RSSI measurement on a specific channel

RE: RSSI measurement on a specific channel

Simonr — Thu, 25 Mar 2021 14:13:11 GMT

That depends on your project settings, but by default, nrf_radio_frequency_set is used to set the radio frequency in MHz.

Best regards,

Simon

RE: RSSI measurement on a specific channel

M. David. — Thu, 25 Mar 2021 09:40:49 GMT

What I've seen from the nrf_radio_frequency_set function, it sets the RF_RADIO->FREQUENCY register to a delta value of the provided frequency minus 2400.

If I provide 2480 for Channel 39 the register is set to 80.

Would this mean if I want to set the register directly, I'd have to write the following values to the register to set it to channel 39 or channel 37?

RF_RADIO->FREQUENCY = 80u; //Channel 39
RF_RADIO->FREQUENCY = 2u;  //Channel 37

RE: RSSI measurement on a specific channel

Simonr — Thu, 25 Mar 2021 07:19:06 GMT

Please note that the frequency for channels 37, 38, and 39 are not 2437, 2438, and 2439. The BLE system operates on 40 channels from 2402 to 2480 each being 2MHz wide. The advertising channels are strategically placed at these values to avoid interference from each other and other devices operating in the same spectrum.

I would suggest using the nrf_radio_frequency_set if you'd like to advertise on one specific frequency, but writing straight to the registers should work as well. The frequency for channel 37 would be 2402MHz.

Best regards,

Simon

RE: RSSI measurement on a specific channel

M. David. — Wed, 24 Mar 2021 14:58:15 GMT

Hi Simon

thank you for your response..

The DTM example I've already been looking at, however its hard to deceipher what command in the end is provided to the dtm_cmd(...) function.

I'm not sure if you had a look at the code I've provided in the original question, but there I can nowhere see where to set the channle/frequency. Could you point me a bit to a closer location in the DTM example where to look at?

My goal is to read the RSSI value of channel 37.

Another approach I've tried was, using the radio_test example as a basis, but there it seems not to be possible to measure an RSSI value.

EDIT:

I've just found out that you can also set the radio frequency like this:

NRF_RADIO->FREQUENCY = 2400 + 39;

So in order to measure the RSSI on channel 39, would this do the trick? By setting the frequency before enabling the radio?

RE: RSSI measurement on a specific channel

Simonr — Wed, 24 Mar 2021 13:27:28 GMT

Hi Samuel

Yes, it should be possible to get the RSSI only from one specific channel, but you would have to implement the logic to do so where you only request the RSSI from I.E. Channel 37 and not theother channels.

If you check out the DTM example we have as well as the DTM app in nRFConnect for Desktop, you can see that it has handled this in the central application where you either set it to retrieve the RSSI value of either a selected "sweep" of channels or just a single one.

Best regards,

Simon