I am considering options to make a small circuit used with ventilation (so fitted into a ceiling) have a watchdog timer. It is not life or safety critical, but it would be inconvenient (but not impossible) to reset them with a small switch on the front that can be pushed with a pin.
I was considering external watchdog chips, but the question is, how do you prevent the chip causing a reset during programming? Details - microcontroller is PIC24FJ256GA702, programmer is ICD4. Each board will need to be programmed after assembly.
This must be a common situation, but I have not found a solution.
I am reluctant to use programming signals from the ICD to reset it until its own reset source is established, and it sounds complicated to implement and could affect programming, but this may be how it is normally done.
Any ideas? What have you done if you have met this problem before?
I don't want to use the internal WD, as I would like to be able to prove it resetting, and I like the idea of a separate device for this job.
This is the circuit I was planning to use. An advantage of the PIC24FJ256GA70X is that the /MCLR pin does not get a high voltage like 13V during programming which would be too much for the WD chip. The IO pin used on WDI is set for open-drain to allow the signal generator input. This device resets after 1.6 seconds.