nRF Connect App: slow BLE Rx data logging

RE: nRF Connect App: slow BLE Rx data logging

Aleksander Nowakowski — Mon, 10 May 2021 15:06:04 GMT

What's the connection interval? Minimum supported by Android is 11.25ms and 7.5ms for service discovery only.

RE: nRF Connect App: slow BLE Rx data logging

StevenW807 — Tue, 04 May 2021 00:15:35 GMT

Thanks, Aleksander Nowakowski! I fixed the problem by modifying the following code:

/**< The advertising interval (in units of 0.625 ms. This value corresponds to 40 ms). */
#define APP_ADV_INTERVAL 50

...

/**< SAADC sample rate in ms. */ 
#define SAADC_SAMPLES_IN_BUFFER 1
#define SAADC_SAMPLE_RATE       30

For other users, please note that according to BLE 4.0 specification, General connectable and scannable advertisement packets' time period ranges from 20 ms to 10.24s in steps of 0.625ms (reference link). Therefore, APP_ADV_INTERVAL ranges from 20ms (value = 32) to 10.24sec (value = 16384).

Also, when we set APP_ADV_INTERVAL value, we need to consider SAADC_SAMPLE_RATE. It's because in my project, the BLE device sends the string to the BLE central device by calling the saadc_callback() function. So APP_ADV_INTERVAL (in ms) must be > SAADC_SAMPLE_RATE (in ms).

Please let me know I understand them correctly or not. Hope this could help other people, too.

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My follow-up question:

My SAADC t_ACQ + t_conv = 3us + 2us = 5us. Then, I set SAADC_SAMPLE_RATE=5ms. I would like to achieve max BLE broadcasting rate as possible. So I set APP_ADV_INTERVAL=20ms (value = 20/0.625=32). But the BLE connection on nRF Connect App only works for a few seconds. Then, the App told me: Error 8 (0x8): GATT CONN TIMEOUT.

If I set APP_ADV_INTERVAL=31.625ms (value=50), SAADC_SAMPLE_RATE=30ms, then, no problem.

Do you know why, please?

RE: nRF Connect App: slow BLE Rx data logging

Aleksander Nowakowski — Tue, 13 Apr 2021 17:13:25 GMT

Hello,

Do you have nRF Logger app installed? You can try it with that app installed. But i don't think there will be a difference.

I thought that all events are logged, just that they're displayed every second. The list of services also should be refreshed each second, otherwise the app becomes unusable if data is coming to fast.

You may also try nRF Toolbox app, where there's no any buffering, so it should log all events. With nRF Logger installed it will also be saved there so you can export them to a file.