
00199 
00200   /**
00201    * Set chip select pin
00202    *
00203    * Running SPI bus at PI_CLOCK_DIV2 so we don't waste time transferring data
00204    * and best of all, we make use of the radio's FIFO buffers. A lower speed
00205    * means we're less likely to effectively leverage our FIFOs and pay a higher
00206    * AVR runtime cost as toll.
00207    *
00208    * @param mode HIGH to take this unit off the SPI bus, LOW to put it on
00209    */
00210   void csn(int mode);
00211 
00212   /**
00213    * Set chip enable
00214    *
00215    * @param level HIGH to actively begin transmission or LOW to put in standby.  Please see data sheet
00216    * for a much more detailed description of this pin.
00217    */
00218   void ce(int level);  
00219 
00220 
00221   /**
00222    * Read a chunk of data in from a register
00223    *
00224    * @param reg Which register. Use constants from nRF24L01.h
00225    * @param buf Where to put the data
00226    * @param len How many bytes of data to transfer
00227    * @return Current value of status register
00228    */
00229   uint8_t read_register(uint8_t reg, uint8_t* buf, uint8_t len);
00230 
00231   /**
00232    * Read single byte from a register
00233    *
00234    * @param reg Which register. Use constants from nRF24L01.h
00235    * @return Current value of register @p reg
00236    */
00237   uint8_t read_register(uint8_t reg);
00238 
00239   /**
00240    * Write a chunk of data to a register
00241    *
00242    * @param reg Which register. Use constants from nRF24L01.h
00243    * @param buf Where to get the data
00244    * @param len How many bytes of data to transfer
00245    * @return Current value of status register
00246    */
00247   uint8_t write_register(uint8_t reg, const uint8_t* buf, uint8_t len);
00248 
00249   /**
00250    * Write a single byte to a register
00251    *
00252    * @param reg Which register. Use constants from nRF24L01.h
00253    * @param value The new value to write
00254    * @return Current value of status register
00255    */
00256   uint8_t write_register(uint8_t reg, uint8_t value);
00257 
00258   /**
00259    * Write the transmit payload
00260    *
00261    * The size of data written is the fixed payload size, see getPayloadSize()
00262    *
00263    * @param buf Where to get the data
00264    * @param len Number of bytes to be sent
00265    * @return Current value of status register
00266    */
00267   uint8_t write_payload(const void* buf, uint8_t len);
00268 
00269   /**
00270    * Read the receive payload
00271    *
00272    * The size of data read is the fixed payload size, see getPayloadSize()
00273    *
00274    * @param buf Where to put the data
00275    * @param len Maximum number of bytes to read
00276    * @return Current value of status register
00277    */
00278   uint8_t read_payload(void* buf, uint8_t len);
00279 
00280 
00281   /**
00282    * Decode and print the given status to stdout
00283    *
00284    * @param status Status value to print
00285    *
00286    * @warning Does nothing if stdout is not defined.  See fdevopen in stdio.h
00287    */
00288   void print_status(uint8_t status);
00289 
00290   /**
00291    * Decode and print the given 'observe_tx' value to stdout
00292    *
00293    * @param value The observe_tx value to print
00294    *
00295    * @warning Does nothing if stdout is not defined.  See fdevopen in stdio.h
00296    */
00297   void print_observe_tx(uint8_t value);
00298 
00299   /**
00300    * Print the name and value of an 8-bit register to stdout
00301    *
00302    * Optionally it can print some quantity of successive
00303    * registers on the same line.  This is useful for printing a group
00304    * of related registers on one line.
00305    *
00306    * @param name Name of the register
00307    * @param reg Which register. Use constants from nRF24L01.h
00308    * @param qty How many successive registers to print
00309    */
00310   void print_byte_register(const char* name, uint8_t reg, uint8_t qty = 1);
00311 
00312   /**
00313    * Print the name and value of a 40-bit address register to stdout
00314    *
00315    * Optionally it can print some quantity of successive
00316    * registers on the same line.  This is useful for printing a group
00317    * of related registers on one line.
00318    *
00319    * @param name Name of the register
00320    * @param reg Which register. Use constants from nRF24L01.h
00321    * @param qty How many successive registers to print
00322    */
00323   void print_address_register(const char* name, uint8_t reg, uint8_t qty = 1);
00324 
00325   /**
00326    * Turn on or off the special features of the chip
00327    *
00328    * The chip has certain 'features' which are only available when the 'features'
00329    * are enabled.  See the datasheet for details.
00330    */
00331   void toggle_features(void);
00332   /**@}*/
00333 
00334 public:
00335   /**
00336    * @name Primary public interface
00337    *
00338    *  These are the main methods you need to operate the chip
00339    */
00340   /**@{*/
00341 
00342   /**
00343    * Constructor
00344    *
00345    * Creates a new instance of this driver.  Before using, you create an instance
00346    * and send in the unique pins that this chip is connected to.
00347    *
00348    * @param _cepin The pin attached to Chip Enable on the RF module
00349    * @param _cspin The pin attached to Chip Select
00350    */
00351   RF24(PinName mosi, PinName miso, PinName sck, PinName _csnpin, PinName _cepin);
00352 
00353   /**
00354    * Begin operation of the chip
00355    *
00356    * Call this in setup(), before calling any other methods.
00357    */
00358   void begin(void);
00359   
00360     /**
00361    * Retrieve the current status of the chip
00362    *
00363    * @return Current value of status register
00364    */
00365   uint8_t get_status(void);
00366     
00367   /**
00368    * Empty the receive buffer
00369    *
00370    * @return Current value of status register
00371    */
00372   uint8_t flush_rx(void);
00373 
00374   /**
00375    * Empty the transmit buffer
00376    *
00377    * @return Current value of status register
00378    */
00379   uint8_t flush_tx(void);
00380 
00381   /**
00382    * Start listening on the pipes opened for reading.
00383    *
00384    * Be sure to call openReadingPipe() first.  Do not call write() while
00385    * in this mode, without first calling stopListening().  Call
00386    * isAvailable() to check for incoming traffic, and read() to get it.
00387    */
00388   void startListening(void);
00389 
00390   /**
00391    * Stop listening for incoming messages
00392    *
00393    * Do this before calling write().
00394    */
00395   void stopListening(void);
00396 
00397   /**
00398    * Write to the open writing pipe
00399    *
00400    * Be sure to call openWritingPipe() first to set the destination
00401    * of where to write to.
00402    *
00403    * This blocks until the message is successfully acknowledged by
00404    * the receiver or the timeout/retransmit maxima are reached.  In
00405    * the current configuration, the max delay here is 60ms.
00406    *
00407    * The maximum size of data written is the fixed payload size, see
00408    * getPayloadSize().  However, you can write less, and the remainder
00409    * will just be filled with zeroes.
00410    *
00411    * @param buf Pointer to the data to be sent
00412    * @param len Number of bytes to be sent
00413    * @return True if the payload was delivered successfully false if not
00414    */
00415   bool write( const void* buf, uint8_t len );
00416 
00417   /**
00418    * Test whether there are bytes available to be read
00419    *
00420    * @return True if there is a payload available, false if none is
00421    */
00422   bool available(void);
00423 
00424   /**
00425    * Read the payload
00426    *
00427    * Return the last payload received
00428    *
00429    * The size of data read is the fixed payload size, see getPayloadSize()
00430    *
00431    * @note I specifically chose 'void*' as a data type to make it easier
00432    * for beginners to use.  No casting needed.
00433    *
00434    * @param buf Pointer to a buffer where the data should be written
00435    * @param len Maximum number of bytes to read into the buffer
00436    * @return True if the payload was delivered successfully false if not
00437    */
00438   bool read( void* buf, uint8_t len );
00439 
00440   /**
00441    * Open a pipe for writing
00442    *
00443    * Only one pipe can be open at once, but you can change the pipe
00444    * you'll listen to.  Do not call this while actively listening.
00445    * Remember to stopListening() first.
00446    *
00447    * Addresses are 40-bit hex values, e.g.:
00448    *
00449    * @code
00450    *   openWritingPipe(0xF0F0F0F0F0);
00451    * @endcode
00452    *
00453    * @param address The 40-bit address of the pipe to open.  This can be
00454    * any value whatsoever, as long as you are the only one writing to it
00455    * and only one other radio is listening to it.  Coordinate these pipe
00456    * addresses amongst nodes on the network.
00457    */
00458   void openWritingPipe(uint64_t address);
00459 
00460   /**
00461    * Open a pipe for reading
00462    *
00463    * Up to 6 pipes can be open for reading at once.  Open all the
00464    * reading pipes, and then call startListening().
00465    *
00466    * @see openWritingPipe
00467    *
00468    * @warning Pipes 1-5 should share the first 32 bits.
00469    * Only the least significant byte should be unique, e.g.
00470    * @code
00471    *   openReadingPipe(1,0xF0F0F0F0AA);
00472    *   openReadingPipe(2,0xF0F0F0F066);
00473    * @endcode
00474    *
00475    * @warning Pipe 0 is also used by the writing pipe.  So if you open
00476    * pipe 0 for reading, and then startListening(), it will overwrite the
00477    * writing pipe.  Ergo, do an openWritingPipe() again before write().
00478    *
00479    * @todo Enforce the restriction that pipes 1-5 must share the top 32 bits
00480    *
00481    * @param number Which pipe# to open, 0-5.
00482    * @param address The 40-bit address of the pipe to open.
00483    */
00484   void openReadingPipe(uint8_t number, uint64_t address);
00485 
00486   /**@}*/
00487   /**
00488    * @name Optional Configurators 
00489    *
00490    *  Methods you can use to get or set the configuration of the chip.
00491    *  None are required.  Calling begin() sets up a reasonable set of
00492    *  defaults.
00493    */
00494   /**@{*/
00495   /**
00496    * Set the number and delay of retries upon failed submit
00497    *
00498    * @param delay How long to wait between each retry, in multiples of 250us,
00499    * max is 15.  0 means 250us, 15 means 4000us.
00500    * @param count How many retries before giving up, max 15
00501    */
00502   void setRetries(uint8_t delay, uint8_t count);
00503 
00504   /**
00505    * Set RF communication channel
00506    *
00507    * @param channel Which RF channel to communicate on, 0-127
00508    */
00509   void setChannel(uint8_t channel);
00510 
00511   /**
00512    * Set Static Payload Size
00513    *
00514    * This implementation uses a pre-stablished fixed payload size for all
00515    * transmissions.  If this method is never called, the driver will always
00516    * transmit the maximum payload size (32 bytes), no matter how much
00517    * was sent to write().
00518    *
00519    * @todo Implement variable-sized payloads feature
00520    *
00521    * @param size The number of bytes in the payload
00522    */
00523   void setPayloadSize(uint8_t size);
00524 
00525   /**
00526    * Get Static Payload Size
00527    *
00528    * @see setPayloadSize()
00529    *
00530    * @return The number of bytes in the payload
00531    */
00532   uint8_t getPayloadSize(void);
00533 
00534   /**
00535    * Get Dynamic Payload Size
00536    *
00537    * For dynamic payloads, this pulls the size of the payload off
00538    * the chip
00539    *
00540    * @return Payload length of last-received dynamic payload
00541    */
00542   uint8_t getDynamicPayloadSize(void);
00543   
00544   /**
00545    * Enable custom payloads on the acknowledge packets
00546    *
00547    * Ack payloads are a handy way to return data back to senders without
00548    * manually changing the radio modes on both units.
00549    *
00550    * @see examples/pingpair_pl/pingpair_pl.pde
00551    */
00552   void enableAckPayload(void);
00553 
00554   /**
00555    * Enable dynamically-sized payloads
00556    *
00557    * This way you don't always have to send large packets just to send them
00558    * once in a while.  This enables dynamic payloads on ALL pipes.
00559    *
00560    * @see examples/pingpair_pl/pingpair_dyn.pde
00561    */
00562   void enableDynamicPayloads(void);
00563 
00564   /**
00565    * Determine whether the hardware is an nRF24L01+ or not.
00566    *
00567    * @return true if the hardware is nRF24L01+ (or compatible) and false
00568    * if its not.
00569    */
00570   bool isPVariant(void) ;
00571 
00572   /**
00573    * Enable or disable auto-acknowlede packets
00574    *
00575    * This is enabled by default, so it's only needed if you want to turn
00576    * it off for some reason.
00577    *
00578    * @param enable Whether to enable (true) or disable (false) auto-acks
00579    */
00580   void setAutoAck(bool enable);
00581 
00582   /**
00583    * Enable or disable auto-acknowlede packets on a per pipeline basis.
00584    *
00585    * AA is enabled by default, so it's only needed if you want to turn
00586    * it off/on for some reason on a per pipeline basis.
00587    *
00588    * @param pipe Which pipeline to modify
00589    * @param enable Whether to enable (true) or disable (false) auto-acks
00590    */
00591   void setAutoAck( uint8_t pipe, bool enable ) ;
00592 
00593   /**
00594    * Set Power Amplifier (PA) level to one of four levels.
00595    * Relative mnemonics have been used to allow for future PA level
00596    * changes. According to 6.5 of the nRF24L01+ specification sheet,
00597    * they translate to: RF24_PA_MIN=-18dBm, RF24_PA_LOW=-12dBm,
00598    * RF24_PA_MED=-6dBM, and RF24_PA_HIGH=0dBm.
00599    *
00600    * @param level Desired PA level.
00601    */
00602   void setPALevel( rf24_pa_dbm_e level ) ;
00603 
00604   /**
00605    * Fetches the current PA level.
00606    *
00607    * @return Returns a value from the rf24_pa_dbm_e enum describing
00608    * the current PA setting. Please remember, all values represented
00609    * by the enum mnemonics are negative dBm. See setPALevel for
00610    * return value descriptions.
00611    */
00612   rf24_pa_dbm_e getPALevel( void ) ;
00613 
00614   /**
00615    * Set the transmission data rate
00616    *
00617    * @warning setting RF24_250KBPS will fail for non-plus units
00618    *
00619    * @param speed RF24_250KBPS for 250kbs, RF24_1MBPS for 1Mbps, or RF24_2MBPS for 2Mbps
00620    * @return true if the change was successful
00621    */
00622   bool setDataRate(rf24_datarate_e speed);
00623   
00624   /**
00625    * Fetches the transmission data rate
00626    *
00627    * @return Returns the hardware's currently configured datarate. The value
00628    * is one of 250kbs, RF24_1MBPS for 1Mbps, or RF24_2MBPS, as defined in the
00629    * rf24_datarate_e enum.
00630    */
00631   rf24_datarate_e getDataRate( void ) ;
00632 
00633   /**
00634    * Set the CRC length
00635    *
00636    * @param length RF24_CRC_8 for 8-bit or RF24_CRC_16 for 16-bit
00637    */
00638   void setCRCLength(rf24_crclength_e length);
00639 
00640   /**
00641    * Get the CRC length
00642    *
00643    * @return RF24_DISABLED if disabled or RF24_CRC_8 for 8-bit or RF24_CRC_16 for 16-bit
00644    */
00645   rf24_crclength_e getCRCLength(void);
00646 
00647   /**
00648    * Disable CRC validation
00649    *
00650    */
00651   void disableCRC( void ) ;
00652 
00653   /**@}*/
00654   /**
00655    * @name Advanced Operation 
00656    *
00657    *  Methods you can use to drive the chip in more advanced ways 
00658    */
00659   /**@{*/
00660 
00661   /**
00662    * Print a giant block of debugging information to stdout
00663    *
00664    * @warning Does nothing if stdout is not defined.  See fdevopen in stdio.h
00665    */
00666   void printDetails(void);
00667 
00668   /**
00669    * Enter low-power mode
00670    *
00671    * To return to normal power mode, either write() some data or
00672    * startListening, or powerUp().
00673    */
00674   void powerDown(void);
00675 
00676   /**
00677    * Leave low-power mode - making radio more responsive
00678    *
00679    * To return to low power mode, call powerDown().
00680    */
00681   void powerUp(void) ;
00682 
00683   /**
00684    * Test whether there are bytes available to be read
00685    *
00686    * Use this version to discover on which pipe the message
00687    * arrived.
00688    *
00689    * @param[out] pipe_num Which pipe has the payload available
00690    * @return True if there is a payload available, false if none is
00691    */
00692   bool available(uint8_t* pipe_num);
00693 
00694   /**
00695    * Non-blocking write to the open writing pipe
00696    *
00697    * Just like write(), but it returns immediately. To find out what happened
00698    * to the send, catch the IRQ and then call whatHappened().
00699    *
00700    * @see write()
00701    * @see whatHappened()
00702    *
00703    * @param buf Pointer to the data to be sent
00704    * @param len Number of bytes to be sent
00705    * @return True if the payload was delivered successfully false if not
00706    */
00707   void startWrite( const void* buf, uint8_t len );
00708 
00709   /**
00710    * Write an ack payload for the specified pipe
00711    *
00712    * The next time a message is received on @p pipe, the data in @p buf will
00713    * be sent back in the acknowledgement.
00714    *
00715    * @warning According to the data sheet, only three of these can be pending
00716    * at any time.  I have not tested this.
00717    *
00718    * @param pipe Which pipe# (typically 1-5) will get this response.
00719    * @param buf Pointer to data that is sent
00720    * @param len Length of the data to send, up to 32 bytes max.  Not affected
00721    * by the static payload set by setPayloadSize().
00722    */
00723   void writeAckPayload(uint8_t pipe, const void* buf, uint8_t len);
00724 
00725   /**
00726    * Determine if an ack payload was received in the most recent call to
00727    * write().
00728    *
00729    * Call read() to retrieve the ack payload.
00730    *
00731    * @warning Calling this function clears the internal flag which indicates
00732    * a payload is available.  If it returns true, you must read the packet
00733    * out as the very next interaction with the radio, or the results are
00734    * undefined.
00735    *
00736    * @return True if an ack payload is available.
00737    */
00738   bool isAckPayloadAvailable(void);
00739 
00740   /**
00741    * Call this when you get an interrupt to find out why
00742    *
00743    * Tells you what caused the interrupt, and clears the state of
00744    * interrupts.
00745    *
00746    * @param[out] tx_ok The send was successful (TX_DS)
00747    * @param[out] tx_fail The send failed, too many retries (MAX_RT)
00748    * @param[out] rx_ready There is a message waiting to be read (RX_DS)
00749    */
00750   void whatHappened(bool& tx_ok,bool& tx_fail,bool& rx_ready);
00751 
00752   /**
00753    * Test whether there was a carrier on the line for the
00754    * previous listening period.
00755    *
00756    * Useful to check for interference on the current channel.
00757    *
00758    * @return true if was carrier, false if not
00759    */
00760   bool testCarrier(void);
00761 
00762   /**
00763    * Test whether a signal (carrier or otherwise) greater than
00764    * or equal to -64dBm is present on the channel. Valid only
00765    * on nRF24L01P (+) hardware. On nRF24L01, use testCarrier().
00766    *
00767    * Useful to check for interference on the current channel and
00768    * channel hopping strategies.
00769    *
00770    * @return true if signal => -64dBm, false if not
00771    */
00772   bool testRPD(void) ;
00773   
00774   uint8_t min(uint8_t, uint8_t);
00775 };
00776 
00777 
00778 #endif // __RF24_H__
00779 // vim:ai:cin:sts=2 sw=2 ft=cpp