Has anyone ever seen any hardware that will cycle the power input to an Arduino? What I want to do is buy something to perform a complete reset of the Arduino as a watchdog reset isn't always enough to get a 'stuck' unit to perform. Please don't suggest a switch or pulling the plug I want to do it programmatically.
There's two ways you can go about this.
One is to use a dedicated watchdog chip - Maxim has a selection: http://www.maximintegrated.com/products/supervisors/watchdog/
The other is to use a second Arduino (or other small microcontroller) to act as a watchdog. Program it so that it expects some activity on a pin which resets a counter, and when that counter reaches a threshold it shuts off the power briefly to the master Arduino (which could be controlled by a P-FET, or a relay, or whatever method you like). The master Arduino then just has to ensure that it toggles the required IO pin regularly enough.
You could also use a CMOS 555 timer (ICM7555) as a monostable driving a p-channel
high-side power switch?
Something like the circuit on this page, but drive the gate of a logic-level p-channel MOSFET
instead of a buzzer, and set the time constant for 1/10 second or so:
http://www.technologystudent.com/elec1/5554.htm
The 7555 is far superior to the 555 in terms of decoupling requirements
and supply range and power drain, BTW, I prefer it.
Thanks for the suggestions guys, I was hoping I could buy something off-the-shelf. I guess the idea of a second Arduino comes closest but it does seem a little overkill.
pwdixon:
Thanks for the suggestions guys, I was hoping I could buy something off-the-shelf. I guess the idea of a second Arduino comes closest but it does seem a little overkill.
So go for something smaller. ATTiny?