How to sample data with app_timer in IRQ but process outside interrupt?

Question

I want to process queued sensor data collected at a fixed interval (every 100ms) via TWI in the background/main loop. In the example ble_app_hrs , timer expiration callbacks run directly in the IRQ. 
 APP_TIMER_INIT(APP_TIMER_PRESCALER,
 APP_TIMER_MAX_TIMERS,
 APP_TIMER_OP_QUEUE_SIZE,
 false);

err_code = app_timer_create(&device.sample_data_timer_id,
 APP_TIMER_MODE_REPEATED,
 OnSampleDataTimerExpired);
APP_ERROR_CHECK(err_code);
 
 That fourth, false parameter of APP_TIMER_INIT is supposed to indicate whether the scheduler is desired, otherwise the callback runs in the IRQ. I need this enabled if I want the callback to run in the main/background loop (NOT THE IRQ) but am unsure how to use the scheduler and whether I can run one timer callback in IRQ and another in background?

Stefan Birnir Sverrisson · Accepted Answer

Hi 
 As you have pointed out, the app_timer either use the scheduler for all timers or none. You could also mimic the functionality of the app_scheduler by simply setting a flag in your app_timer callback and poll for that flag in the main loop, i.e. when the flag is "true" you perform your TWI operation in main loop.

How to sample data with app_timer in IRQ but process outside interrupt?

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