Third peripheral sending Empty PDUs, dropping packets

RE: Third peripheral sending Empty PDUs, dropping packets

Hung Bui — Wed, 20 Dec 2017 12:59:32 GMT

BLE is a reliable protocol, meaning there will be no packet missing on link layer. A packet will be resend until it's acked. It could be the central application code cause the packet notification packet not processed, but we don't have control over it.

As you can see in the Test 3 E5 trace, there was no notification packet, I don't know how you can receive data (if not from read request).

RE: Third peripheral sending Empty PDUs, dropping packets

mwmccabe — Tue, 19 Dec 2017 18:46:01 GMT

In our protocol, a "data frame" is composed of five notifications. This data frame has a frame counter which is used to determine whether or not frames are dropped. By losing I just meant dropped/never received by our software (so presumably the central as well.)

RE: Third peripheral sending Empty PDUs, dropping packets

Hung Bui — Tue, 19 Dec 2017 17:10:59 GMT

How do you send data from E5 to central ? How do you check if it's "losing" ? what exactly is losing ?

RE: Third peripheral sending Empty PDUs, dropping packets

mwmccabe — Tue, 19 Dec 2017 14:04:02 GMT

My central is still receiving data from sensor E5 in Test 3, but losing roughly 50% of it. How can this be if there was no write request?

RE: Third peripheral sending Empty PDUs, dropping packets

Hung Bui — Tue, 19 Dec 2017 11:45:11 GMT

Hi mwmccabe,

I see no problem with Test3 Sensor E5, the connection was terminated properly. Empty PDU just mean the central didn't do anything and then disconnect. I don't see the central does any write request to enable notification.

Test 2 Sensor E5, I don't see any connection, can say nothing here.

Test 1 Sensor D0, in this trace actually we can see something not normal. The central stopped sending empty PDU or at least the sniffer couldn't capture any packet from central.

LL_CHANNEL_MAP_REQ shouldn't be an issue here, the connection is fine until very long after the new channel map took effect.

From those data you provided, I don't see any issue from our side. Would suggest you to test with other centrals, suggest to test with central from other brand.

I assume you created an app that can handle multiple peripherals.