A BLE disconnection issue occurred randomly after the device had been functioning without any problems for many hours

[Tai]

Hi everyone,

We have devices using the BLE module (nRF52) deployed in clinics for testing. They have been functioning without issues until recently when we noticed occasional BLE disconnections. The following image shows data from one of the affected devices. Its RSSI value dropped significantly to -90 dBm, indicating weak BLE signal strength that could explain the disconnect. However, the device was positioned close to a tablet running the application connected to it, where the BLE signal strength should have remained strong. This inconsistency is what we find puzzling.

In another case, the RSSI value was within acceptable range (-68dBm), which couldn't lead to the BLE disconnection. 

We're thinking of if any issue with code optimization. Any suggestions to further investigate this issue would be greatly appreciated. Thanks!

[hmolesworth]

We had a similar issue with a disconnect due to RSSI when the sensor was supposed to be next to a tablet/gateway and it turned out to be a large body of water placed in close proximity to the tablet ie someone picked the tablet up and turned away from the sensor to better read the data and the human body blocked the 2.4GHz signal pretty well. 2nd case looks odd though unless a local microwave got switched on .. SDK or nRFConnect?

[Susheel Nuguru]

It is a bit hard for us to say anything with the signal characteristics of the traffic outside the SoC as the module makers normally have different packaging on top and different antenna options to use. Please try to ask the module makers on this first unless you can show us that this issue is from the nRF chip and not the packaging or external components issue from the module.

Try running your app on the DK and see if you see the same. If not, then it is mostly module issue.

[Tai]

Thanks for the reply, hmolesworth ! We're using the latest SDK 17.1.0.

Since deploying it in the clinics, people being around the device might be inevitable. Moreover, some other equipment that have interference might be introduced in the room as well. In this situation, it'd be great if you can suggest any solutions to protect the device from being disrupted by human body or other sources of interference! Thanks!

[Tai]

Thanks for your suggestion, Susheel Nuguru ! We'll ask the module maker and try to test with the DK. Will keep you posted.

Similar question asked hmolesworth above, any suggestions to prevent the BLE device from being disrupted by human body or other sources of interference? Any help would greatly appreciate!

[hmolesworth]

Maybe post the settings you have; these can be tweaked to reduce disconnection likelihood by delaying as long as possible a disconnect due to loss of signal. Other options are coded PHY or increased Tx power, but the issue may also be with the tablet. Changing orientation or raising height of either device or tablet or both can help, a lot depends on multipath signals so room size and wall coatings.