Where is the function which sets the cccd?

[Mitch996]

Hello, I'm using an android device to set cccd, it worked when I was running the project on nrf514xx @s110, it no longer does on nrf52840 S140, so now I wanna make sure the program actually dont skip the part that sets the cccd.

So where in the library API can I find it? Which switch case? Which API function? I imagine it is a part of a gatt call back somewhere, but I can't quite tell where.

I hope it's not deeply hidden in the SD and it's impossible to locate.

Also, the other question I asked here can provide some more background:

devzone.nordicsemi.com/.../

[endnode]

Hi Mitch, how you describe it this seems to be more Android problem. What radio sniffer trace says? Is android phone really writing proper 16-bit value to CCCD handle? Is it using Write Request not Write Command (which seems to be forbidden by BT SIG spec for writing to CCCD and so Nordic enforces it in their latest soft devices (see this Q&A thread for more))?

Otherwise when it comes to S140 API you should wait for BLE_GATTS_EVT_WRITE and filter it by target handle and value and act accordingly.

[endnode]

Yes, this is how it works and always worked. You cannot "enable CCCD" from GATT Server side any time you want, it MUST be enabled from GATT Client. It is written in BT SIG specification and hasn't changed since v4.0:) So if you would try to send HVX on S110 (whatever legacy version) you would anyway get error code back from SD if CCCDs are not allowed yet. Now if you have looked for this Write to CCCD handle and enabling Notifications in your app or you just played Russian roulette by fired HVX and got lucky I don't know. One important point: if you use BT SIG Security Manager (layer) and bonding (mechanism) then GATT Server is obliged to keep CCCD state over disconnection so theoretically if your phone bonded and enabled CCCD once it was never needed to keep track of CCCD, it will be always the same (Notifications enabled).