nRF52832: Switching frequency leads to unpredicted behaviour

[Lukas Krupp]

Hello everyone,

I experienced some weird behaviour with nRF52832 on the nRF52 DK when transmitting packets on different frequencies. If I switch e.g. between frequency channel 72 (2.472 GHz) and channel 5 (2.405 GHz) and let another nRF52832 listen on channel 69 (2.469 GHz) it seems to receive a packet although there should not be anything on this channel. Does anyone have an idea why this happens? 

Thank you in advance.

Best regards,

Lukas

[run_ar]

Adjacent channels are not completely blocked by the receiver. Depending on which frequencies the de-modulator operates on you could receive a signal that is sent on another channel than the one your receiver is dialed to, which is what seems to be happening in this case.

Update: Can you confirm how you receive the packet? Are you measuring the RSSI? Do you get an address match? is the CRC ok?

[Lukas Krupp]

Thank you for your answer.

The packet reception is basically realized like in the ESB protocol. Even the address is the same.

I receive an address match and the CRC is right too.

But: I just noticed, that the corresponding RSSI values of the wrong receptions clearly differ from those on the right frequencies. I can use this knowledge to sort the wrong packets out.

[run_ar]

Did you try to transmitt on only channel 72 or only channel 5? Did you still receives a packet on channel 69?

[Lukas Krupp]

Yes, I tried transmitting on only one of the two channels. Nothing was received on channel 69. So it must be the switching which causes this issue.

[run_ar]

Thanks, can you confirm which channel you tried this with? Only 5, Only 72 or both? I have to admit it sounds like this is an issue with your Software, I have not heard of any issues like this with HW so that would be quite surprising.