Bluetooth characteristics usage

RE: Bluetooth characteristics usage

Carles — Thu, 31 Jul 2014 10:43:53 GMT

You could do that, and then replace 4) and 5) in my suggestion with a notification with the value corresponding to the key being sent in a notification (or indication if you don't care about throughput and want the client to acknowledge) to the client. You could also combine both key and value in one single characteristic, since the ops are sequential, but I think it would be cleaner using 2 separate ones so that you can establish a max size and do different checks for each based on characteristic handle.

RE: Bluetooth characteristics usage

leo — Thu, 31 Jul 2014 10:36:53 GMT

Hi Carles, thanks! i was hoping you answer my question (saw your post about your new book) :) So you would use a second characteristic to communicate with the device, and not update and send a notification with the "char_get_value" characteristic? (To make it clear. You would separate the communication in 2 characteristics, 1 characteristic the smartphone can write, and 1 characteristic the smartphone can read?) Thanks a lot.. i think i will order the book now :)

RE: Bluetooth characteristics usage

Carles — Thu, 31 Jul 2014 10:18:34 GMT

Hi Leo,

There are many ways of accomplishing what you need using BLE, but it is not quite clear to me exactly which one would be best suited for you.

If your BLE device holds the data and the peer (smartphone for example) wants to use a key-value type storage, then you could simply:

Use the BLE device as a GATT server, the smartphone as a GATT client
Write Request from the smartphone to the BLE device to a characteristic you have set up. The Write Request contains the key.
The BLE device places the value in a second characteristic you have set up and acks by sending a Write Response
Read Request from the smartphone to the BLE device to the second characteristic you have set up.
Read Response with the value is sent by the BLE device

All write actions on the server are notified by means of a BLE_GATTS_EVT_WRITE event. If you want to be notified of read events too, you need to set rd_auth = 1 when populating your characteristic.

If you want to learn more about BLE basics, this book may be of help.