I have a temperature sensor that sends data to the internet via the Ethernet shield. The watchdog timer keeps everything running as it did sometimes lockup. Rarely I have to press the reset button to kick it back to life after a power cut. I am going to install another in a very remote location so presing the reset button is not an option. Being a software guy I thought about having an ATtiny85 saying hello to the Uno every 5 seconds and if it did not get a reply would fire off some sort of reset circuit to get the Uno back online. Is this possible and if so what sort of hardware would be required?
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I wonder if you you can not just as well use the watchdog timer in the 328 micro. Your code has to 'say hello' to it e.g. every 5 seconds or it will reset the micro.
Am already using the watchdog timer and it works really well. I send out the date of last power up and it does reset itself about once a week. However it sometimes hangs, for some unknown reason, once in a blue moon and does require someone to press the reset button. I thought an ATtiny85 could obtain a reply from the Uno, once every 5 seconds and if no reply fire off a reset circuit - ideal for a remote location.
SpyCatcher2k also kindly replied and suggested a cap and a resister, so will look up the sort of circuit he means as being a software bod have no idea about the hardware side of things. That's what makes the Arduino so interesting as it is a super learning platform - fascinating!