ATT delay on BLE notification

RE: ATT delay on BLE notification

wichmann — Wed, 11 Sep 2024 11:48:46 GMT

Thanks for the response. This happens on multiple Android devices, at least one of which was high end at the time, and with multiple Android versions (8 and 10). Other devices from the same manufacturer and similar release date do not have these problems.

I did some more testing and I'm now pretty sure that my explanation was right. Reducing the connection interval also reduces the delays. I just can't understand why the hardware or software stack would limit the number of packets this severely. But I guess you're right. The number probably can't be configured. I did find the Android method requestConnectionPriority(), but this seems to just reduce the connection interval. The number of packets seems to stay the same. This just leaves me with reducing the connection interval on all plattforms. Still thanks for the help.

RE: ATT delay on BLE notification

Simonr — Wed, 11 Sep 2024 11:23:41 GMT

[quote user=""]

every fourth or fifth ATT packet is delayed by about 30 ms.

[/quote]

Does this only happen on these select two phone models or do you see it on other devices as well. This sounds very much like a problem with the Android stack on the device you're using and there are a lot of BLE related issues especially in older Android devices. I can't say I have seen this issue specifically before. I would assume this is only an issue on older low-end Android devices.

For reference I think your explanation makes sense, but I'm not aware of a way to increase the number of packets an Android device can receive per conn. interval. I would guess it's set in the stack and not configurable though.

Best regards,

Simon

RE: ATT delay on BLE notification

wichmann — Tue, 10 Sep 2024 12:53:06 GMT

Just after posting, I think I found a possible explanation. This might just be the limit of number of packets per connection interval. It's just that one phone allows at least 50 or so packets per interval, while the "problem" phone only allows four or five. After these packets are sent, a pause is inserted until the next interval starts (about 30 ms at 37.5 ms connection interval).

That would mean, that my only possible option would be to lower the connection interval. Or are there any options on Android side to increase the number of packets or at least detect how many packets are allowed?