Had a chance to sit down and muck around more with the M2-ATX. Specifically with the ABCD jumper settings controlling the shutdown timing.
Currently powered off a desktop ATX power supply (rated 14A @ 12V).
* The timings for the shutdown and hardoff are not precise. Not to say that they do not work or are not up to the task. They are pretty good actually when you consider that they are based on low-cost RC-type oscillator timing circuits (or on the PIC internal oscillator). Expect up to 15% or so on either side of the documented timings. For a carPC application, this is more than adequate. However Andrei may wish to consider a note in the manual on the tolerances of the timings for those more familiar wth the style of datasheets.
* The next version (M3-ATX?) may wish to consider the implementation of an addition input - preferably 5V TTL/CMOS compatible - which is logic-OR with the 12V ACC sense input. This would be a benefit for us endusers who want an easy way of manually overriding the 12V ACC input.
* The ACC input line may need a pull-down resistor to ground. (Or is it implemented already?) I noticed that when I disconnect the ACC sense line from 12V and left it floating, sometimes the M2-ATX does not successfully detect and provide a shutdown pulse to the mainboard. However when I disconnect the ACC sense line from 12V and ground it (touching the PSU case), the shutdown logic works reliably as expected. Any recommendations of a value for the pull-down resistor from those more familiar with the M2-ATX design?