https://devzone.nordicsemi.com/f/nordic-q-a/3885/can-t-get-tx_ds-interrupt-on-prx-side-ack-payloadHi, I have some problem. My code was working and everything was fine, but I decided to improve my program. I made some changes, and now TX_DS interrupt on PRX side doesn&#39;t fire. :( From the beginning: PTX side: this side is sending some packeten-USTelligent Community 13Mon, 13 Oct 2014 08:24:12 GMThttps://devzone.nordicsemi.com/thread/13966?ContentTypeID=1Mon, 13 Oct 2014 08:24:12 GMT137ad170-7792-4731-bb38-c0d22fbe4515:8b4d1c57-c1d7-419d-86df-6d87e8ae5c47Asbj&#248;rn<p>Usually when you don&#39;t see a TX_DS or RX_DR interrupt it either isn&#39;t received/sent at all or the payload is static and the receiver of either the original packet or the ACK discard the payload as re-transmit. Add a counter byte to the payload to make sure the payload isn&#39;t static.</p> <p>Make sure that the original packet/ACK is actually sent by monitoring the VDD_PA pin on the nRF24L01+. This pin will go up to 1.8 V for as long as the chip is in TX mode. So you should see it rise to 1.8 V on both the PTX and PRX. See if they match up and the pattern makes sense.</p> <p>Could it be that during the writing of a new ACK payload you get interrupted by a new incoming packet and hence never complete writing the ACK payload? You could verify this by delaying the TX operation on the PTX, at least for testing.</p><div style="clear:both;"></div>