Samsung A series not detecting nRF52832

[loliplol]

Hi,

I'm currently developing custom board with nRF52832 and I'm experiencing weird issues.

It's mostly related to BLE, especially on Samsung A series devices (A3, A7, A50...). What we're experiencing is that these devices do not detect our custom nRF board.

I have tested it with multiple devices (S7, S8, S9, S10, Sony Experia, LG G6, DevKit, ESP32) and all these can connect to the board and see it while scanning.

Let's say we have A7 and S7 phones side by side and one of our custom modules between them. S7 will scan for available BLE devices, immediately detect it and keep seeing it (visible on RSSI graph). A7 on the other hand doesn't detect it, and if it does it stays there for a bit and then disappears. Important is that when A7 does detect it, RSSI is a normal value (like -25 or -30), which means that the signal strength. Speaking of signal strength, S7, S8, S9 detect it around 60-65m away and still has usable signal strength.

I haven't got a clue what is wrong. I tried flashing example apps (ble bleacon), still the same problem. I've tried flashing my custom DFU, while other devices detect it just fine, A series still doesn't work. Although, when I use the nRF onboard the Devkit, both A series and all other phones can see it.

Soft device used: S132 3.1.0

Thanks for any help!

[Carl Richard]

Hello, Loliplol!

The issue you describe have been commonplace for Samsung A series devices. Could you try the approach described in this thread?

Best regards,
Carl Richard

[loliplol]

Hi Carl,

We have found a bug in the PCB design.

I have to admit, this is a really interesting behaviour from Samsung A devices.

What we discovered:

- Cload capacitors on the 32MHz oscillator (supposed to be 18pF, originally it was 12pF)

When we discovered this mistake, we replaced the capacitors with a suitable value and all of a sudden all our devices showed up on Samsung A series devices.

Keep in mind, S7 S8 S9 S10 phones could see the module even before the change and keep to see it after the change. A series does not see it with old capacitors.

[Carl Richard]

Hi, Loliplol!

Great that you solved the issue, but I agree that this was an interesting behavior! My guess is that the other phones have more tolerance for timing variations that arise with wrong capacitor values.

Best regards,
Carl Richard