NRF24L01P-R datasheet(29/78 Pages) NORDIC

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nRF24L01+ Product Specification

7.3.3.1

Payload length

This 6 bit field specifies the length of the payload in bytes. The length of the payload can be from 0 to 32

bytes.

Coding: 000000 = 0 byte (only used in empty ACK packets.) 100000 = 32 byte, 100001 = Don’t care.

This field is only used if the Dynamic Payload Length function is enabled.

7.3.3.2

PID (Packet identification)

The 2 bit PID field is used to detect if the received packet is new or retransmitted. PID prevents the PRX

device from presenting the same payload more than once to the receiving host MCU. The PID field is

incremented at the TX side for each new packet received through the SPI. The PID and CRC fields (see

section 7.3.5 on page 30) are used by the PRX device to determine if a packet is retransmitted or new.

When several data packets are lost on the link, the PID fields may become equal to the last received PID.

If a packet has the same PID as the previous packet, nRF24L01+ compares the CRC sums from both

packets. If the CRC sums are also equal, the last received packet is considered a copy of the previously

received packet and discarded.

7.3.3.3

No Acknowledgment flag (NO_ACK)

The Selective Auto Acknowledgement feature controls the NO_ACK flag.

This flag is only used when the auto acknowledgement feature is used. Setting the flag high tells the

receiver that the packet is not to be auto acknowledged.

On the PTX you can set the NO_ACK flag bit in the Packet Control Field with this command:

W_TX_PAYLOAD_NOACK

However, the function must first be enabled in the FEATURE register by setting the EN_DYN_ACK bit.

When you use this option the PTX goes directly to standby-I mode after transmitting the packet. The PRX

does not transmit an ACK packet when it receives the packet.

7.3.4

Payload

The payload is the user defined content of the packet. It can be 0 to 32 bytes wide and is transmitted on-air

when it is uploaded to nRF24L01+.

Enhanced ShockBurst™ provides two alternatives for handling payload lengths; static and dynamic.

The default is static payload length. With static payload length all packets between a transmitter and a

receiver have the same length. Static payload length is set by the RX_PW_Px registers on the receiver side.

The payload length on the transmitter side is set by the number of bytes clocked into the TX_FIFO and

must equal the value in the RX_PW_Px register on the receiver side.

Dynamic Payload Length (DPL) is an alternative to static payload length. DPL enables the transmitter to

send packets with variable payload length to the receiver. This means that for a system with different pay-

load lengths it is not necessary to scale the packet length to the longest payload.

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