Toit
#Bluetooth GATT Handle to UUID Mapping
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z3ugma 04/21/2024 05:48 PM
At https://libs.toit.io/ble/class-RemoteCharacteristic the docs describe a BLE GATT characteristic and let you access the UUID of the characteristic.
Separately is the concept of a BLE
Does Toit keep a mapping of the
Separately is the concept of a BLE
handleDoes Toit keep a mapping of the
handleuuid
floitsch 04/21/2024 05:51 PM
I recently worked on the BLE library again but I didn't see any reference to the term "handle". My first instinct is that the handle is not exposed. I would need to look at the code to know more.
floitsch 04/21/2024 05:51 PM
The BLE code is based on nimble. So maybe you can find more information there.
z3ugma 04/21/2024 05:54 PM
Check out something like https://stackoverflow.com/questions/75428882/trying-to-understand-ble-uuids-and-handles-with-bluetoothctl-example
when first interrogating a BLE device, a mapping of the handle to the UUID is maintained.
When you sent the actual BLE packet, it references the handle and not the UUID
when first interrogating a BLE device, a mapping of the handle to the UUID is maintained.
When you sent the actual BLE packet, it references the handle and not the UUID
z3ugma 04/21/2024 05:55 PM
nimBLE has
RemoteCharacteristic::getHandle().z3ugma 04/21/2024 05:56 PM
which is similar to the
how you get the UUID?
NimBLEUUID NimBLERemoteDescriptor::getUUID ( )how you get the UUID?
floitsch 04/21/2024 05:56 PM
The uuid is part of the characteristic. No?
floitsch 04/21/2024 05:56 PM
That's how it is referenced.
z3ugma 04/21/2024 05:57 PM
the characteristic has 2 properties: a uuid and a handle
z3ugma 04/21/2024 05:58 PM
RemoteCharacteristic::getHandle()
RemoteCharacteristic::getUUID()
^^ 2 different attributes that nimBLE lets you fetch with regard to a given characteristic
RemoteCharacteristic::getUUID()
^^ 2 different attributes that nimBLE lets you fetch with regard to a given characteristic
floitsch 04/21/2024 06:00 PM
I intend to work on the BLE library tomorrow. I will read up on handles then.
z3ugma 04/21/2024 06:23 PM
cool!
During the initial connection when you discover the services and characteristic, the BLE packet that is sent is called
use the BLE opcode : Read By Type Request (0x08)
which matches up the Handle to the UUID
During the initial connection when you discover the services and characteristic, the BLE packet that is sent is called
use the BLE opcode : Read By Type Request (0x08)
which matches up the Handle to the UUID
floitsch 04/21/2024 06:34 PM
I'm not yet familiar with the handles, but what does that mean for Toit?
Do we do it right or wrong? Is something still missing.
Do we do it right or wrong? Is something still missing.
z3ugma 04/22/2024 02:28 PM
yes - right now, I need to send a write command to a characteristic GATT UUID.
If I know the handle but not the UUID, then it's a bunch more debugging to figure out which handle matches up to which UUID
if I know the handle, it would be nice to directly be able to identify a characteristic by its handle instead of by its UUID
If I know the handle but not the UUID, then it's a bunch more debugging to figure out which handle matches up to which UUID
if I know the handle, it would be nice to directly be able to identify a characteristic by its handle instead of by its UUID
z3ugma 04/22/2024 02:30 PM
While we are at it:
BLE's L2CAP protocol allows a packet to say if it expects more data
BLE's L2CAP protocol allows a packet to say if it expects more data
z3ugma 04/22/2024 02:30 PM
that would also be really nice to implement when subscribing to a GATT, to know if we need to await an additional packet
floitsch 04/22/2024 02:54 PM
Ok.
floitsch 04/22/2024 02:55 PM
1
I have been working on the BLE library the whole day, and will probably continue to do so tomorrow as well.
I will see if I can expose the handle and the 'more data' flag. (assuming that's what it is).
I will see if I can expose the handle and the 'more data' flag. (assuming that's what it is).
1floitsch 04/23/2024 05:07 PM
1
I have uploaded a PR for the handles, but I couldn't find any information on how to get to the "More Data" header field.
If you know how to get to it in nimBLE/ESP-IDF I can have another look.
If you know how to get to it in nimBLE/ESP-IDF I can have another look.
1
floitschI have uploaded a PR for the handles, but I couldn't find any information on how to get to the "More Data" header field. If you know how to get to it in nimBLE/ESP-IDF I can have a...
theHuanter 04/26/2024 09:22 AM
could the "more data" be the manufacturer data which you can add to the service?
floitsch 04/26/2024 09:44 AM
Really don't know, but even if it is: I would need the nimble function to somehow expose it.
floitschReally don't know, but even if it is: I would need the nimble function to somehow expose it.
theHuanter 04/26/2024 09:45 AM
the manufacturer part is already in the ble library. but I am also not sure what this "more data" part might be
23 messages in total