Why am I getting no ACKs from an nRF24L01p in PRx mode?

[JimR]

Hi folks, I'm making progress with a program to get two nRF24L01p modules communicating with each other, but there are a couple of remaining problems. I hope someone can help with them, please:

1. The PTX module seems to be transmitting my 3-byte payloads correctly, and the VDD_PA pin on that nRF24L01p pulses high (~2.0V) as expected. The PRX module even reports that it is receiving most packets from the PTX module (often 6 packets in a sequence, but then there's a 'timeout' reported). BUT the PRX module never seems to be sending back an ACK, and the PTX module consequently reports that no ACK has been received. The VDD_PA pin on the PRX chip never pulses high, either -- presumably because no ACK is being sent. Can anyone suggest what I'm doing wrong?
2. I'm puzzled as to why the PRX module reports that 6 successive packets have been received successfully, but then reports a timeout with no packet received. Then it will report that the next 6 packets were received, before reporting another timeout + no packet received. And so on. This sounds a bit like some sort of timing problem, but I can't work out exactly what. Any suggestions? Thanks, JimR

[ovrebekk]

Hi Jim

The one law of nature that you must abide by is that when either kit is in PTX mode RX_ADDR_P0 and TX_ADDR has to be the same. Otherwise the ACK's will never be received, and the PTX will assume that the PRX didn't receive anything.

I think the easiest way to do what you want is to simply set TX_ADDR and RX_ADDR_P0 on both sides to E7E7E7E7E7.

Using the same code for both devices can be a bit tricky, as you have to be careful with the timing when switching from PTX to PRX mode or vice versa. Are you planning to switch between PTX and PRX dynamically as the devices are running, or just once during startup?

Best regards
Torbjørn

[JimR]

Hi Torbjorn,

Thanks for that further explanation. All is working well now, thanks to your help. Best Regards, JimR