NRF52 - ESB - Receiving duplicate packets

[nordicfreak]

We are having some issues with ESB, it seems the automatic ACKs are not working properly and we get spammed with a lot of duplicates.

We believe the issue is because we start some function immediately when NRF_ESB_EVENT_RX_RECEIVED is triggered and because of this it doesn't have time to send an ACK.

How can we delay without blocking the CPU before starting our function?

This seems to work but is it the best way?

//event triggered

for(int i=0; i<50; i++){
nrf_delay_us(10);
}

//start function

[Kenneth]

Hello,

Typically the ESB run on relative high priority, so even if the application may be executing code with lower priority it should not affect the ESB libray handle the transmisson of acknowledgements. 

If you have enabled ack you should allow sufficient time (e.g 500us) on reception of packet to ensure ack can be sent out. If you don't care about ack, it is possible to disable ack when transmitting the packet.

Kenneth

[nordicfreak]

Hi,

I added a 1ms delay before processing the RX events, and I still get duplicates

[Kenneth]

It's a bit hard to just to look at some code snippets and provide good comments, so I suggest to go back to the default ESB example and see if you have overlooked anything. Maybe you did one change at a certain point that started triggering this in specific. For instance does removing nrf_esb_flush_rx() from NRF_ESB_EVENT_RX_RECEIVED change anything?

Kenneth

[nordicfreak]

Thanks for the reply Kenneth.

I removed nrf_esb_flush_rx() and it exhibits the same behavior.

Does the TX function and the RX handler look ok to you?

[Kenneth]

I am not entirely sure I understand your tx, it seems the chunk_size is 32bytes, but you are only sending 21bytes? Are you sure you are not just sending the start of the *data array several times? How do you ensure len is not larger than 32bytes? Does nrf_esb_write_payload() return any error?

Edit: Wait a sec, are you calling esb_tx() several times here with the same packet (that is 21bytes)? Is that the duplicate you see?

Kenneth

[nordicfreak]

It's a while loop that sends data in chunks of max 32 bytes, until there is no more data left.

esb_tx is called only one time, and apparently got no ack because it failed, but still the data managed to get to the other side.

The question here is, why is the handler raised several times when esb should prevent duplicates at a lower level?

[Kenneth]

But is it not kind of weired that you are only seeing duplicates of the last(?) 21byte packet, and not any of the 32byte packets? FYI: If the same packet is written several times, it will be received several times.

Kenneth

[nordicfreak]

As you can see i receive duplicates of the first 21 byte packet that i send. This causes some malfunctions and that's why you see the 2 bytes ones also.

The question is why is the 21 packet arriving 2 times if i only call the function one time, and if you check the TX output you see it's sent one time and it fails

[Kenneth]

What nRF device is the RX and is it a DK?

Kenneth

[nordicfreak]

RX is 52832 DK