Android Master Control Panel not updating characteristic value

[Bret Foreman]

I've got a test app on my nRF51 DK that calls sd_ble_gatts_hvx as fast as possible to test maximum data rate for the Notify of a characteristic. This all works great. The maximum data rate with a 20 byte payload is 13.33Kbytes/sec when measured against a 10 second timer. Impressive.

I'm putting the data rate (divided by 100) into one of the bytes of the characteristic so that I can conveniently see it by connecting with my Android phone and using the Master Control Panel (MCP).

The problem is that MCP is not updating the characteristic value reliably. Sometimes the byte value that I'm sending comes through but most often not. I can see with printfs in my code that all is well on that side and sometimes MCP works too, but not often. Is this a known issue? Is there a workaround?

[Aleksander Nowakowski]

Hi,

The nRF MCP app refreshes the services list every 400ms or so, as far as I remember. Otherwise the GUI was completly not responsive. Even now, with this feature it gets very slow if you send data very fast. The reason is the Log (log refreshes every time a value is received).

If your value was not shown on the services list you can check the log. You should find it there. I think none of values sent should be missed and the log should contain all. If you want to measure the speed the nRF MCP app is not quite (yet!) good way to do so, as the UI is very slow. It would be a much better idea to write a very simple app, with no/almost no UI that just writes the data to the logcat.

Best Regards, Aleksander

[Bret Foreman]

Where does nRF Logger store the log files on the phone? I've got my phone mounted as a media device on my laptop and I'm browsing the folders but I can't find where those files live. I want to download the logs so I can parse out the data for analysis.

[Bret Foreman]

Upon further reading, it looks like the logs are in a database, not a text file. Is there away to export them to something like a CSV so I can process the data elsewhere?

[Aleksander Nowakowski]

Yes, the logs are kept in the database. You may export log sessions to text files, eigher from log details (menu->save)or by selecting multiple log sessions on the list (long click the first session to select, than click other, menu->save). I hope it's enough.

[Bret Foreman]

I did some more experiments and the log is simply not written as fast as the notify events. So it gets about 2 minutes behind for every 1 minute that it runs. This makes it challenging to use the logger to see anything real-time in this test. Looks like I'll have to write my own app...

[Aleksander Nowakowski]

I agree. A simple app that puts logs to logcat would be much faster. Although I'm planning to add bandwith measurement feature to MCP one day.