Creating a custom UART connection over BLE

RE: Creating a custom UART connection over BLE

endnode — Mon, 24 Jul 2017 19:01:13 GMT

BT protocols are vendor independent so in general there is no difference what chip is implementing it on "the other side". Actually it's pretty easy to develop device where you won't recognize what ship it is (without dissecting it physically). So without more details your question doesn't make much sense, all examples in Nordic SDK should work the same whatever devices is implementing the counter-part (remember that except some latest development all Bluetooth protocols are always peer-to-peer and BLE is always asymmetric so you need to have "matching pair" of devices to make it work).

RE: Creating a custom UART connection over BLE

tolab — Mon, 24 Jul 2017 16:53:35 GMT

Thanks! Do you also have any resources for someone looking to connect to a peripheral that is not a nordic chip, but instead any bluetooth device (i.e. A pair of bluetooth headphones)?

RE: Creating a custom UART connection over BLE

endnode — Mon, 24 Jul 2017 16:05:45 GMT

Cool, then spend some time by reading all the tutorials and then we can answer rest of your questions;) devzone.nordicsemi.com/.../ devzone.nordicsemi.com/.../ devzone.nordicsemi.com/.../

RE: Creating a custom UART connection over BLE

tolab — Mon, 24 Jul 2017 15:59:51 GMT

Sorry I am very new to this so I have many questions. What does it mean to provision a UUID?

Does this mean, if I change the given 128 bit UUID in the example to resemble the UUID of the characteristic I'm trying to read, it won't affect any of the other UUID's my board needs to read (i.e. the UUID for another service)? I am confused because they do not all have the same 128 bit form.

RE: Creating a custom UART connection over BLE

endnode — Mon, 24 Jul 2017 14:58:01 GMT

Not really. In Nordic BLE stack all UUIDs are 128-bit (that's actually true in BT SIG Core as well;). They just come in pair of values: 16-bit UUID + 128-bit UUID base. Now the only standard 128-base which is in SoftDevice pre-configured is the one defined for 16-bit BT SIG UUIDs (logical;). What Nordic BLE UART examples are doing is that they provision second (custom) 128-bit UUID to Soft Device during init and then they use it as base for all custom 16-bit UUIDs. This is the same on GATT Server as well as GATT Client side. SO the answer is: provision correctly your specific 128-bit UUID base and use it for provisioning all Service/Characteristic UUIDs together with 16-bit values (but I'm pretty sure this is already happening in Nordic SDK examples).

RE: Creating a custom UART connection over BLE

tolab — Mon, 24 Jul 2017 14:52:25 GMT

The original RX and TX characteristics are 16-bit UUIDs. The UUID for my custom device is 128 bits long. How do I adjust for this?

Thanks for the response!

RE: Creating a custom UART connection over BLE

endnode — Mon, 24 Jul 2017 14:49:42 GMT

If you change all UUID values correctly then GATT service discovery in ble_db_discovery module should make the job for you.