How to externally detect PC Cold or Warm boot?

Projects General Guidance
1

OK, I have a need to detect either a Cold or Warm PC boot/reboot.

The reasoning is simple, I would like to have a Leonardo supply the login credentials for my HTPC.

Right now, it is a "userless" system, it boots straight to the desktop (Windows 7). I order to remotely administer this system (RPD), it need a password protected user account.

So, the concept is as follows:

1). Detect either Cold or Warm boot/reboot.

2). Engage suitable delay (perhaps 10 minutes or more), where the system updates can be applied for the case where a Windows Update required a reboot. The length of this delay is somewhat immaterial, I just need enough time so that I can be sure any housekeeping is complete and be reasonably certain the system is at the login prompt.

3). Send the login credentials.

#2 and #3 are really easy, what I'm having a hard time with is detecting the boot. If I use a photocell illuminated by the system power LED, I can use a resistor in series with the photocell, and measure the voltage with an analog input to "see" the power LED is on. That handles the Cold boot very nicely, but of course won't be affected by a warm boot. So, I'm looking for ideas that can work for either condition, can anyone help?

2

When the PC reboots, the monitor usually looses sync. Are you able to read the video output sync signal?

Weedpharma

3

Weed:

Thanks, for the reply.

I think the monitor sync might be subject to change from driver installs, maybe even "sleep" commands. Given that its all HDMI, it would be kind of a pain to get to the signals as well.