Writing to Timer1 EVENTS_COMPARE register doesn't seem to work

[eBrock]

The nRF52810 datasheet shows the EVENTS_COMPARE register as RW, so I'm assuming that I can write to it.

But when I write to it, nothing happens.

Example.

I set up the timer to generate an event at 10 seconds and use a While statement to wait.

while (NRF_TIMER1->EVENTS_COMPARE[TMRCC1] == false);

During this 10 seconds, I wait for an interrupt from an incoming ESB packet.

In the ESB handler, I write to the EVENTS_COMPARE register so that when the handler is done,

the program doesn't have to finish waiting for the remainder of the 10 seconds.

NRF_TIMER1->EVENTS_COMPARE[TMRCC1] = true;

However, this doesn't do anything as the program still waits until the 10 seconds is done.

Any tips would be greatly appreciated.

[Edvin]

Hello,

So you are not using the NRF_TIMER1 itself to trigger the capture compare?

Are you sure that you get the event on the ESB?

Wouldn't it be easier to use an app_timer to do this? I believe so, but you may have some reason to not use that.

Have you set the INTENSET register? I don't know whether this solves anything, but according to the spec, you can't generate a Compare event by writing to the register manually. Reading from infocenter's section about TIMER:

"A COMPARE event is generated when the Counter is incremented and then becomes equal to the value specified in one of the capture compare registers"

I suggest that you use a volatile variable in the ESB handler, and check:

esb_handler()
{
    esb_triggered = true;
}

while ((NRF_TIMER1->EVENTS_COMPARE[TMRCC1] == false) || !esb_triggered));

BR,

Edvin

[eBrock]

To be more specific about the application, this 10s wait period is only done upon first powering up the device. It allows a 10s window to perform some configuration operations. So, low power is not important during this period.

It sounds like the EVENTS_COMPARE flag is only allowed to be generated by the CPU and not by a write to the register?

[Edvin]

It may be. However, I believe using the app_timer is more suited for this. If you use app_timer_start() to start the 10 second timer, and then app_timer_stop() inside the esb event, then you can do pretty much the same. 

It may be due to some optimization issues. You can try to disable this, but again, I suggest that you set a volatile variable in the ESB event, and add this to your check. 

pseudo code:

volatile bool check_configuration = false;

esb_callback()
{
    handle_callback();
    check_configuration = true;
}

main()
{
    ESB_Setup();
    TIMER1_setup();
    TIMER1_Start();
    while ((NRF_TIMER1->EVENTS_COMPARE[TMRCC1] == false) && (check_configuration == false));
    // Continue ...
    do_stuff();
}

[eBrock]

This works. Thanks for the help. I would have never thought to try this.