Using nRF9160 DK with nRF21540 EK

[Yun531]

Hello, just like the title indicated, I need help with setting up the nRF21540 EK with the nRF9160 DK.

For my application, since the nRF9160 DK has the nRF52840 on it, I wanted to use the nRF21540 EK as a shield to range extend the BLE signal coming out of the nRF52840. I also need to use the cellular feature on the nRF9160 DK for something else. The nRF9160 DK will be the main controller, of course. 

This is the closest post on the Q&A forum I can find. which set up the nRF21540 EK with the nRF5340 DK. I have an overlay file for the nRF9160 DK, which maps the GPIOs on the DK to the EK. However, I'm kind of lost after this step because I'm not sure what to do next, as from my understanding, the pins belong to the 9160 DK. Currently, my setup includes the EK as a shield to the DK, and the BLE SWF connector (J3) connects to the TRX SMA connector on the EK. Do I just need to program the 9160 and 52840, and the FEM will work? For example, I want to run the radio test sample to test the radio, would I just program the sample on the 52840, but then the nRF9160 DK is not one of the boards supported for this sample? 

I'm sorry my question seems basic, but I'm just a beginner starting out with Nordic. I've been looking at a few posts on the forum and the documentation as well, but I'm not sure where to start. Any guidance would be appreciated. Thank you so much.

[JONATHAN LL]

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

[Yun531]

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.