Advanced API¶
what_happened()¶
-
RF24.
what_happened
(dump_pipes=False)[source]¶ This debuggung function aggregates and outputs all status/condition related information from the nRF24L01.
Some information may be irrelevant depending on nRF24L01’s state/condition.
Prints: Is a plus variant
True means the transceiver is a nRF24L01+. False means the transceiver is a nRF24L01 (not a plus variant).Channel
The current setting of thechannel
attributeRF Data Rate
The current setting of the RFdata_rate
attribute.RF Power Amplifier
The current setting of thepa_level
attribute.CRC bytes
The current setting of thecrc
attributeAddress length
The current setting of theaddress_length
attributeTX Payload lengths
The current setting of thepayload_length
attribute for TX operations (concerning data pipe 0)Auto retry delay
The current setting of theard
attributeAuto retry attempts
The current setting of thearc
attributeRe-use TX FIFO
Are payloads in the TX FIFO to be re-used for subsequent transmissions (triggered by callingresend()
)Packets lost on current channel
Total amount of packets lost (transmission failures). This only resets when thechannel
is changed. This count will only go up to 15.Retry attempts made for last transmission
Amount of attempts to re-transmit during last transmission (resets per payload)IRQ - Data Ready
The current setting of the IRQ pin on “Data Ready” eventIRQ - Data Sent
The current setting of the IRQ pin on “Data Sent” eventIRQ - Data Fail
The current setting of the IRQ pin on “Data Fail” eventData Ready
Is there RX data ready to be read? (state of theirq_dr
flag)Data Sent
Has the TX data been sent? (state of theirq_ds
flag)Data Failed
Has the maximum attempts to re-transmit been reached? (state of theirq_df
flag)TX FIFO full
Is the TX FIFO buffer full? (state of thetx_full
flag)TX FIFO empty
Is the TX FIFO buffer empty?RX FIFO full
Is the RX FIFO buffer full?RX FIFO empty
Is the RX FIFO buffer empty?Custom ACK payload
Is the nRF24L01 setup to use an extra (user defined) payload attached to the acknowledgment packet? (state of theack
attribute)Ask no ACK
Is the nRF24L01 setup to transmit individual packets that don’t require acknowledgment?Automatic Acknowledgment
The status of theauto_ack
feature. If this value is a binary representation, then each bit represents the feature’s status for each pipe.Dynamic Payloads
The status of thedynamic_payloads
feature. If this value is a binary representation, then each bit represents the feature’s status for each pipe.Primary Mode
The current mode (RX or TX) of communication of the nRF24L01 device.Power Mode
The power state can be Off, Standby-I, Standby-II, or On.
Parameters: dump_pipes (bool) –
True
appends the output and prints:- the current address used for TX transmissions. This value is the entire content of
the nRF24L01’s register about the TX address (despite what
address_length
is set to). Pipe [#] ([open/closed]) bound: [address]
where#
represent the pipe number, theopen/closed
status is relative to the pipe’s RX status, andaddress
is the full value stored in the nRF24L01’s RX address registers (despite whataddress_length
is set to.- if the pipe is open, then the output also prints
expecting [X] byte static payloads
whereX
is thepayload_length
(in bytes) the pipe is setup to receive whendynamic_payloads
is disabled for that pipe.
This parameter’s default is
False
and skips this extra information.
is_plus_variant¶
load_ack()¶
-
RF24.
load_ack
(buf, pipe_number)[source]¶ This allows the MCU to specify a payload to be allocated into the TX FIFO buffer for use on a specific data pipe.
This payload will then be appended to the automatic acknowledgment (ACK) packet that is sent when new data is received on the specified pipe. See
recv()
on how to fetch a received custom ACK payloads.Parameters: - buf (bytearray,bytes) – This will be the data attached to an automatic ACK packet on the
incoming transmission about the specified
pipe_number
parameter. This must have a length in range [1, 32] bytes, otherwise aValueError
exception is thrown. Any ACK payloads will remain in the TX FIFO buffer until transmitted successfully orflush_tx()
is called. - pipe_number (int) – This will be the pipe number to use for deciding which
transmissions get a response with the specified
buf
parameter’s data. This number must be in range [0, 5], otherwise aIndexError
exception is thrown.
Returns: True
if payload was successfully loaded onto the TX FIFO buffer.False
if it wasn’t because TX FIFO buffer is full.Note
this function takes advantage of a special feature on the nRF24L01 and needs to be called for every time a customized ACK payload is to be used (not for every automatic ACK packet – this just appends a payload to the ACK packet). The
ack
,auto_ack
, anddynamic_payloads
attributes are also automatically enabled (with respect to data pipe 0) by this function when necessary.Tip
The ACK payload must be set prior to receiving a transmission. It is also worth noting that the nRF24L01 can hold up to 3 ACK payloads pending transmission. Using this function does not over-write existing ACK payloads pending; it only adds to the queue (TX FIFO buffer) if it can. Use
flush_tx()
to discard unused ACK payloads when done listening.- buf (bytearray,bytes) – This will be the data attached to an automatic ACK packet on the
incoming transmission about the specified
read_ack()¶
irq_dr¶
-
RF24.
irq_dr
¶ A
bool
that represents the “Data Ready” interrupted flag. (read-only) .Returns: Pass
data_recv
parameter asTrue
toclear_status_flags()
and reset this. As this is a virtual representation of the interrupt event, this attribute will always be updated despite what the actual IRQ pin is configured to do about this event.Calling this does not execute an SPI transaction. It only exposes that latest data contained in the STATUS byte that’s always returned from any other SPI transactions. Use the
update()
function to manually refresh this data when needed (especially after callingclear_status_flags()
).
irq_df¶
-
RF24.
irq_df
¶ A
bool
that represents the “Data Failed” interrupted flag. (read-only) .Returns: Pass
data_fail
parameter asTrue
toclear_status_flags()
and reset this. As this is a virtual representation of the interrupt event, this attribute will always be updated despite what the actual IRQ pin is configured to do about this event.Calling this does not execute an SPI transaction. It only exposes that latest data contained in the STATUS byte that’s always returned from any other SPI transactions. Use the
update()
function to manually refresh this data when needed (especially after callingclear_status_flags()
).
irq_ds¶
-
RF24.
irq_ds
¶ A
bool
that represents the “Data Sent” interrupted flag. (read-only) .Returns: Pass
data_sent
parameter asTrue
toclear_status_flags()
and reset this. As this is a virtual representation of the interrupt event, this attribute will always be updated despite what the actual IRQ pin is configured to do about this event.Calling this does not execute an SPI transaction. It only exposes that latest data contained in the STATUS byte that’s always returned from any other SPI transactions. Use the
update()
function to manually refresh this data when needed (especially after callingclear_status_flags()
).
clear_status_flags()¶
-
RF24.
clear_status_flags
(data_recv=True, data_sent=True, data_fail=True)[source]¶ This clears the interrupt flags in the status register.
Internally, this is automatically called by
send()
,write()
,recv()
, and whenlisten
changes fromFalse
toTrue
.Parameters: Note
Clearing the
data_fail
flag is necessary for continued transmissions from the nRF24L01 (locks the TX FIFO buffer whenirq_df
isTrue
) despite wheather or not the MCU is taking advantage of the interrupt (IRQ) pin. Call this function only when there is an antiquated status flag (after you’ve dealt with the specific payload related to the staus flags that were set), otherwise it can cause payloads to be ignored and occupy the RX/TX FIFO buffers. See Appendix A of the nRF24L01+ Specifications Sheet for an outline of proper behavior.
power¶
-
RF24.
power
¶ This
bool
attribute controls the power state of the nRF24L01. This is exposed for convenience.False
basically puts the nRF24L01 to sleep (AKA power down mode) with ultra-low current consumption. No transmissions are executed when sleeping, but the nRF24L01 can still be accessed through SPI. Upon instantiation, this driver class puts the nRF24L01 to sleep until the MCU invokes RX/TX modes. This driver class will only power down the nRF24L01 after exiting aThe with statement
block.True
powers up the nRF24L01. This is the first step towards entering RX/TX modes (see alsolisten
attribute). Powering up is automatically handled by thelisten
attribute as well as thesend()
andwrite()
functions.
Note
This attribute needs to be
True
if you want to put radio on Standby-II (highest current consumption) or Standby-I (moderate current consumption) modes. The state of the CE pin determines which Standby mode is acheived. See Chapter 6.1.2-7 of the nRF24L01+ Specifications Sheet for more details.
tx_full¶
-
RF24.
tx_full
¶ An attribute to represent the nRF24L01’s status flag signaling that the TX FIFO buffer is full. (read-only) .
Calling this does not execute an SPI transaction. It only exposes that latest data contained in the STATUS byte that’s always returned from any other SPI transactions. Use the
update()
function to manually refresh this data when needed (especially after callingflush_tx()
).Returns:
update()¶
-
RF24.
update
()[source]¶ This function is only used to get an updated status byte over SPI from the nRF24L01.
Refreshing the status byte is vital to checking status of the interrupt flags, RX pipe number related to current RX payload, and if the TX FIFO buffer is full. This function returns nothing, but internally updates the
irq_dr
,irq_ds
,irq_df
,pipe
, andtx_full
attributes. Internally this is a helper function tosend()
, andresend()
functions.Returns: True
for every call. This value is meant to allow this function to be used inif
statements in conjunction with attributes related to the refreshed status byte.# let ``nrf`` be the instantiated object of the RF24 class # the following if statement is faster than using ``if nrf.any():`` if nrf.update() and nrf.pipe is not None: nrf.recv()
resend()¶
-
RF24.
resend
(send_only=False)[source]¶ Use this function to maunally re-send the previous payload in the top level (first out) of the TX FIFO buffer.
This function is meant to be used for payloads that failed to transmit using the
send()
function. If a payload failed to transmit using thewrite()
function, just callclear_status_flags()
and re-start the pulse on the nRF24L01’s CE pin.Returns: Data returned from this function follows the same pattern that send()
returns with the added condition that this function will returnFalse
if the TX FIFO buffer is empty.Parameters: send_only (bool) – This parameter only applies when the ack
attribute is set toTrue
. Pass this parameter asTrue
if the RX FIFO is not to be manipulated. Many other libraries’ behave as though this parameter isTrue
(e.g. The popular TMRh20 Arduino RF24 library). This parameter defaults toFalse
. Userecv()
to get the ACK payload (if there is any) from the RX FIFO. Remember that the RX FIFO can only hold up to 3 payloads at once.Note
The nRF24L01 normally removes a payload from the TX FIFO buffer after successful transmission, but not when this function is called. The payload (successfully transmitted or not) will remain in the TX FIFO buffer until
flush_tx()
is called to remove them. Alternatively, using this function also allows the failed payload to be over-written by usingsend()
orwrite()
to load a new payload into the TX FIFO buffer.
write()¶
-
RF24.
write
(buf, ask_no_ack=False, write_only=False)[source]¶ This non-blocking function (when used as alternative to
send()
) is meant for asynchronous applications and can only handle one payload at a time as it is a helper function tosend()
.This function isn’t completely non-blocking as we still need to wait 5 ms (
CSN_DELAY
) for the CSN pin to settle (allowing an accurate SPI write transaction). Example usage of this function can be seen in the IRQ pin example and in the Stream example’s “master_fifo()” functionReturns: True
if the payload was added to the TX FIFO buffer.False
if the TX FIFO buffer is already full, and no payload could be added to it.Parameters: - buf (bytearray) –
The payload to transmit. This bytearray must have a length greater than 0 and less than 32 bytes, otherwise a
ValueError
exception is thrown.- If the
dynamic_payloads
attribute is disabled for data pipe 0 and this bytearray’s length is less than thepayload_length
attribute for data pipe 0, then this bytearray is padded with zeros until its length is equal to thepayload_length
attribute for data pipe 0. - If the
dynamic_payloads
attribute is disabled for data pipe 0 and this bytearray’s length is greater thanpayload_length
attribute for data pipe 0, then this bytearray’s length is truncated to equal thepayload_length
attribute for data pipe 0.
- If the
- ask_no_ack (bool) –
Pass this parameter as
True
to tell the nRF24L01 not to wait for an acknowledgment from the receiving nRF24L01. This parameter directly controls aNO_ACK
flag in the transmission’s Packet Control Field (9 bits of information about the payload). Therefore, it takes advantage of an nRF24L01 feature specific to individual payloads, and its value is not saved anywhere. You do not need to specify this for every payload if thearc
attribute is disabled, however setting this parameter toTrue
will work despite thearc
attribute’s setting.Note
Each transmission is in the form of a packet. This packet contains sections of data around and including the payload. See Chapter 7.3 in the nRF24L01 Specifications Sheet for more details.
- write_only (bool) –
This function will not manipulate the nRF24L01’s CE pin if this parameter is
True
. The default value ofFalse
will ensure that the CE pin is HIGH upon exiting this function. This function does not set the CE pin LOW at any time. Use this parameter asTrue
to fill the TX FIFO buffer before beginning transmissions.Note
The nRF24L01 doesn’t initiate sending until a mandatory minimum 10 µs pulse on the CE pin is acheived. If the
write_only
parameter isFalse
, then that pulse is initiated before this function exits. However, we have left that 10 µs wait time to be managed by the MCU in cases of asychronous application, or it is managed by usingsend()
instead of this function. According to the Specification sheet, if the CE pin remains HIGH for longer than 10 µs, then the nRF24L01 will continue to transmit all payloads found in the TX FIFO buffer.
Warning
A note paraphrased from the nRF24L01+ Specifications Sheet:
It is important to NEVER to keep the nRF24L01+ in TX mode for more than 4 ms at a time. If the [
arc
attribute is] enabled, nRF24L01+ is never in TX mode longer than 4 ms.Tip
Use this function at your own risk. Because of the underlying “Enhanced ShockBurst Protocol”, disobeying the 4 ms rule is easily avoided if the
arc
attribute is greater than0
. Alternatively, you MUST use nRF24L01’s IRQ pin and/or user-defined timer(s) to AVOID breaking the 4 ms rule. If the nRF24L01+ Specifications Sheet explicitly states this, we have to assume radio damage or misbehavior as a result of disobeying the 4 ms rule. See also table 18 in the nRF24L01 specification sheet for calculating an adequate transmission timeout sentinal.- buf (bytearray) –
flush_rx()¶
-
RF24.
flush_rx
()[source]¶ A helper function to flush the nRF24L01’s RX FIFO buffer.
Note
The nRF24L01 RX FIFO is 3 level stack that holds payload data. This means that there can be up to 3 received payloads (each of a maximum length equal to 32 bytes) waiting to be read (and removed from the stack) by
recv()
orread_ack()
. This function clears all 3 levels.
flush_tx()¶
-
RF24.
flush_tx
()[source]¶ A helper function to flush the nRF24L01’s TX FIFO buffer.
Note
The nRF24L01 TX FIFO is 3 level stack that holds payload data. This means that there can be up to 3 payloads (each of a maximum length equal to 32 bytes) waiting to be transmit by
send()
,resend()
orwrite()
. This function clears all 3 levels. It is worth noting that the payload data is only removed from the TX FIFO stack upon successful transmission (see alsoresend()
as the handling of failed transmissions can be altered).
fifo()¶
-
RF24.
fifo
(about_tx=False, check_empty=None)[source]¶ This provides some precision determining the status of the TX/RX FIFO buffers. (read-only)
Parameters: Returns: A
bool
answer to the question:”Is the [TX/RX](
about_tx
) FIFO buffer [empty/full](check_empty
)?If the
check_empty
parameter is not specified: anint
in range [0,2] for which:1
means the specified FIFO buffer is empty2
means the specified FIFO buffer is full0
means the specified FIFO buffer is neither full nor empty
pipe¶
-
RF24.
pipe
¶ The identifying number of the data pipe that received the next available payload in the RX FIFO buffer. (read only) .
Calling this does not execute an SPI transaction. It only exposes that latest data contained in the STATUS byte that’s always returned from any other SPI transactions. Use the
update()
function to manually refresh this data when needed (especially after callingflush_rx()
).Returns:
address_length¶
-
RF24.
address_length
¶ This
int
attribute specifies the length (in bytes) of addresses to be used for RX/TX pipes. A valid input value must be anint
in range [3, 5]. Otherwise aValueError
exception is thrown. Default is set to the nRF24L01’s maximum of 5.
address()¶
-
RF24.
address
(index=-1)[source]¶ Returns the current address set to a specified data pipe or the TX address. (read-only)
This function returns the full content of the nRF24L01’s registers about RX/TX addresses despite what
address_length
is set to.Parameters: index (int) – the number of the data pipe whose address is to be returned. A valid index ranges [0,5] for RX addresses or any negative number for the TX address. Otherwise an IndexError
is thown. This parameter defaults to-1
.
rpd¶
-
RF24.
rpd
¶ This read-only attribute returns
True
if RPD (Received Power Detector) is triggered orFalse
if not triggered. The RPD flag is triggered in the following cases:Note
See also section 6.4 of the Specification Sheet concerning the RPD flag. Ambient temperature affects the -64 dBm threshold. The latching of this flag happens differently under certain conditions.
start_carrier_wave()¶
-
RF24.
start_carrier_wave
()[source]¶ Starts a continuous carrier wave test.
This is a basic test of the nRF24L01’s TX output. It is a commonly required test for telecommunication regulations. Calling this function may introduce interference with other transceivers that use frequencies in range [2.4, 2.525] GHz. To verify that this test is working properly, use the following code on a seperate nRF24L01 transceiver:
# declare objects for SPI bus and CSN pin and CE pin nrf. = RF24(spi, csn, ce) # set nrf.pa_level, nrf.channel, & nrf.data_rate values to # match the corresponding attributes on the device that is # transmitting the carrier wave nrf.listen = True if nrf.rpd: print("carrier wave detected")
The
pa_level
,channel
&data_rate
attributes are vital factors to the success of this test. Be sure these attributes are set to the desired test conditions before calling this function. See also therpd
attribute.Note
To preserve backward compatibility with non-plus variants of the nRF24L01, this function will also change certain settings if
is_plus_variant
isFalse
. These settings changes include disablingcrc
, disablingauto_ack
, disablingarc
, settingard
to 250 microseconds, changing the TX address tob"\xFF\xFF\xFF\xFF\xFF"
, and loading a 32-byte payload (each byte is0xFF
) into the TX FIFO buffer while continuously behaving likeresend()
to establish the constant carrier wave. Ifis_plus_variant
isTrue
, then none of these changes are needed nor applied.
stop_carrier_wave()¶
-
RF24.
stop_carrier_wave
()[source]¶ Stops a continuous carrier wave test.
See
start_carrier_wave()
for more details.Note
Calling this function puts the nRF24L01 to sleep (AKA power down mode).