sending data over ble

RE: sending data over ble

Bill Siever — Wed, 21 Oct 2015 13:31:36 GMT

No. The Bluetooth Specs define the packet structure. 2) No. Again, packet size limitations (and notifications appear to be a single packet). Again, you can send multiple notification (or indication) packets. If using this approach, you may be best to use indications since they will confirm receipt. (Also, it looks like you posted further questions as answers. It would have probably fit better as a comment. Perhaps a forum moderator can adjust this thread)

RE: sending data over ble

sowmya — Wed, 21 Oct 2015 11:22:26 GMT

Hello ,

Is it possible to send more than 20 bytes in single packet?
Is it not possible to send larger data(more than 20 bytes) in notification characteristic?

Regards, Sowmya

RE: sending data over ble

sowmya — Wed, 21 Oct 2015 05:30:48 GMT

Hello Bill, thank you for the information. I made an approach to send data with more than 20 bytes by splitting the long data into 20 bytes each and it is working. For long write I need to use user memory space and I am working on that and get back to you.

RE: sending data over ble

Bill Siever — Tue, 20 Oct 2015 23:42:20 GMT

I believe the notify/indicate messages are actually limited by the BLE specs. A few options: a) send multiple notifications/indications (possible with sequence numbers and offsets in addition to the data) or b) Just use the notification to trigger a read from the central (the notification doesn't contain data; the read could be a long-read of more than 20 bytes. This seems to be the approach recommended in version 4.1 of the Bluetooth specs).

RE: sending data over ble

sowmya — Tue, 20 Oct 2015 13:38:29 GMT

Yes I searched in forum and I am able to send more than 20 bytes. Now I need to go for long write. I will open one more thread regarding long write. Thank you all.

RE: sending data over ble

MartinBL — Tue, 20 Oct 2015 11:22:21 GMT

There are several threads regarding this here on devzone, e.g. this and this.

RE: sending data over ble

sowmya — Tue, 20 Oct 2015 08:17:11 GMT

Hi, one more question is, how to send more than 20 bytes of data? I changed the variable length and also maximum length in GATTS structure but it is not working. Can anyone guide me?

RE: sending data over ble

sowmya — Mon, 19 Oct 2015 13:19:09 GMT

I configured the CCCD to receive characteristic and it is working. I had used MCP to enable notification.

RE: sending data over ble

Bill Siever — Mon, 19 Oct 2015 13:12:34 GMT

If the characteristic is properly configured as readable, then you can poll for the data (read it).

If you want push-style data updates (an update is sent every time there's new data), the characteristic will need to support either indications or notifications as well as have a client characteristic configuration descriptor (CCCD) to allow the client to opt-in to receive the updates. I'm guessing that you haven't used the MCP to enable the notifications/indications on the characteristic.

See the other posts on the CCCD, indications or notifications. There are also several examples in the SDK.