Custom service design: irq vs timer

[michurin]

I have several asynchronous аperiodic sensors with their interrupt handlers. My service should gather the data from those sensors and do some math. The outcome of this math may be cause of alarm. Delays in few seconds are acceptable. Losing some alarm conditions are also fine - I need continuous event. I leaning towards launching my service via timer and not when one/each sensor interrupt has occur. The battery life is more important than some delay. Your suggestions please.

[Stefan Birnir Sverrisson]

I still have the feeling that you are asking questions I have already answered. Anyhow, I can point you to a code example which shows how to wake up the chip with a press of a button. By pressing one button, the device is put to sleep, and by pressing another button you can wake the device up again, github.com/.../nrf51-powerdown-examples Look at the system-on-wakeup-on-gpio example. If you would use SPI slave to collect data from a sensor, the event is triggered when the sensor sets CSN line high (see SPIS chapter in the nRF51 Series Reference Manual). For see how this is done, look at the spi_slave_example in the nRF51 SDK. When the SPI transaction is complete and the SPI master sets the CSN line high, you will get a callback into the spi_slave_event_handle where you can fetch your data that was received on the MOSI line.

[Stefan Birnir Sverrisson]

I think it is a good option to collect sensor data into a buffer and then periodically process the data. You can do that with starting a RTC timer that periodically wakes up the chip to perform the calculations.

[michurin]

"I think it is a good option to collect sensor data into a buffer and then periodically process the data." I think so too. You're saying RTC because other timers are in the sleep mode?

[Stefan Birnir Sverrisson]

The overhead of waking up and going to sleep is small, at least if going into System On low power mode, the overhead is bigger if you enter System off low power mode, but in System off you will draw less current than in System On. So if you wake up once a second or 10 times per second from System On does not matter that much, the main thing is to make your code efficient so that the execution of it takes minimal time, to stay awake is what will cost you power.

[michurin]

"...but in System off you will draw less current than in System off." Is this typo?