Mesh disconnection

[Allen96]

Hi everyone,

I recently finished developing a program that includes BLE, mesh and DFU.

Everything seems to be working but there is a problem with disconnection.

The real system includes 9 mesh devices which, for one reason or another, could disconnect due to the low signal quality.

I had already checked that, in the evaluation sheets, once the signal quality was restored, the reconnection was always verified.
With the PCB produced by us, however, this thing does not happen, and even with a good signal it does not return to connect to the network.
The code in both cases is clearly the same, the development uses a rigado module with external antenna. I checked the quality and disconnection by checking the RSSI in the porvisioner.

By removing the antenna, the device is no longer present and reconnecting it, in one case it reappears in the other instead it does not.

If anyone could help will be awesome. Thanks for the attention

AM

[Kenneth]

Sounds to me like some hardware issue, e.g. due to difference in hardware, maybe look for floating pins, undefined pins, difference lfclk source, supply voltage, poor grounding, electrical?

Is there no asserts or does it seem as the application is stuck somewhere in code execution?

Kenneth

[Allen96]

Hi,

Sorry for the late reply.

The connections that we have done are the following:

- pin number 22 and 24 are used for the USART communication with an STM32

- pin number 43, 44 and 39 are used for the programming

No other pin are used. The module used is the BMD300, without any crystal (I've changed a portion of code about clock settings). We have used only 0.1uF capacitor for decoupling but should be good since the 4.7uF capacitor is included.

If you want i can post the portion of the code where I changed the clock configuration and the pcb design as well.

Thank you for the help.

AM

[Kenneth]

Have you checked that you have followed chp 11. RF Design Notes: 
https://www.mouser.com/datasheet/2/883/BMD-300-Series-DS-V1.11-1147364.pdf

[Allen96]

Hi,

thank you for the information. We are using the module that use an external antenna, the area under the connector is free from copper anyways, the ground plane is not as indicated. 

I've read that the changes in ground plane size can effect the power of the transmission, isn't that irrelevant since the signal is received clear before i take the antenna out?

Thanks for your time

AM

[Kenneth]

Changes in (or more specific poor) grounding can lead to the design more prone to noise, for instance from serial interface, this can influence both transmissions, but also reception. So you may want to disable serial interfaces during testing to check if that may be the case.

Best regards,
Kenneth

[Allen96]

Sorry for the late reply,

We got the opportunity to change part of the ground plane and make it more similar to the referenced one.

The result is perfect, the device will automatically reconnect as supposed to be.

Thanks for your help

AM