RF24 class¶

class RF24¶

RF24::RF24(rf24_gpio_pin_t _cepin, rf24_gpio_pin_t _cspin, uint32_t _spi_speed = RF24_SPI_SPEED)¶

RF24 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.

See Related Pages for device specific information

Parameters:

rf24_gpio_pin_t _cepin¶

The pin attached to Chip Enable on the RF module

rf24_gpio_pin_t _cspin¶

The pin attached to Chip Select (often labeled CSN) on the radio module.

• For the Arduino Due board, the Arduino Due extended SPI feature is not supported. This means that the Due’s pins 4, 10, or 52 are not mandated options (can use any digital output pin) for the radio’s CSN pin.

uint32_t _spi_speed = RF24_SPI_SPEED¶

The SPI speed in Hz ie: 1000000 == 1Mhz

• Users can specify default SPI speed by modifying RF24_SPI_SPEED in RF24_config.h

  • For Arduino, the default SPI speed will only be properly configured this way on devices supporting SPI TRANSACTIONS

  • Older/Unsupported Arduino devices will use a default clock divider & settings configuration

  • For Linux: The old way of setting SPI speeds using BCM2835 driver enums has been removed as of v1.3.7

bool RF24::begin(void)¶

Begin operation of the chip

Call this in setup(), before calling any other methods.

if (!radio.begin()) {
  Serial.println(F("radio hardware not responding!"));
  while (1) {} // hold program in infinite loop to prevent subsequent errors
}

Returns:

• true if the radio was successfully initialized

• false if the MCU failed to communicate with the radio hardware

bool RF24::begin(_SPI *spiBus)¶

Same as begin(), but allows specifying a non-default SPI bus to use.

See also

Review the Arduino support page.

Note

This function assumes the SPI::begin() method was called before to calling this function.

Warning

This function is for the Arduino platforms only

Parameters:

_SPI *spiBus¶

A pointer or reference to an instantiated SPI bus object. The _SPI datatype is a “wrapped” definition that will represent various SPI implementations based on the specified platform.

Returns:

same result as begin()

Dynamically Instantiated Pins¶

RF24::RF24(uint32_t _spi_speed = RF24_SPI_SPEED)¶

A constructor for initializing the radio’s hardware dynamically

Warning

You MUST use begin(rf24_gpio_pin_t, rf24_gpio_pin_t) or begin(_SPI*, rf24_gpio_pin_t, rf24_gpio_pin_t) to pass both the digital output pin numbers connected to the radio’s CE and CSN pins.

Parameters:

uint32_t _spi_speed = RF24_SPI_SPEED¶

The SPI speed in Hz ie: 1000000 == 1Mhz

• Users can specify default SPI speed by modifying RF24_SPI_SPEED in RF24_config.h

  • For Arduino, the default SPI speed will only be properly configured this way on devices supporting SPI TRANSACTIONS

  • Older/Unsupported Arduino devices will use a default clock divider & settings configuration

  • For Linux: The old way of setting SPI speeds using BCM2835 driver enums has been removed as of v1.3.7

bool RF24::begin(rf24_gpio_pin_t _cepin, rf24_gpio_pin_t _cspin)¶

Same as begin(), but allows dynamically specifying a CE pin and CSN pin to use.

Parameters:

rf24_gpio_pin_t _cepin¶

The pin attached to Chip Enable on the RF module

rf24_gpio_pin_t _cspin¶

The pin attached to Chip Select (often labeled CSN) on the radio module.

• For the Arduino Due board, the Arduino Due extended SPI feature is not supported. This means that the Due’s pins 4, 10, or 52 are not mandated options (can use any digital output pin) for the radio’s CSN pin.

Returns:

same result as begin()

bool RF24::begin(_SPI *spiBus, rf24_gpio_pin_t _cepin, rf24_gpio_pin_t _cspin)¶

Same as begin(), but allows dynamically specifying a SPI bus, CE pin, and CSN pin to use.

See also

Review the Arduino support page.

Note

This function assumes the SPI::begin() method was called before to calling this function.

Warning

This function is for the Arduino platforms only

Parameters:

_SPI *spiBus¶

A pointer or reference to an instantiated SPI bus object. The _SPI datatype is a “wrapped” definition that will represent various SPI implementations based on the specified platform.

rf24_gpio_pin_t _cepin¶

The pin attached to Chip Enable on the RF module

rf24_gpio_pin_t _cspin¶

The pin attached to Chip Select (often labeled CSN) on the radio module.

• For the Arduino Due board, the Arduino Due extended SPI feature is not supported. This means that the Due’s pins 4, 10, or 52 are not mandated options (can use any digital output pin) for the radio’s CSN pin.

Returns:

same result as begin()

Basic API¶

void RF24::startListening(void)¶

Start listening on the pipes opened for reading.

1. Be sure to call openReadingPipe() first.

2. Do not call write() while in this mode, without first calling stopListening().

3. Call available() to check for incoming traffic, and read() to get it.

Open reading pipe 1 using address 0xCCCECCCECC

byte address[] = {0xCC, 0xCE, 0xCC, 0xCE, 0xCC};
radio.openReadingPipe(1,address);
radio.startListening();

Note

If there was a call to openReadingPipe() about pipe 0 prior to calling this function, then this function will re-write the address that was last set to reading pipe 0. This is because openWritingPipe() will overwrite the address to reading pipe 0 for proper auto-ack functionality.

void RF24::stopListening(void)¶

Stop listening for incoming messages, and switch to transmit mode.

Do this before calling write().

radio.stopListening();
radio.write(&data, sizeof(data));

Note

When the ACK payloads feature is enabled, the TX FIFO buffers are flushed when calling this function. This is meant to discard any ACK payloads that were not appended to acknowledgment packets.

bool RF24::available(void)¶

Check whether there are bytes available to be read

if(radio.available()){
  radio.read(&data,sizeof(data));
}

See also

available(uint8_t*)

Warning

This function relies on the information about the pipe number that received the next available payload. According to the datasheet, the data about the pipe number that received the next available payload is “unreliable” during a FALLING transition on the IRQ pin. This means you should call whatHappened() before calling this function during an ISR (Interrupt Service Routine). For example:

void isrCallbackFunction() {
  bool tx_ds, tx_df, rx_dr;
  radio.whatHappened(tx_ds, tx_df, rx_dr); // resets the IRQ pin to HIGH
  radio.available();                       // returned data should now be reliable
}

void setup() {
  pinMode(IRQ_PIN, INPUT);
  attachInterrupt(digitalPinToInterrupt(IRQ_PIN), isrCallbackFunction, FALLING);
}

Returns:

True if there is a payload available, false if none is

bool RF24::available(uint8_t *pipe_num)¶

Test whether there are bytes available to be read from the FIFO buffers.

Note

This function is named available_pipe() in the python wrapper.

Additionally, the available_pipe() function (which takes no arguments) returns a 2 item tuple containing (ordered by tuple’s indices):

• A boolean describing if there is a payload available to read from the RX FIFO buffers.

• The pipe number that received the next available payload in the RX FIFO buffers. If the item at the tuple’s index 0 is False, then this pipe number is invalid.

To use this function in python:

# let `radio` be the instantiated RF24 object
has_payload, pipe_number = radio.available_pipe()  # expand the tuple to 2 variables
if has_payload:
    print("Received a payload with pipe", pipe_number)

Warning

According to the datasheet, the data saved to pipe_num is “unreliable” during a FALLING transition on the IRQ pin. This means you should call whatHappened() before calling this function during an ISR (Interrupt Service Routine). For example:

void isrCallbackFunction() {
  bool tx_ds, tx_df, rx_dr;
  radio.whatHappened(tx_ds, tx_df, rx_dr); // resets the IRQ pin to HIGH
  uint8_t pipe;                            // initialize pipe data
  radio.available(&pipe);                  // pipe data should now be reliable
}

void setup() {
  pinMode(IRQ_PIN, INPUT);
  attachInterrupt(digitalPinToInterrupt(IRQ_PIN), isrCallbackFunction, FALLING);
}

Parameters:

uint8_t *pipe_num¶

[out] Which pipe has the payload available

uint8_t pipeNum;
if(radio.available(&pipeNum)){
  radio.read(&data, sizeof(data));
  Serial.print("Received data on pipe ");
  Serial.println(pipeNum);
}

Returns:

• true if there is a payload available in the top (first out) level RX FIFO.

• false if there is nothing available in the RX FIFO because it is empty.

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

Read payload data from the RX FIFO buffer(s).

The length of data read is usually the next available payload’s length

See also

• getPayloadSize()

• getDynamicPayloadSize()

Remark

Remember that each call to read() fetches data from the RX FIFO beginning with the first byte from the first available payload. A payload is not removed from the RX FIFO until it’s entire length (or more) is fetched using read().

• If len parameter’s value is less than the available payload’s length, then the payload remains in the RX FIFO.

• If len parameter’s value is greater than the first of multiple available payloads, then the data saved to the buf parameter’s object will be supplemented with data from the next available payload.

• If len parameter’s value is greater than the last available payload’s length, then the last byte in the payload is used as padding for the data saved to the buf parameter’s object. The nRF24L01 will repeatedly use the last byte from the last payload even when read() is called with an empty RX FIFO.

Note

I specifically chose void* as a data type to make it easier for beginners to use. No casting needed.

Note

To use this function in the python wrapper, remember that only the len parameter is required because this function (in the python wrapper) returns the payload data as a buffer protocol object (bytearray object).

# let `radio` be the instantiated RF24 object
if radio.available():
    length = radio.getDynamicPayloadSize()  # or radio.getPayloadSize() for static payload sizes
    received_payload = radio.read(length)

Note

This function no longer returns a boolean. Use available to determine if packets are available. The RX_DR Interrupt flag is now cleared with this function instead of when calling available().

if(radio.available()) {
  radio.read(&data, sizeof(data));
}

Parameters:

void *buf¶

Pointer to a buffer where the data should be written

uint8_t len¶

Maximum number of bytes to read into the buffer. This value should match the length of the object referenced using the buf parameter. The absolute maximum number of bytes that can be read in one call is 32 (for dynamic payload lengths) or whatever number was previously passed to setPayloadSize() (for static payload lengths).

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

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 60-70ms.

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

radio.stopListening();
radio.write(&data,sizeof(data));

Note

The len parameter must be omitted when using the python wrapper because the length of the payload is determined automatically. To use this function in the python wrapper:

# let `radio` be the instantiated RF24 object
buffer = b"Hello World"  # a `bytes` object
radio.write(buffer)

Parameters:

const void *buf¶

Pointer to the data to be sent

uint8_t len¶

Number of bytes to be sent

Returns:

• true if the payload was delivered successfully and an acknowledgement (ACK packet) was received. If auto-ack is disabled, then any attempt to transmit will also return true (even if the payload was not received).

• false if the payload was sent but was not acknowledged with an ACK packet. This condition can only be reported if the auto-ack feature is on.

void RF24::openWritingPipe(const uint8_t *address)¶

New: Open a pipe for writing via byte array. Old addressing format retained for compatibility.

Only one writing pipe can be opened at once, but this function changes the address that is used to transmit (ACK payloads/packets do not apply here). Be sure to call stopListening() prior to calling this function.

Addresses are assigned via a byte array, default is 5 byte address length

uint8_t addresses[][6] = {"1Node", "2Node"};
radio.openWritingPipe(addresses[0]);

uint8_t address[] = { 0xCC, 0xCE, 0xCC, 0xCE, 0xCC };
radio.openWritingPipe(address);
address[0] = 0x33;
radio.openReadingPipe(1, address);

See also

• setAddressWidth()

• startListening()

Remark

There is no address length parameter because this function will always write the number of bytes that the radio addresses are configured to use (set with setAddressWidth()).

Warning

This function will overwrite the address set to reading pipe 0 as stipulated by the datasheet for proper auto-ack functionality in TX mode. Use this function to ensure proper transmission acknowledgement when the address set to reading pipe 0 (via openReadingPipe()) does not match the address passed to this function. If the auto-ack feature is disabled, then this function will still overwrite the address for reading pipe 0 regardless.

Parameters:

const uint8_t *address¶

The address to be used for outgoing transmissions (uses pipe 0). Coordinate this address amongst other receiving nodes (the pipe numbers don’t need to match).

void RF24::openWritingPipe(uint64_t address)¶

Open a pipe for writing

Deprecated:

For compatibility with old code only, see newer function openWritingPipe()

Addresses are 40-bit hex values, e.g.:

openWritingPipe(0xF0F0F0F0F0);

Parameters:

uint64_t address¶

The 40-bit address of the pipe to open.

void RF24::openReadingPipe(uint8_t number, const uint8_t *address)¶

Open a pipe for reading

Up to 6 pipes can be open for reading at once. Open all the required reading pipes, and then call startListening().

See also

• openWritingPipe()

• setAddressWidth()

There is no address length parameter because this function will always write the number of bytes (for pipes 0 and 1) that the radio addresses are configured to use (set with setAddressWidth()).

Note

Pipes 0 and 1 will store a full 5-byte address. Pipes 2-5 will technically only store a single byte, borrowing up to 4 additional bytes from pipe 1 per the assigned address width. Pipes 1-5 should share the same address, except the first byte. Only the first byte in the array should be unique, e.g.

uint8_t addresses[][6] = {"Prime", "2Node", "3xxxx", "4xxxx"};
openReadingPipe(0, addresses[0]); // address used is "Prime"
openReadingPipe(1, addresses[1]); // address used is "2Node"
openReadingPipe(2, addresses[2]); // address used is "3Node"
openReadingPipe(3, addresses[3]); // address used is "4Node"

Warning

If the reading pipe 0 is opened by this function, the address passed to this function (for pipe 0) will be restored at every call to startListening().

Read http://maniacalbits.blogspot.com/2013/04/rf24-addressing-nrf24l01-radios-require.html to understand how to avoid using malformed addresses. This address restoration is implemented because of the underlying necessary functionality of openWritingPipe().

Parameters:

uint8_t number¶

Which pipe to open. Only pipe numbers 0-5 are available, an address assigned to any pipe number not in that range will be ignored.

const uint8_t *address¶

The 24, 32 or 40 bit address of the pipe to open.

void RF24::openReadingPipe(uint8_t number, uint64_t address)¶

Open a pipe for reading

Deprecated:

For compatibility with old code only, see newer function openReadingPipe()

Note

Pipes 1-5 should share the first 32 bits. Only the least significant byte should be unique, e.g.

openReadingPipe(1, 0xF0F0F0F0AA);
openReadingPipe(2, 0xF0F0F0F066);

Warning

Pipe 0 is also used by the writing pipe so should typically be avoided as a reading pipe. If used, the reading pipe 0 address needs to be restored at every call to startListening().

See http://maniacalbits.blogspot.com/2013/04/rf24-addressing-nrf24l01-radios-require.html

Parameters:

uint8_t number¶

Which pipe# to open, 0-5.

uint64_t address¶

The 40-bit address of the pipe to open.

void RF24::closeReadingPipe(uint8_t pipe)¶

Close a pipe after it has been previously opened. Can be safely called without having previously opened a pipe.

Parameters:

uint8_t pipe¶

Which pipe number to close, any integer not in range [0, 5] is ignored.

Advanced API¶

bool RF24::isChipConnected()¶

Checks if the chip is connected to the SPI bus

bool RF24::isValid()¶

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.

Returns:

true if this is a legitimate radio

bool RF24::isPVariant(void)¶

Determine whether the hardware is an nRF24L01+ or not.

Returns:

true if the hardware is nRF24L01+ (or compatible) and false if its not.

void RF24::whatHappened(bool &tx_ok, bool &tx_fail, bool &rx_ready)¶

Call this when you get an Interrupt Request (IRQ) to find out why

This function describes what event triggered the IRQ pin to go active LOW and clears the status of all events.

See also

maskIRQ()

Note

This function expects no parameters in the python wrapper. Instead, this function returns a 3 item tuple describing the IRQ events’ status. To use this function in the python wrapper:

# let`radio` be the instantiated RF24 object
tx_ds, tx_df, rx_dr = radio.whatHappened()  # get IRQ status flags
print("tx_ds: {}, tx_df: {}, rx_dr: {}".format(tx_ds, tx_df, rx_dr))

Parameters:

bool &tx_ok¶

[out] The transmission attempt completed (TX_DS). This does not imply that the transmitted data was received by another radio, rather this only reports if the attempt to send was completed. This will always be true when the auto-ack feature is disabled.

bool &tx_fail¶

[out] The transmission failed to be acknowledged, meaning too many retries (MAX_RT) were made while expecting an ACK packet. This event is only triggered when auto-ack feature is enabled.

bool &rx_ready¶

[out] There is a newly received payload (RX_DR) saved to RX FIFO buffers. Remember that the RX FIFO can only hold up to 3 payloads. Once the RX FIFO is full, all further received transmissions are rejected until there is space to save new data in the RX FIFO buffers.

Debugging helpers¶

bool RF24::failureDetected¶

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.

The three main failure modes of the radio include:

1. Writing to radio: Radio unresponsive

   • Fixed internally by adding a timeout to the internal write functions in RF24 (failure handling)

2. Reading from radio: Available returns true always

   • Fixed by adding a timeout to available functions by the user. This is implemented internally in RF24Network.

3. Radio configuration settings are lost

   • Fixed by monitoring a value that is different from the default, and re-configuring the radio if this setting reverts to the default.

See the included example, GettingStarted_HandlingFailures

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
}

void RF24::printDetails(void)¶

Print a giant block of debugging information to stdout

Warning

Does nothing if stdout is not defined. See fdevopen in stdio.h The printf.h file is included with the library for Arduino.

#include <printf.h>
setup(){
  Serial.begin(115200);
  printf_begin();
  ...
}

void RF24::printPrettyDetails(void)¶

Print a giant block of debugging information to stdout. This function differs from printDetails() because it makes the information more understandable without having to look up the datasheet or convert hexadecimal to binary. Only use this function if your application can spare extra bytes of memory.

Note

If the automatic acknowledgements feature is configured differently for each pipe, then a binary representation is used in which bits 0-5 represent pipes 0-5 respectively. A 0 means the feature is disabled, and a 1 means the feature is enabled.

Warning

Does nothing if stdout is not defined. See fdevopen in stdio.h The printf.h file is included with the library for Arduino.

#include <printf.h>
setup(){
  Serial.begin(115200);
  printf_begin();
  // ...
}

uint8_t RF24::getARC(void)¶

Returns automatic retransmission count (ARC_CNT)

Value resets with each new transmission. Allows roughly estimating signal strength.

Returns:

Returns values from 0 to 15.

Advanced Transmission¶

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

Write for single NOACK writes. Optionally disable acknowledgements/auto-retries for a single payload using the multicast parameter set to true.

Can be used with enableAckPayload() to request a response

See also

• setAutoAck()

• write()

Note

The len parameter must be omitted when using the python wrapper because the length of the payload is determined automatically. To use this function in the python wrapper:

# let `radio` be the instantiated RF24 object
buffer = b"Hello World"  # a `bytes` object
radio.write(buffer, False)  # False = the multicast parameter

Parameters:

const void *buf¶

Pointer to the data to be sent

uint8_t len¶

Number of bytes to be sent

const bool multicast¶

Request ACK response (false), or no ACK response (true). Be sure to have called enableDynamicAck() at least once before setting this parameter.

Returns:

• true if the payload was delivered successfully and an acknowledgement (ACK packet) was received. If auto-ack is disabled, then any attempt to transmit will also return true (even if the payload was not received).

• false if the payload was sent but was not acknowledged with an ACK packet. This condition can only be reported if the auto-ack feature is on.

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

Write an acknowledgement (ACK) payload for the specified pipe

The next time a message is received on a specified pipe, the data in buf will be sent back in the ACK payload.

See also

• enableAckPayload()

• enableDynamicPayloads()

Note

ACK payloads are handled automatically by the radio chip when a regular payload is received. It is important to discard regular payloads in the TX FIFO (using flush_tx()) before loading the first ACK payload into the TX FIFO. This function can be called before and after calling startListening().

Note

ACK payloads are dynamic payloads. Calling enableAckPayload() will automatically enable dynamic payloads on pipe 0 (required for TX mode when expecting ACK payloads) & pipe 1. To use ACK payloads on any other pipe in RX mode, call enableDynamicPayloads().

Note

The len parameter must be omitted when using the python wrapper because the length of the payload is determined automatically. To use this function in the python wrapper:

# let `radio` be the instantiated RF24 object
buffer = b"Hello World"  # a `bytes` object
radio.writeAckPayload(1, buffer)  # load an ACK payload for response on pipe 1

Warning

Only three of these can be pending at any time as there are only 3 FIFO buffers. Dynamic payloads must be enabled.

Parameters:

uint8_t pipe¶

Which pipe# (typically 1-5) will get this response.

const void *buf¶

Pointer to data that is sent

uint8_t len¶

Length of the data to send, up to 32 bytes max. Not affected by the static payload size set by setPayloadSize().

Returns:

• true if the payload was loaded into the TX FIFO.

• false if the payload wasn’t loaded into the TX FIFO because it is already full or the ACK payload feature is not enabled using enableAckPayload().

bool RF24::writeFast(const void *buf, uint8_t len)¶

This will not block until the 3 FIFO buffers are filled with data. Once the FIFOs are full, writeFast() will simply wait for a buffer to become available or a transmission failure (returning true or false respectively).

See also

• setAutoAck()

• txStandBy()

• write()

• writeBlocking()

Warning

It is important to never keep the nRF24L01 in TX mode and FIFO full 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.

Use txStandBy() when this function returns false.

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.

Note

The len parameter must be omitted when using the python wrapper because the length of the payload is determined automatically. To use this function in the python wrapper:

# let `radio` be the instantiated RF24 object
buffer = b"Hello World"  # a `bytes` object
radio.writeFast(buffer)

Parameters:

const void *buf¶

Pointer to the data to be sent

uint8_t len¶

Number of bytes to be sent

Returns:

• true if the payload passed to buf was loaded in the TX FIFO.

• false if the payload passed to buf was not loaded in the TX FIFO because a previous payload already in the TX FIFO failed to transmit. This condition can only be reported if the auto-ack feature is on.

bool RF24::writeFast(const void *buf, uint8_t len, const bool multicast)¶

Similar to writeFast(const void*, uint8_t) but allows for single NOACK writes. Optionally disable acknowledgements/auto-retries for a single payload using the multicast parameter set to true.

See also

• setAutoAck()

• txStandBy()

• write()

• writeBlocking()

Note

The len parameter must be omitted when using the python wrapper because the length of the payload is determined automatically. To use this function in the python wrapper:

# let `radio` be the instantiated RF24 object
buffer = b"Hello World"  # a `bytes` object
radio.writeFast(buffer, False)  # False = the multicast parameter

Warning

If the auto-ack feature is enabled, then it is strongly encouraged to call txStandBy() when this function returns false.

Parameters:

const void *buf¶

Pointer to the data to be sent

uint8_t len¶

Number of bytes to be sent

const bool multicast¶

Request ACK response (false), or no ACK response (true). Be sure to have called enableDynamicAck() at least once before setting this parameter.

Returns:

• true if the payload passed to buf was loaded in the TX FIFO.

• false if the payload passed to buf was not loaded in the TX FIFO because a previous payload already in the TX FIFO failed to transmit. This condition can only be reported if the auto-ack feature is on (and the multicast parameter is set to false).

void RF24::reUseTX()¶

The function will instruct the radio to re-use the payload in the top level (first out) of the TX FIFO buffers. This is used internally by 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 calling flush_tx(). If the TX FIFO has only the one payload (in the top level), the re-used payload can be overwritten by using write(), writeFast(), writeBlocking(), startWrite(), or startFastWrite(). If the TX FIFO has other payloads enqueued, then the aforementioned functions will attempt to enqueue the a new payload in the TX FIFO (does not overwrite the top level of the TX FIFO). Currently, stopListening() also calls flush_tx() when ACK payloads are enabled (via enableAckPayload()).

Upon exiting, this function will set the CE pin HIGH to initiate the re-transmission process. If only 1 re-transmission is desired, then the CE pin should be set to LOW after the mandatory minumum pulse duration of 10 microseconds.

Remark

This function only applies when taking advantage of the auto-retry feature. See setAutoAck() and setRetries() to configure the auto-retry feature.

Note

This is to be used AFTER auto-retry fails if wanting to resend using the built-in payload reuse feature. After issuing reUseTX(), it will keep resending the same payload until a transmission failure occurs or the CE pin is set to LOW (whichever comes first). In the event of a re-transmission failure, simply call this function again to resume re-transmission of the same payload.

bool RF24::writeBlocking(const void *buf, uint8_t len, uint32_t timeout)¶

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.

Example (Full blocking):

radio.writeBlocking(&buf, sizeof(buf), 1000); // Wait up to 1 second to write 1 payload to the buffers
radio.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.

See also

• txStandBy()

• write()

• writeFast()

Note

If used from within an interrupt, the interrupt should be disabled until completion, and sei(); called to enable millis().

Note

The len parameter must be omitted when using the python wrapper because the length of the payload is determined automatically. To use this function in the python wrapper:

# let `radio` be the instantiated RF24 object
buffer = b"Hello World"  # a `bytes` object
radio.writeBlocking(buffer, 1000)  # 1000 means wait at most 1 second

Warning

It is important to never keep the nRF24L01 in TX mode and FIFO full 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.

Parameters:

const void *buf¶

Pointer to the data to be sent

uint8_t len¶

Number of bytes to be sent

uint32_t timeout¶

User defined timeout in milliseconds.

Returns:

• true if the payload passed to buf was loaded in the TX FIFO.

• false if the payload passed to buf was not loaded in the TX FIFO because a previous payload already in the TX FIFO failed to transmit. This condition can only be reported if the auto-ack feature is on.

void RF24::startFastWrite(const void *buf, uint8_t len, const bool multicast, bool startTx = 1)¶

Non-blocking write to the open writing pipe used for buffered writes

See also

• write()

• writeFast()

• startWrite()

• writeBlocking()

• setAutoAck() (for single noAck 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. Can be used as an alternative to startWrite() if writing multiple payloads at once.

Note

The len parameter must be omitted when using the python wrapper because the length of the payload is determined automatically. To use this function in the python wrapper:

# let `radio` be the instantiated RF24 object
buffer = b"Hello World"  # a `bytes` object
radio.startFastWrite(buffer, False, True)  # 3rd parameter is optional
#     False means expecting ACK response (multicast parameter)
#     True means initiate transmission (startTx parameter)

Warning

It is important to never keep the nRF24L01 in TX mode with FIFO full for more than 4ms at a time. If the auto retransmit/autoAck 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.

Parameters:

const void *buf¶

Pointer to the data to be sent

uint8_t len¶

Number of bytes to be sent

const bool multicast¶

Request ACK response (false), or no ACK response (true). Be sure to have called enableDynamicAck() at least once before setting this parameter.

bool startTx = 1¶

If this is set to true, then this function sets the nRF24L01’s CE pin to active (enabling TX transmissions). false has no effect on the nRF24L01’s CE pin and simply loads the payload into the TX FIFO.

bool RF24::startWrite(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().

See also

• write()

• writeFast()

• startFastWrite()

• whatHappened()

• setAutoAck() (for single noAck writes)

Note

The len parameter must be omitted when using the python wrapper because the length of the payload is determined automatically. To use this function in the python wrapper:

# let `radio` be the instantiated RF24 object
buffer = b"Hello World"  # a `bytes` object
radio.startWrite(buffer, False)  # False = the multicast parameter

Parameters:

const void *buf¶

Pointer to the data to be sent

uint8_t len¶

Number of bytes to be sent

const bool multicast¶

Request ACK response (false), or no ACK response (true). Be sure to have called enableDynamicAck() at least once before setting this parameter.

Returns:

• true if payload was written to the TX FIFO buffers and the transmission was started.

• false if the TX FIFO is full and the payload could not be written. In this condition, the transmission process is restarted.

bool RF24::txStandBy()¶

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.

Relies on built-in auto retry functionality.

Example (Partial blocking):

radio.writeFast(&buf, 32);
radio.writeFast(&buf, 32);
radio.writeFast(&buf, 32);   //Fills the FIFO buffers up
bool ok = radio.txStandBy(); //Returns 0 if failed. 1 if success.
                             //Blocks only until MAX_RT timeout or success. Data flushed on fail.

See also

txStandBy(uint32_t timeout, bool startTx)

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. This is not required if auto-ack is enabled.

Returns:

• true if all payloads in the TX FIFO were delivered successfully and an acknowledgement (ACK packet) was received for each. If auto-ack is disabled, then any attempt to transmit will also return true (even if the payload was not received).

• false if a payload was sent but was not acknowledged with an ACK packet. This condition can only be reported if the auto-ack feature is on.

bool RF24::txStandBy(uint32_t timeout, bool startTx = 0)¶

This function allows extended blocking and auto-retries per a user defined timeout

Fully Blocking Example:

radio.writeFast(&buf, 32);
radio.writeFast(&buf, 32);
radio.writeFast(&buf, 32);       //Fills the FIFO buffers up
bool ok = radio.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.

Note

If used from within an interrupt, the interrupt should be disabled until completion, and sei(); called to enable millis().

Parameters:

uint32_t timeout¶

Number of milliseconds to retry failed payloads

bool startTx = 0¶

If this is set to true, then this function puts the nRF24L01 in TX Mode. false leaves the primary mode (TX or RX) as it is, which can prevent the mandatory wait time to change modes.

Returns:

• true if all payloads in the TX FIFO were delivered successfully and an acknowledgement (ACK packet) was received for each. If auto-ack is disabled, then any attempt to transmit will also return true (even if the payload was not received).

• false if a payload was sent but was not acknowledged with an ACK packet. This condition can only be reported if the auto-ack feature is on.

Power Management¶

void RF24::powerDown(void)¶

Enter low-power mode

To return to normal power mode, call powerUp().

radio.powerDown();
avr_enter_sleep_mode(); // Custom function to sleep the device
radio.powerUp();

Note

After calling startListening(), a basic radio will consume about 13.5mA at max PA level. During active transmission, the radio will consume about 11.5mA, but this will be reduced to 26uA (.026mA) between sending. In full powerDown mode, the radio will consume approximately 900nA (.0009mA)

void RF24::powerUp(void)¶

Leave low-power mode - required for normal radio operation after calling powerDown()

To return to low power mode, call powerDown().

Note

This will take up to 5ms for maximum compatibility

FIFO Management¶

bool RF24::rxFifoFull()¶

Use this function to check if the radio’s RX FIFO levels are all occupied. This can be used to prevent data loss because any incoming transmissions are rejected if there is no unoccupied levels in the RX FIFO to store the incoming payload. Remember that each level can hold up to a maximum of 32 bytes.

Returns:

• true if all three 3 levels of the RX FIFO buffers are occupied.

• false if there is one or more levels available in the RX FIFO buffers. Remember that this does not always mean that the RX FIFO buffers are empty; use available() to see if the RX FIFO buffers are empty or not.

uint8_t RF24::flush_tx(void)¶

Empty all 3 of the TX (transmit) FIFO buffers. This is automatically called by stopListening() if ACK payloads are enabled. However, startListening() does not call this function.

Returns:

Current value of status register

uint8_t RF24::flush_rx(void)¶

Empty all 3 of the RX (receive) FIFO buffers.

Returns:

Current value of status register

uint8_t RF24::isFifo(bool about_tx)¶

Parameters:

bool about_tx¶

true focuses on the TX FIFO, false focuses on the RX FIFO

Returns:

• 0 if the specified FIFO is neither full nor empty.

• 1 if the specified FIFO is empty.

• 2 if the specified FIFO is full.

bool RF24::isFifo(bool about_tx, bool check_empty)¶

Parameters:

bool about_tx¶

true focuses on the TX FIFO, false focuses on the RX FIFO

bool check_empty¶

• true checks if the specified FIFO is empty

• false checks is the specified FIFO is full.

Returns:

A boolean answer to the question “is the [TX/RX] FIFO [empty/full]?”

Ambiguous Signal Detection¶

void RF24::startConstCarrier(rf24_pa_dbm_e level, uint8_t channel)¶

Transmission of constant carrier wave with defined frequency and output power

Warning

If isPVariant() returns true, then this function takes extra measures that alter some settings. These settings alterations include:

• setAutoAck() to false (for all pipes)

• setRetries() to retry 0 times with a delay of 250 microseconds

• set the TX address to 5 bytes of 0xFF

• flush_tx()

• load a 32 byte payload of 0xFF into the TX FIFO’s top level

• disableCRC()

Parameters:

rf24_pa_dbm_e level¶

Output power to use

uint8_t channel¶

The channel to use

void RF24::stopConstCarrier(void)¶

Stop transmission of constant wave and reset PLL and CONT registers

See also

startConstCarrier()

Note

If isPVariant() returns true, please remember to re-configure the radio’s settings

// re-establish default settings
setCRCLength(RF24_CRC_16);
setAutoAck(true);
setRetries(5, 15);

Warning

this function will powerDown() the radio per recommendation of datasheet.

bool RF24::testCarrier(void)¶

Test whether there was a carrier on the line for the previous listening period.

Useful to check for interference on the current channel.

Returns:

true if was carrier, false if not

bool RF24::testRPD(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.

bool goodSignal = radio.testRPD();
if(radio.available()){
   Serial.println(goodSignal ? "Strong signal > -64dBm" : "Weak signal < -64dBm" );
   radio.read(&payload,sizeof(payload));
}

Returns:

true if a signal greater than or equal to -64dBm was detected, false if not.

Configuration API¶

void RF24::setAddressWidth(uint8_t a_width)¶

Set the address width from 3 to 5 bytes (24, 32 or 40 bit)

Parameters:

uint8_t a_width¶

The address width (in bytes) to use; this can be 3, 4 or 5.

void RF24::setRetries(uint8_t delay, uint8_t count)¶

Set the number of retry attempts and delay between retry attempts when transmitting a payload. The radio is waiting for an acknowledgement (ACK) packet during the delay between retry attempts.

Note

Disable the auto-retry feature on a transmitter still uses the auto-ack feature (if enabled), except it will not retry to transmit if the payload was not acknowledged on the first attempt.

Parameters:

uint8_t delay¶

How long to wait between each retry, in multiples of 250 us. The minumum of 0 means 250 us, and the maximum of 15 means 4000 us. The default value of 5 means 1500us (5 * 250 + 250).

uint8_t count¶

How many retries before giving up. The default/maximum is 15. Use 0 to disable the auto-retry feature all together.

void RF24::maskIRQ(bool tx_ok, bool tx_fail, bool rx_ready)¶

This function is used to configure what events will trigger the Interrupt Request (IRQ) pin active LOW. The following events can be configured:

1. ”data sent”: This does not mean that the data transmitted was received, only that the attempt to send it was complete.

2. ”data failed”: This means the data being sent was not received. This event is only triggered when the auto-ack feature is enabled.

3. ”data received”: This means that data from a receiving payload has been loaded into the RX FIFO buffers. Remember that there are only 3 levels available in the RX FIFO buffers.

By default, all events are configured to trigger the IRQ pin active LOW. When the IRQ pin is active, use whatHappened() to determine what events triggered it. Remember that calling whatHappened() also clears these events’ status, and the IRQ pin will then be reset to inactive HIGH.

The following code configures the IRQ pin to only reflect the “data received” event:

radio.maskIRQ(1, 1, 0);

Parameters:

bool tx_ok¶

true ignores the “data sent” event, false reflects the “data sent” event on the IRQ pin.

bool tx_fail¶

true ignores the “data failed” event, false reflects the “data failed” event on the IRQ pin.

bool rx_ready¶

true ignores the “data received” event, false reflects the “data received” event on the IRQ pin.

void RF24::toggleAllPipes(bool isEnabled)¶

Open or close all data pipes.

This function does not alter the addresses assigned to pipes. It is simply a convenience function that allows controling all pipes at once.

Parameters:

bool isEnabled¶

true opens all pipes; false closes all pipes.

Channel (Frequency)¶

void RF24::setChannel(uint8_t channel)¶

Set RF communication channel. The frequency used by a channel is calculated as:

2400 MHz + <channel number>

Meaning the default channel of 76 uses the approximate frequency of 2476 MHz.

Note

In the python wrapper, this function is the setter of the channel attribute.To use this function in the python wrapper:

# let `radio` be the instantiated RF24 object
radio.channel = 2  # set the channel to 2 (2402 MHz)

Parameters:

uint8_t channel¶

Which RF channel to communicate on, 0-125

uint8_t RF24::getChannel(void)¶

Get RF communication channel

Note

In the python wrapper, this function is the getter of the channel attribute.To use this function in the python wrapper:

# let `radio` be the instantiated RF24 object
chn = radio.channel  # get the channel

Returns:

The currently configured RF Channel

Dynamic Delays¶

uint32_t RF24::txDelay¶

The driver will delay for this duration when stopListening() is called

When responding to payloads, faster devices like ARM(RPi) are much faster than Arduino:

1. Arduino sends data to RPi, switches to RX mode

2. The RPi receives the data, switches to TX mode and sends before the Arduino radio is in RX mode

3. If AutoACK is disabled, this can be set as low as 0. If AA/ESB enabled, set to 100uS minimum on RPi

Warning

If set to 0, ensure 130uS delay after stopListening() and before any sends

uint32_t RF24::csDelay¶

On all devices but Linux and ATTiny, a small delay is added to the CSN toggling function

This is intended to minimise the speed of SPI polling due to radio commands

If using interrupts or timed requests, this can be set to 0 Default:5

Payload Sizes¶

void RF24::setPayloadSize(uint8_t size)¶

Set Static Payload Size

This implementation uses a pre-established 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().

Note

In the python wrapper, this function is the setter of the payloadSize attribute.To use this function in the python wrapper:

# let `radio` be the instantiated RF24 object
radio.payloadSize = 16  # set the static payload size to 16 bytes

Parameters:

uint8_t size¶

The number of bytes in the payload

uint8_t RF24::getPayloadSize(void)¶

Get Static Payload Size

See also

setPayloadSize()

Note

In the python wrapper, this function is the getter of the payloadSize attribute.To use this function in the python wrapper:

# let `radio` be the instantiated RF24 object
pl_size = radio.payloadSize  # get the static payload size

Returns:

The number of bytes in the payload

void RF24::enableDynamicPayloads(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.

void RF24::disableDynamicPayloads(void)¶

Disable dynamically-sized payloads

This disables dynamic payloads on ALL pipes. Since Ack Payloads requires Dynamic Payloads, Ack Payloads are also disabled. If dynamic payloads are later re-enabled and ack payloads are desired then enableAckPayload() must be called again as well.

uint8_t RF24::getDynamicPayloadSize(void)¶

Get Dynamic Payload Size

For dynamic payloads, this pulls the size of the payload off the chip

Note

Corrupt packets are now detected and flushed per the manufacturer.

if(radio.available()){
  if(radio.getDynamicPayloadSize() < 1){
    // Corrupt payload has been flushed
    return;
  }
  radio.read(&data,sizeof(data));
}

Returns:

Payload length of last-received dynamic payload

Auto-Acknowledgement¶

void RF24::setAutoAck(bool enable)¶

Enable or disable the auto-acknowledgement feature for all pipes. This feature is enabled by default. Auto-acknowledgement responds to every received payload with an empty ACK packet. These ACK packets get sent from the receiving radio back to the transmitting radio. To attach an ACK payload to a ACK packet, use writeAckPayload().

If this feature is disabled on a transmitting radio, then the transmitting radio will always report that the payload was received (even if it was not). Please remember that this feature’s configuration needs to match for transmitting and receiving radios.

See also

• write()

• writeFast()

• startFastWrite()

• startWrite()

• writeAckPayload()

Note

If disabling auto-acknowledgment packets, the ACK payloads feature is also disabled as this feature is required to send ACK payloads.

Warning

When using the multicast parameter to write(), this feature can be disabled for an individual payload. However, if this feature is disabled, then the multicast parameter will have no effect.

Parameters:

bool enable¶

Whether to enable (true) or disable (false) the auto-acknowledgment feature for all pipes

void RF24::setAutoAck(uint8_t pipe, bool enable)¶

Enable or disable the auto-acknowledgement feature for a specific pipe. This feature is enabled by default for all pipes. Auto-acknowledgement responds to every received payload with an empty ACK packet. These ACK packets get sent from the receiving radio back to the transmitting radio. To attach an ACK payload to a ACK packet, use writeAckPayload().

Pipe 0 is used for TX operations, which include sending ACK packets. If using this feature on both TX & RX nodes, then pipe 0 must have this feature enabled for the RX & TX operations. If this feature is disabled on a transmitting radio’s pipe 0, then the transmitting radio will always report that the payload was received (even if it was not). Remember to also enable this feature for any pipe that is openly listening to a transmitting radio with this feature enabled.

See also

• write()

• writeFast()

• startFastWrite()

• startWrite()

• writeAckPayload()

• enableAckPayload()

• disableAckPayload()

Note

If disabling auto-acknowledgment packets on pipe 0, the ACK payloads feature is also disabled as this feature is required on pipe 0 to send ACK payloads.

Warning

If this feature is enabled for pipe 0, then the multicast parameter to write() can be used to disable this feature for an individual payload. However, if this feature is disabled for pipe 0, then the multicast parameter will have no effect.

Parameters:

uint8_t pipe¶

Which pipe to configure. This number should be in range [0, 5].

bool enable¶

Whether to enable (true) or disable (false) the auto-acknowledgment feature for the specified pipe

void RF24::enableAckPayload(void)¶

Enable custom payloads in the acknowledge packets

ACK payloads are a handy way to return data back to senders without manually changing the radio modes on both units.

Remark

The ACK payload feature requires the auto-ack feature to be enabled for any pipe using ACK payloads. This function does not automatically enable the auto-ack feature on pipe 0 since the auto-ack feature is enabled for all pipes by default.

See also

setAutoAck()

Note

ACK payloads are dynamic payloads. This function automatically enables dynamic payloads on pipes 0 & 1 by default. Call enableDynamicPayloads() to enable on all pipes (especially for RX nodes that use pipes other than pipe 0 to receive transmissions expecting responses with ACK payloads).

void RF24::disableAckPayload(void)¶

Disable custom payloads on the acknowledge packets

See also

enableAckPayload()

void RF24::enableDynamicAck()¶

Enable dynamic ACKs (single write multicast or unicast) for chosen messages.

radio.write(&data, 32, 1); // Sends a payload with no acknowledgement requested
radio.write(&data, 32, 0); // Sends a payload using auto-retry/autoACK

See also

• setAutoAck() for all pipes

• setAutoAck(uint8_t, bool) for individual pipes

Note

This function must be called once before using the multicast parameter for any functions that offer it. To use multicast behavior about all outgoing payloads (using pipe 0) or incoming payloads (concerning all RX pipes), use setAutoAck()

bool RF24::isAckPayloadAvailable(void)¶

Determine if an ack payload was received in the most recent call to write(). The regular available() can also be used.

Deprecated:

For compatibility with old code only, see synonymous function available(). Use read() to retrieve the ack payload and getDynamicPayloadSize() to get the ACK payload size.

Returns:

True if an ack payload is available.

Radiation Options¶

void RF24::setPALevel(uint8_t level, bool lnaEnable = 1)¶

Set Power Amplifier (PA) level and Low Noise Amplifier (LNA) state

level (enum value)	nRF24L01 description	Si24R1 description when lnaEnable = 1	Si24R1 description when lnaEnable = 0
RF24_PA_MIN (0)	-18 dBm	-6 dBm	-12 dBm
RF24_PA_LOW (1)	-12 dBm	-0 dBm	-4 dBm
RF24_PA_HIGH (2)	-6 dBm	3 dBm	1 dBm
RF24_PA_MAX (3)	0 dBm	7 dBm	4 dBm

Note

The getPALevel() function does not care what was passed lnaEnable parameter.

Parameters:

uint8_t level¶

The desired Power Amplifier level as defined by rf24_pa_dbm_e.

bool lnaEnable = 1¶

Enable or Disable the LNA (Low Noise Amplifier) Gain. See table for Si24R1 modules below. lnaEnable only affects nRF24L01 modules with an LNA chip.

uint8_t RF24::getPALevel(void)¶

Fetches the current Power Amplifier level.

Returns:

One of the values defined by rf24_pa_dbm_e. See tables in rf24_pa_dbm_e or setPALevel()

bool RF24::setDataRate(rf24_datarate_e speed)¶

Set the transmission datarate

Warning

setting RF24_250KBPS will fail for non-plus modules (when isPVariant() returns false).

Parameters:

rf24_datarate_e speed¶

Specify one of the following values (as defined by rf24_datarate_e):

speed (enum value)	description
RF24_1MBPS (0)	for 1 Mbps
RF24_2MBPS (1)	for 2 Mbps
RF24_250KBPS (2)	for 250 kbps

Returns:

true if the change was successful

rf24_datarate_e RF24::getDataRate(void)¶

Fetches the currently configured transmission datarate

Returns:

One of the values defined by rf24_datarate_e. See table in rf24_datarate_e or setDataRate()

void RF24::setRadiation(uint8_t level, rf24_datarate_e speed, bool lnaEnable = true)¶

configure the RF_SETUP register in 1 transaction

Parameters:

uint8_t level¶

This parameter is the same input as setPALevel()’s level parameter. See rf24_pa_dbm_e enum for accepted values.

rf24_datarate_e speed¶

This parameter is the same input as setDataRate()’s speed parameter. See rf24_datarate_e enum for accepted values.

bool lnaEnable = true¶

This optional parameter is the same as setPALevel()’s lnaEnable optional parameter. Defaults to true (meaning LNA feature is enabled) when not specified.

CRC Lengths¶

void RF24::setCRCLength(rf24_crclength_e length)¶

Set the CRC length (in bits)

CRC cannot be disabled if auto-ack is enabled

Parameters:

rf24_crclength_e length¶

Specify one of the values (as defined by rf24_crclength_e)

length (enum value)	description
RF24_CRC_DISABLED (0)	to disable using CRC checksums
RF24_CRC_8 (1)	to use 8-bit checksums
RF24_CRC_16 (2)	to use 16-bit checksums

rf24_crclength_e RF24::getCRCLength(void)¶

Get the CRC length (in bits)

CRC checking cannot be disabled if auto-ack is enabled

Returns:

One of the values defined by rf24_crclength_e. See table in rf24_crclength_e or setCRCLength()

void RF24::disableCRC(void)¶

Disable CRC validation

Warning

CRC cannot be disabled if auto-ack/ESB is enabled.

Protected API¶

These are the members and functions made available to derivatives that inherit from the RF24 class.

inline void RF24::beginTransaction()¶

SPI transactions

Common code for SPI transactions including CSN toggle

inline void RF24::endTransaction()¶

uint8_t RF24::read_register(uint8_t reg)¶

Read single byte from a register

Parameters:

uint8_t reg¶

Which register. Use constants from nRF24L01.h

Returns:

Current value of register reg

void RF24::read_register(uint8_t reg, uint8_t *buf, uint8_t len)¶

Read a chunk of data in from a register

Note

This returns nothing. Older versions of this function returned the status byte, but that it now saved to a private member on all SPI transactions.

Parameters:

uint8_t reg¶

Which register. Use constants from nRF24L01.h

uint8_t *buf¶

[out] Where to put the data

uint8_t len¶

How many bytes of data to transfer

bool RF24::ack_payloads_enabled¶

Whether ack payloads are enabled.

uint8_t RF24::addr_width¶

The address width to use (3, 4 or 5 bytes).

bool RF24::dynamic_payloads_enabled¶

Whether dynamic payloads are enabled.