Power-On Self-Test (POST)

[rWAVE]

I am playing with an 08M and wondered about performing a POST of the controller and associated components.

Since my Picaxe is "sleeping" most of the time, I thought it might be cool upon power-up to check various functions (microcontroller, clock chip, etc), turn on an LED if tests pass, and then proceed to execute the application.

If this makes sense, I would appreciate some thoughts on which basic functions should be tested to give a "reasonable" assurance that each chip is functioning properly.

 

[hippy]

I'm not sure it would even be worthwhile or even easy to do.

If the PICAXE has failed, then it won't work properly and can't indicate it has failed itself. To determine that, you need a separate mechanism to indicate it's not working and that means using additional circuitry and monitoring, and that too may be just as likely to fail, or more so.

The easiest option is probably to have the PICAXE turn a LED on and off repeatedly, and if it's doing that, assume it's working.

Determining if the circuitry surrounding the PICAXE is working is just as hard, and will require applying stimuli and checking responses.

Unless safety or mission critical it's unusual to have any POST at all. It's usually good enough to have it working or find, "Oh, it's broken !", and then start looking as to why.

 

[SD2100]

You could make a watchdog timer to monitor the 08M, just pulse an output to keep the watchdog happy, if the watchdog fails to receive pulses on a regular basis it resets the 08M. You could count the number of reset attempts and trigger an alarm if the 08M failed to respond. You could use another 08M to do this and they could look after each other. But these things appear to be very reliable so not really needed unless it's somewhere really remote and it has to look after it'self.


Edited by - Phil75 on 19/05/2006 19:11:28