Advertisements forever affect.

[mrezan]

Hi,

I've made custom boards using nrf52840. 
In my application I did advertise forever with interval of 200ms.

Now after several weeks of tests I've two boards out of seven that can't see the advertisement.
I tried debugging but it had no problem when doing the advertisement.

Then I thought the components around the PCB antenna were damaged.
So I tried to change it one by one but it was still the same.

I find out without the components around the antenna (mean ant pin not connected to PCB antenna).
The good board still can see the advertisement. The defect board still can't see it.

Now I suspect the MCU is the problem one. I have not changed it yet.

Is an advertisement forever not suitable using nrf52840?
Any suggestion to handle the advertisement forever that does not affect MCU to easily damage?

Thanks & Best Regards,
Rezan

[Kenneth]

There is no known problem that should prevent infinite advertisment to not work. Did you check if re-programming the chips made them work? Is the power supply stable? I think the chip or surrounding components (e.g. crystal) may have been damaged somehow if it worked previously.

Kenneth

[mrezan]

I reprogrammed it. Still the same. I did it many times.
The Power supply is stable. I've tried different sources but it is still the same.
A good one has no effect when changing power.
The other function of the chip is good. Communicating to sensors using I2C, SPI and UART is ok.
Only BLE problem.

Best Regards,
Rezan

[Kenneth]

If it's only affect BLE, then it is likely related to the external 32MHz crystal circuitry in some way. I would start by replacing crystal and/or check it mounted correct etc.

Kenneth