Data Sheet

Revision 2.0 Page 27 of 74
nRF24L01 Product Specification
With DPL feature the nRF24L01 can decode the payload length of the received packet automatically
instead of using the RX_PW_Px registers. The MCU can read the length of the received payload by using
the R_RX_PL_WID command.
In order to enable DPL the EN_DPL bit in the FEATURE register must be set. In RX mode the DYNPD reg-
ister has to be set. A PTX that transmits to a PRX with DPL enabled must have the DPL_P0 bit in DYNPD
set.
7.4.2 Automatic packet assembly
The automatic packet assembly assembles the preamble, address, packet control field, payload and CRC
to make a complete packet before it is transmitted.
7.4.2.1 Preamble
The preamble is automaticly generated based on the address field.
7.4.2.2 Address
The address is fetched from the TX_ADDR register. The address field can be configured to be 3, 4 or 5
bytes long with the AW register.
7.4.2.3 Packet control field
For the static packet lenght option the payload length field is not used. With DPL enabled, the value in the
payload length field is automaticly set to the number of bytes in the payload clocked into the TX FIFO.
The transmitter increments the PID field each time it generates a new packet and uses the same PID on
packets that are retransmitted. Refer to the left flow chart in Figure 6. on page 28
The PTX 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 and the
PRX does not transmit an ACK packet when it receives the packet.
7.4.2.4 Payload
The payload is fetched from the TX FIFO.
7.4.2.5 CRC
The CRC is automaticly calculated based on the packet content with the polynomials in 7.3.5 on page 26.
The number of bytes in the CRC is set by the CRCO bit in the CONFIG register.
7.4.3 Automatic packet validation
Enhanced ShockBurst™ features automatic packet validation. In receive mode the nRF24L01 is constanly
searching for a valid address (given in the RX_ADDR registers.) If a valid address is detected the
Enhanched ShockBurst™ will start to validate the packet.