Is it wrong to send a characteristic notification from inside a timer callback function?

RE: Is it wrong to send a characteristic notification from inside a timer callback function?

mosi — Thu, 02 Jun 2016 12:20:45 GMT

I have based my service on ble_lbs.c

Now I added a check in on_write() to see if the cccd was written to so my app can track if the master has enabled notification or not. And I also disable notification after a disconnect. Looks like it is working.

RE: Is it wrong to send a characteristic notification from inside a timer callback function?

MartinBL — Thu, 02 Jun 2016 12:08:33 GMT

Yes, the error is thrown by sd_ble_gatts_hvx() and it is the BLE_ERROR_GATTS_SYS_ATTR_MISSING error. It probably occurs because you are trying to send a notification/indication to the client before the client has enabled the CCCD. It is not a critical error though. There are lots of Q&As here on devzone regarding error 0x3401. This might be the best answer.

RE: Is it wrong to send a characteristic notification from inside a timer callback function?

mosi — Thu, 02 Jun 2016 11:46:36 GMT

I traced it down and I got error code 13313 (0x3401). I think it was thrown from sd_ble_gatts_hvx().

After searching old questions I found that I must click the Enable Services button on Master Control Panel.

Then it worked :-)

But, is there a way around this so sd_ble_gatts_hvx() wont throw this error if Enable Services is not enabled?

I don't want my app to crash because of this.

RE: Is it wrong to send a characteristic notification from inside a timer callback function?

RK — Thu, 02 Jun 2016 08:27:26 GMT

No it's fine to send a characteristic notification from inside a timer callback function. As long as the interrupt context you are in is less than the SVC call interrupt priority, it's fine. So either that's not the case and you need to lower the timer interrupt priority, or you are getting an error return from one of your functions, tripping the APP_ERROR_CHECK() and that's what's actually restarting the board.