Argon BLE Signal Issues

Hi,

I have been using Argons for over two years now and have come across a problem I cannot seem to find an answer to. I have made a PCB that uses the Argon to control some equipment that goes on vehicles in the winter. The equipment is controlled via BLE and a smartphone app. There have been some units recently where the operator is losing BLE connection when they bring their smart phone into the cab of the truck. Every PCB is tested before it goes out for signal strength, most seem to be working in the field. I am seeing units work perfectly for days/weeks then the operator starts having disconnections when getting back into the cab of the truck.

I received my first board back today to look at and it seems that the Bluetooth signal is greatly reduced from what it should be. I tried some different antenna configurations and on a new PCB and this returned PCB that is having signal issues. The BLE tx level is set to 8. Here are the results:

Internal Antenna chosen in Firmware
New board - 68 dBm
Issue board - 80 dBm

External Antenna chosen in Firmware, using supplied Particle Antenna
New board - 60 dBm
Issue board - 80 dBm

External Antenna chosen in Firmware, using our 6dBi gain Antenna
New board - 54 dBm
Issue board - 83 dBm

External Antenna chosen in Firmware, no antenna hooked up to the U.Fl connection
New board - 92 dBm
Issue board - 82 dBm

The test was conducted indoors and the reading was taken about 30 feet from the boards. It seems that the antenna selection in the firmware and using different external antennas does not change the signal strength on the board with issues.

Has anyone seen anything similar happen to an Argon? Everything else seems to work fine and the unit still works as it should if you stand next to it, just the BLE signal strength is affected. The PCB is powered by 12v and reduced to 5v going into the Argon.

Any thoughts are appreciated.

Hi, and welcome to the community!
I never faced such an issue, but here’s what I have in mind:

  • Could it be that there is something in that cabin that is impacting the signal?
  • Could it be that the battery of that particular truck is very noisy?
  • Could it be that the cabin in those impacting trucks is better caged, insulated, whatever?

I could not distill from your post that the unit that you got back seems to be faulty, that is why I’m contemplating other sources of trouble. Feel free to ignore if you ruled them out already.
Thanks!
Gustavo.

Hi Gustavo, thanks for the reply.

I was able to inspect the unit while it was on the truck it was operating on. The operator had the same tablet with that he was using to operate the unit in the field. We were not able to replicate losing the connection in the cab. So I used the Bluefruit Connect app to check the signal strength of the Argon and found that it was very low, even when standing by the Argon.

I ended up putting a new control box on his unit and measured the signal strength in the cab of the truck. With the new control box I was reading about -62 dBm compared to the -90 dBm that his current box was putting out to the cab.

So the numbers for the tests above are from a stable power supply on my bench, in which the Argon seems to have substantially diminished BLE signal strength.

I am trying to find what the units having this problem have in common but so far have had no luck. I checked the power supply to the Argon while the user had his truck running and it was reading a steady 5v. What is unusual is nothing else on the PCB seems affected and everything works as normal.

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what if you re flash firmware that will set again the BLE tx level to 8?
would the readings go up?

Not that I have seen.

I flashed the Argon with Tinker to reset it to a default state. Then flashed the Argon with my user firmware again to see if that changed anything, it did not seem to affect the signal strength at all. I have the following in the Setup of my firmware:

BLE.selectAntenna(BleAntennaType::EXTERNAL);
BLE.setTxPower(8);

I did try to reduce the power level to 0 and that did make the signal worse. I was reading about a -90 dBm about 3 feet away from the Argon.

wow, this one is puzzling!