https://devzone.nordicsemi.com/f/nordic-q-a/13331/esb-repeat-ack-payloadHi, I haven&#39;t been able to find a clear answer to this. With the ESB protocol, a payload can be stored in the PRX TX FIFO to be sent back to the PTX as part of the ACK. The way I read the documentation, that payload is then assumed to have arriveden-USTelligent Community 13Wed, 20 Apr 2016 12:48:23 GMThttps://devzone.nordicsemi.com/thread/50815?ContentTypeID=1Wed, 20 Apr 2016 12:48:23 GMT137ad170-7792-4731-bb38-c0d22fbe4515:9859e060-0a4e-490f-8b04-ffb1d6695fc6Steve H<p>Thanks, Kenneth, I&#39;m clear about it now.</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/50817?ContentTypeID=1Wed, 20 Apr 2016 12:30:13 GMT137ad170-7792-4731-bb38-c0d22fbe4515:3a72d456-86e1-4d27-a149-8b6c4e536c19Kenneth<p>Each time yes.</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/50816?ContentTypeID=1Wed, 20 Apr 2016 11:21:10 GMT137ad170-7792-4731-bb38-c0d22fbe4515:5836e307-b0d4-49e1-96ed-ff8609255358Steve H<p>Thanks, Kenneth. Does the retransmitted ACK packet include the payload each time? The documentation seemed to suggest that the payload was deleted from the PRX FIFO with the first ACK transmission.</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/50814?ContentTypeID=1Wed, 20 Apr 2016 10:28:41 GMT137ad170-7792-4731-bb38-c0d22fbe4515:934608da-6ab9-43af-a215-58b1526fe666Kenneth<p>Hi, There is a PID (packet identifier) field in all packets, so the ESB protocol ensure that an ACK packet from the PRX is sent (and retransmitted) until the PID is updated from the PTX (indicating a new packet, and not a retransmit).</p><div style="clear:both;"></div>