NRF21540 Shield + NRF52833 DK - lower RSSI with shield than without

[lbe]

Good morning everyone,

I need to develop a firmware for a custom board that features an NRF21540 + NRF52833.

I started the development using the official evaluation kits: an NRF52833 DK + the NRF21540 shield.

I started from the example BLE peripheral "nrf_uart", which I compiled for the board nrf52833_nrf52833 and to which I added the -DSHIELD=nrf21540_ek

as indicated in the section "Working with FEM". I used two SMA 2.4GHz antenna with the nrf21540_ek and I used the nrf_connect smartphone app to

record the RSSI of the advertising.

It turned out that if I use the 21540 shield, I got a slightly worse RSSI than if not using the shield (I created a separate build configuration without using the -DSHIELD option).

I have about -55dBm without shield (about 1mt distance) and between -60 and -65dBm with the shield.

Clearly, I put the board and my smartphone in the same conditions and distance.

So, apparently, the 21540 is not used or worst, is badly affecting the signal....

Do you have any clue why this happens? Should I initialize it somewhere in the main.c source code of the uart app to make it work?

I have a fair experience with nrf52 using the old SDK, but I am rather new to the nrf_connect and zephyr environment, so it is possible that I am missing something really basic....

Thanks in advance for your help!

Lorenzo

[JONATHAN LL]

What version of the nRF Connect SDK(NCS) are you using? there is a bug in 2.00 -2.2.99.
This PR should fix
https://github.com/nrfconnect/sdk-nrf/pull/10120/files#diff-9a498e7310940c0b624cfbe919175b9cd29b76a33bf89e703376229ec8ac5c24 


You could also share the two hex files with us and we can test to see if we get the same result on the same setup.


What version of the nrf52833DK and 21540EK are you using?

Regards,
Jonathan

[lbe]

Hello,

sorry for the late reply but I have been busy on other things.

Yes, I am in fact using NCS 2.2.0 (latest stable at the time of this writing), so I believe I am affected.

I tried to modify the indicated files following the PR you linked in my local installation, but I still get the exact same behaviour: lower RSSI with the -DSHIELD option than without it.

I am using a shield version 1.1.0 (2021.33) and a NRF52833 DK version 1.1.0, 2022.6

I am linking the two hex files as you requested; as I said I did not modify at all the example application bluetooth_peripheral_Uart, but I just tried to compile it for the 52833 + 21540 shield.

Thanks for your feedback, I hope we can figure this out.....

Best,

Lorenzo

zephyr_Shield.hex

zephyr_NoShield.hex

[Muhammad Usman]

Hi Jonathan LL  and Lorenzo, 

Thank you for the nice discussion. I have the same working environment and I followed all your instructions as it is. the only difference is that I am using nrf21540 DK.

In the second, case I also have the custom board which is nrf52833+nrf21540. 

I am facing the same issue. Can you please help me in this regard?

Thanks 

Muhammad Usman

[JONATHAN LL]

Hi Muhammad Usman , can you create a new ticket and reference this ticket and if you want you can name me and I will take the ticket. 

You can feed in additional info from the following questions:

Are you getting bad results with the nRF21540 DK? or is that your reference when testing with the nRF52833DK+nRF21540 Shield, and that is what performs bad?

Have you also tested with the RSSI Viewer app from nRF Connect for Desktop?

Are you using the latest version of NCS or version 2.2.0 as Lorenzo or something else?

Regards,
Jonathan

[Muhammad Usman]

Hi JONATHAN LL 

Thank you so much for the response and help! 

Yes, i already created the ticket, please find the link below for the ticket. I will further update this ticket if find more observations.

 nrf21540 working confirmation 

Thanks & Regards,

Muhammad Usman

[JONATHAN LL]

Thanks, will follow up on the other ticket for now. 

[Muhammad Usman]

Thanks, will wait for your response!