uart receiving date delay on Android 5+ using 51822

RE: uart receiving date delay on Android 5+ using 51822

endnode — Sun, 26 Mar 2017 07:32:15 GMT

I'm afraid your expectations simply don't meet reality;) You can try to force the other part of link to lower connection interval to 20ms or below but there will probably be devices which will simply not follow...

RE: uart receiving date delay on Android 5+ using 51822

eric — Sun, 26 Mar 2017 03:26:20 GMT

Thanks,endnode.

we want to measure electricle current change on human body .So we designed the devices to send data in real time ,that's why we want to send data as high rate as we need. the devices will send data(1 bytes) to phone each 20ms(=50Hz).

Some phone is oK ,no matter Andrioid 4.3 or 5+, some phone has serious dalay, for example ,Huawei Mate8 is ok ,but Huawei Mate9 can not .

RE: uart receiving date delay on Android 5+ using 51822

eric — Sun, 26 Mar 2017 03:16:15 GMT

thanks for your advice. we wil try this API and see what happen.

RE: uart receiving date delay on Android 5+ using 51822

Turbo J — Sat, 25 Mar 2017 20:35:56 GMT

Android 5.0+ also has an API for adjusting connection interval:BluetoothGatt.requestConnectionPriority()

RE: uart receiving date delay on Android 5+ using 51822

endnode — Sat, 25 Mar 2017 10:14:26 GMT

Hi, what GAP roles (Peripheral/Central) are you having on each side of the link? What connection interval is used? In case it's more then 20ms (= 50Hz) do you negotiate faster? Do you have RF trace of what is happening in the air? Several early Kit Kat Android phones were able to go as low as 7.5ms connection interval while most of Android devices since 5.0 are using 48.5ms (when in GAP Central role). This would easily explain why your 50Hz expectations are too ambitious. The same for iOS: it uses connection interval 30ms when it is GAP Central so again normally you won't achieve 50Hz.

I'm wondering what do you actually mean by 50Hz. If your samples are short (few bytes) then you can simply stamp them and stream over the PDUs independently on the connection interval. Until you achieve better throughput then 50x(sample size) then you can easily restore the data in the mobile without any loss of information. Sure, there will be always delay up to 1 connection interval (30~50ms).

Cheers