about maximum throughput of nrf51822

[Jones]

Hi,

I tried to use nrf51822 to update light intensity of 64 area to smartphone and then the smart phone will display those light intensity values in gray scale. I want make the data transmit as fast as it can. therefore I set the max connection interval to 10ms and min connection interval to 7.5ms. But the phone stop updates the data after a few second. I wonder is the bug from the ble or from the smart phone apps.

Also, I wonder how small the interval can be set.

[endnode]

Hi Jones,

Would be beneficial to get trace of radio communication (any BLE sniffer) to see what's happening and why connection breaks. Also note that while connection interval 7.5ms is great for throughput most of "mutli-applicational" centrals such as mobile phones don't like it. Normally both Android and iOS settle for connection intervals in the range of 40-50ms where they work OK (= are tested by mobile makers;).

Cheers Jan

[Jones]

Besides, I also want to know which flag I need to check to see when I can input a new packet data. I have tried a transmit finish flag, but the through put drop dramatically. It seems using this flag can't send data in each connection interval.

[endnode]

Wait are you GAP Peripheral or Central? And GATT server or client on top of that? Normally you simply push as many packets to the GATT layer of SoftDevice as possible (typically by using sd_ble_gatts_hvx or sd_ble_gattc_write function) - until you get BLE_ERROR_NO_TX_PACKETS error instead of NRF_SUCCESS. Then you simply wait for BLE_EVT_TX_COMPLETE event in your SoftDevice event handler and continue with the procedure (again until you are done or you get another BLE_ERROR_NO_TX_PACKETS). Packets are then utilized over connection intervals automatically by the SoftDevice and it of course depends on capabilities of both sides of a link. Again you can easily see all this if you plug BLE sniffer and read the trace.

[Stefan Birnir Sverrisson]

The answer on this thread could also be helpful

[Andrew]

For iOS minimum connection parameters see this document from Apple: https://developer.apple.com/hardwaredrivers/BluetoothDesignGuidelines.pdf

For Android 4.4 - 5.x the minimum interval is 7.5ms and for Android 6+ the minimum interval is 11.25ms

Some older Android phones don't do well at the minimum interval (Samsung Galaxy S3/S4, HTC M8, that era of phone) and you will want to do an interval closer to 30ms.

My guess for your specific problem is that you are requesting an invalid connection interval when you do your connection parameter update request and either the phone is dropping you or the connection update module sees that the parameters were refused and it is triggering a disconnect.