nRF52840 Dongle (PCA10059) - BLE Central UART / USB CDC ACM - Bluetooth Range is Very Limited?

[AdamWilsonCPI]

Hi,

I'm working on a project where we are receiving sensor data from a BLE peripheral (BL654), and publishing it to a piece of PC software via UART/FTDI cable from a BLE central (nRF52840 Dongle PCA10059).

The next logic development step is to implement a virtual USB COM port using the nRF Dongle itself, so we can do away with the FDTI breakout and enclosure.

I've successfully implemented the USB CDC ACM example alongside the BLE UART in my code project, using SDK v15.3.0 and based off the integrated example available in SDK v15.3.0. The COM port itself works fine and I can see valid data over TeraTerm, however the BLE range is extremely limited (< 10cm). Using exactly the same hardware (plus the FTDI cable), and replacing the COM port code with the previous UART code, the range is very good (> 10m).

Is there a bug in the SDK (v15.3.0) or SoftDevice (S140 v6.1.1) that could reduce BLE Tx power when USB CDC ACM is used? Do you have any other suggestions?

I'd be happy to share the project privately if necessary.

Many thanks,

Adam

[AdamWilsonCPI]

Hi Edvin,

Thanks for getting back to me :) 

I understand what you mean, thank you. BLE read events should only be occurring every 200ms with only 100 bytes of data, so it shouldn't be too taxing for the system - however, I believe that missing events is the problem, but this was not the cause.

I went over the differences between my project and "usbd_ble_uart" (I couldn't use this one directly, as this is for a peripheral and not a central) with a fine-toothed comb, and found a call to "nrf_cli_process()" in the idle state function which must have been left over following integration. I've removed the call, and both the BLE and USBD seem to be working fine now!

I'll continue testing and let you know if anything changes. Thanks for all your help!

Many thanks,

Adam

[Pingvin]

Can I get the source code?