bluetooth advertising cannot be seen on other devices

[joposter]

Hi,

So we are currently debugging our custom nrf52832 board. It is equipped with both a 32.768khz and 32Mhz Oscillator, which both SEEM to work.

I tested both using the tips found around the forum, for the HFCLK using this loop

NRF_CLOCK->TASKS_HFCLKSTART = 1;
while (NRF_CLOCK->EVENTS_HFCLKSTARTED == 0) {}

and for the LFCLK using the softdevice's own lock loop (we had a case when the LFCLK was unable to start, which made the softdevice lock up. Since this is not happening anymore i ASSUME the LFCLK to be working).

GPIO's work and RTT Logging is working as well. Now we tried to add bluetooth advertising, which works on the development kit (pca10040) but not on our custom board, although there are no errors coming up on the log output.

I also tried the ble_app_uart example with the the devkit as the bluetooth central, and saw a bunch of disconnects with reason 0x3E.

<info> app: Connecting to target 0E42FAB76FE6
<info> app: Disconnected.
<info> app: Disconnected. conn_handle: 0x0, reason: 0x3E

I suspect our RF routing to be the problem. This is our layout, and i cannot really see a problem.


I am at my wits end and would appreciate any kind of input here.

with kind regards

Julian Daube

[haakonsh]

If this is a 2-layer board, then you're missing the return path for the antenna. Without a proper return path, the antenna won't oscillate properly. 

The bottom ground plane needs a clear path from the antenna into the radio's GND pin. See our reference design for comparison. 

The placement of the nRF52's LC filter is also not ideal, the same is true for the alternative antenna connector. There will be some power losses.

I suggest you open a private case where you request an HW review of your design files.