Update timer speed once connected

[StephaneJ]

I have a custom Characteristic in my GATT that is sending data in Notify mode every 30ms.

In my firmware I use timer to do this with something like this :

#define RTC1_TICK_DURATION		31
	
#define TIMER_ONE_DURATION   		33 // 30ms																/**<(deflt:1000)[ms] sending/measurement cycle duration for 1s cycled characteristics*/
#define TIMER_ONE_TICKS_NB 		(TIMER_ONE_DURATION * 1000 / RTC1_TICK_DURATION)


err_code = app_timer_start(m_TimerOne_id, (uint32_t)TIMER_ONE_TICKS_NB, NULL);

Everything is working great but sometimes, randomly, my app using BLE or my laptop using Web BLE (so two different device with two different source code with the same behavior) are unable to retrieve value for this Characteristic. They are able to connect to my device but no Characteristic value is send.

I tried to change the interval from 30ms to 90ms and so far I am not able to reproduce this issue so it lead me to think that the speed can be the source of the issue.

How would you deal with that ? Is it possible to notify at a low pace, then one second after a connection is made, increase the speed ? Or better, when someone subscribe to the Notifying Characteristic increase speed, when it disconnect decrease speed ?

Thanks !

[Simonr]

Are BLE_GAP_CP_MIN_CONN_INTVL_MIN and BLE_GAP_CP_MAX_CONN_INTVL_MIN what the comments state 100ms and 200ms? In that case the problem is likely that your application sends notification inbetween and during connection intervals. You should decrease these to lower values. I.E. 10 and 30 ms, to make sure that your device is able to connect before sending the notify 

Did you have any luck looking into the GitHub example I linked to?

Best regards,

Simon

[StephaneJ]

Do not pay attention to the comments they may not be right !

BLE_GAP_CP_MIN_CONN_INTVL_MIN and BLE_GAP_CP_MAX_CONN_INTVL_MIN are standard for me, so they refer to ble_gap.h :

#define BLE_GAP_CP_MIN_CONN_INTVL_MIN            0x0006  /**< Lowest minimum connection interval permitted, in units of 1.25 ms, i.e. 7.5 ms. */

#define BLE_GAP_CP_MAX_CONN_INTVL_MIN            0x0006  /**< Lowest maximum connection interval permitted, in units of 1.25 ms, i.e. 7.5 ms. */

So in your opinion my min connection interval should be 10ms and my max 30ms ?

In my case I have 7.5ms for both min and max and this could be the issue ?

Yes I checked the Github but not tested yet. If I can resolve this issue with the connection parameters it would be a huge advantage so I prefer to explore this path first :)