Does BLE take Notification in order?

FrankXu

Hi,

Q1: When I use notification to transfer a queue of data, will the master receive all the packets in the same order I send from the slave, or the order of the packets may mixed?

I've looked at the old posts.

In : e2e.ti.com/.../374508 , TI says 'Yes'.

But in: http://e2e.ti.com/support/wireless_connectivity/f/538/p/183129/674531#674531, TI says 'No'

So, I'm confused.

Does the BLE stack have some mechanism to keep the notifications in order?

Q2: I call GATT_notificaion to notify the data. And if GATT_notificaion returns UNSUCCESS, I will recall the function with the same data in the next period event.

Does BLE stack have some mechanism to make sure every notification packet is transmitted and no packet is lost?

Thank you.

Frank

over 10 years ago

0 CM2015 over 10 years ago

Expert 1060 points

I believe they should be in order, note that the link layer maintains successful transmission using acks, so there might be packet re-transmissions but I think it must finish receiving the retransmitted packet prior to allowing any other packets so they should remain in order and should be reliably transmitted. Packets should not be lost/missed unless there is strong over the air interference/low signal rate, in which case the link layer will repeatedly try to retransmit and would fail eventually and I'm guessing would disconnect the peripheral.

0 FrankXu over 10 years ago in reply to CM2015

Genius 3500 points

Hi CM2015,

Thank you very much.

I think it's very probabliy as what you said. It's just that the two posts confused me. Waiting for TI's official answer.

Best regards.

Frank

0 Tim C over 10 years ago in reply to FrankXu

TI__Mastermind 34660 points

Hello. Both of your links go to the same post. In any case, yes all notifications will be transferred in order.

You do need to ensure you are correctly handling flow control with the controller. That is, you need to check the return value of GATT_Notification to check for success (0x00). If you do not receive success, you will need to attempt the GATT_Notification again. See the "High Throughput Example" from the wiki page for more information: http://processors.wiki.ti.com/index.php/Category:BluetoothLE.

0 FrankXu over 10 years ago in reply to Tim C

Genius 3500 points

Hi Tim C,

Sorry, I put the wrong link.
In: e2e.ti.com/.../674531, it says 'There is no guarantee.'.
" which obviously was proven to not be reliable."
Frank

0 Tim C over 10 years ago in reply to FrankXu

TI__Mastermind 34660 points

Hello Frank. That thread is from 2012 and relates to an old bug. This has since been fixed and you will never see out-of-order or missed packets.

0 FrankXu over 10 years ago in reply to Tim C

Genius 3500 points

Hi Tim C,

Thank you very much!

Frank

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Does BLE take Notification in order?