Dependence between connection interval parameter and QDEC

[octopus]

Hi,

I have question related with some parameters of BLE transmision.

Connection interval in my project is set to 10 ms. Peripheral sends a notifications whenever the value of characteristic is changing - this interval is also set to 10 ms. So, I send one notification per single connection interval.

Whats more, I use a QDEC in my project (simplerdy mode) and I set pin P0.03 as a QDEC LED output to generate synchronized clock impulses.

I captured connectionless BLE link from one device to another. Please see a screenshot below:

This is how looks waveform in that configuration - first and second lines are A and B signals from encoder, third is a sampling clock generated by the LED output:

When I disable notification waveform looks like this:

My main question is about LED output on these traces. They are generated according to parameters which I set in nrf_drv_config.h file. However in some periodic, regular intervals the line is hold for a some time in a high state. I guess that this is related with communication and connection interval. If the notifications are set, this time is around 0.9 ms, when they are not, the time is around 0.4 ms (connection interval parameter is still set to 10 ms). You can see these times on above waveforms.

This generates a problem for me, because I cannot count a encoder changes while LED output helds a high state.

Is it okay, that this occurs? Is it possible to decrease these times, if yes, how can I do that?

[Ole Bauck]

So you are disabling the qdec in the interrupt, why? I guess you are enabling it somewhere else in the code or else the LED output would be constantly low. If you enable in the while loop in main you will get the LED output on your traces because the SoftDevice may interrupt the code between disable and enable functions. It should not be necessary to disable and enable the qdec like you do.

[octopus]

From infocenter:

"If the SAMPLEPER value needs to be changed, the QDEC shall be stopped using the STOP task. SAMPLEPER can be then changed upon receiving the STOPPED event, and QDEC can be restarted using the START task. Failing to do so may result in unpredictable behaviour."

So, where in my code should I enable and disable qdec to read measurements properly, but not allow a SoftDevice interrupt LED output?