Detecting an External antenna

[viet.nguyen]

Hello all,

Ive combed through the NRF52840 datasheet and the BMD341 datasheet, and SDK examples attempting to determine if through software (and possible hardware change) if its possible to detect if an external antenna connected through a UFL connector is connected and working or not.

Currently I only find mentions of the NFC antenna, not the external antenna.

An ideal solution may sound like:
1. You can read this internal register to determine if the antenna is working or not.
2. You can measure this pin to determine if the antenna is connected or not.

Thanks for any input on this topic.

[JONATHAN LL]

Hi,


The BMD341 module is based of the nRF52840 SoC, and there is no built in solution to figure out if there is a antenna connected or not. 

So there might be a solution with external HW, so some circuitry that could detect if something was connected to the UFL connector, but not aware of a simple solution here. 

For what purpose is this? 

There are switches like the SWF or similar in the family that can be used for something like this but they are primarily used for testing and verification. You can see examples of this on our Development Kits. Liker its shown here in the RF measurements section https://infocenter.nordicsemi.com/topic/ug_nrf52840_dk/UG/dk/hw_rf_measure.html?cp=4_0_4_9 if you where to connect something to J1 connector it would automatically switch. 

And just to clarify there are no internal antennas on the module. 

Regards,
Jonathan

[viet.nguyen]

Hi Jonathan,

The purpose was to detect if the antenna was connected, so the system itself would be able to detect if it can successfully broadcast. If there is no simple solution that is alright. I was just wondering if I was missing anything.

Aside from complex circuitry and observing any nordic library errors. How would one internally detect if bluetooth advertisements from the device are being sent?

Thanks for getting back to me,
Viet

[JONATHAN LL]

The device will "send" the signal out on the ANT pin regardless if there is a antenna there or not. And there is no feedback "internally" if the signal has been successfully transmitted over the air or not. 

What could be done is to try and do a scan, if nothing is detected then one could assume that there is not antenna connected. This will off course not always be true as in some cases if the device is either in a faraday cage or some where where there are no BLE activity the result would be similar even tough a antenna would be in place. 

So there is know way of knowing if a advertising has successfully been sendt over the air unless some external device is involved. You could use a sniffer, a different device to scan for example. 

Regards,
Jonathan