Using nRF9160 DK with nRF21540 EK

RE: Using nRF9160 DK with nRF21540 EK

JONATHAN LL — Tue, 29 Apr 2025 08:14:35 GMT

[quote user="Yun531"]I found out that leaving the FEM on all the time was a bad idea as it could introduce unwanted noises and degrade the FEM overtime. [/quote]

Yes, the FEM is noisy so having it on all the time is not recommended, it also draws a lot of current so it power is of concern then I would not recommend that it is on all the time as well.

Happy to help, if you have more questions ask here or create a new ticket if the topic is different and we will do our best to help you.

Regards,
Jonathan

RE: Using nRF9160 DK with nRF21540 EK

Yun531 — Sun, 27 Apr 2025 03:34:26 GMT

Hi Jonathan,

After reading more in the user guide and the documentation, I found out that leaving the FEM on all the time was a bad idea as it could introduce unwanted noises and degrade the FEM overtime. I'll follow your original suggestion of using the nRF21540 DK instead.

I appreciate your time to answer my question in detail. Thank you so much.

RE: Using nRF9160 DK with nRF21540 EK

Yun531 — Fri, 25 Apr 2025 20:17:11 GMT

Hi Jonathan,

Thank you for your reply. I'm currently using the nRF21540DK and connecting it to the nRF9160DK just as you suggested. However, I was thinking that it introduces a redundant component since both of them have the nRF52840 SOC on them. If there is no other way, I'll continue with this setup. But I'd like to ask you a few questions regarding the nRF21540 EK:

1. For my application, I'll put this "set up" at some remote location, and use cellular connection as a simple way just to control the BLE settings. For example, use nRF Cloud and send commands to change the frequency, change the antenna, enable/disable the FEM. In this case, is it necessary for the nRF52840 to access the pins on the nRF21540 EK? My confusion comes from the timing issue part, can I just enable the FEM before a transmission and disabled it afterwards? My application only do TX and not RX.

2. From the nRF9160 DK Document, I notice the table about the board control pins. Link here. I'm a little confused about this, does this mean that the 52840 controls what is connected to the 9160 DK pins? Or does it show what pins on the 52840 connect to what pin on the 9160 DK? When you said:

The pin out on the nRF9160 DK for the pin headers are connected to the nRF9160, so you don't have that many pins available for the nRF52.

Does that mean that a few pins on the 9160 DK are available for the nRF52? Could you point me to the right place in the documentation? I'm having a hard time finding that info besides the Board Controller section.

RE: Using nRF9160 DK with nRF21540 EK

JONATHAN LL — Fri, 25 Apr 2025 09:10:11 GMT

The pin out on the nRF9160 DK for the pin headers are connected to the nRF9160, so you dont have that many pins available for the nRF52, so it will not work as a shield for the nRF52840. So controlling the nRF21540 through the nRF9160 is not a good idea as there might be issues with timing. I am unsure how to best handle this as you might have to handle this in SW on the nRF52 side and then adjust for the timing delay that would happen with forwarding the control to the FEM. We currently dont have a example on how to do this.

So it does not work the way you want probably and if you plan to make a custom PCB at any point then this would not be the way to do it.

I would recommend that you use an nRF21540DK and connect it to the nRF9160DK, this way you will get the best performance and can still use the nRF9160 as the main controller.

Regards,
Jonathan