TG626:
That's a bit of a "strict" interpretation of what I wrote. Some thing triggers that LED in, that something is commanded by the OS, therefore if you can tell what command caused the LED to trigger, and can monitor that command you can, in effect, tell the status of the LED.I offer as example that there is at least one app that will put an HDD "light" in your status bar, and even flash a "lock" LED of your choice on the keyboard, but I don't like having such things running on my PC.
It is therefore obvious that ON THE PC, UNDER THE OS, it is absolutely possible - it therefore should be possible to have an applet running under Windows that sends messages to a USB connected device and cause some activity to occur.
My real intent was to find out if that could be accomplished WITHOUT having software on the host machine, in a similar manner as determining the LOCK LED status.
Fair enough!
Do you have any memory reserved for disk cashing? Do you know how that is used? Access to the cash is for all disk reads and writes. IF the requested 4k disk block is not in the cash, an new 4k block is read for that data. If on writing a disk record that will fill a 4k block, that block is written. Those are the only times a physical disk access is made. There is NO other relationship between physical disk access and a programs file read/write.
Do you recall shutting down your computer with programs still running? You are usually reminded to shut down the programs so you won't loose the data that was written. I see WIN 10 has changed so the message to tell a program to shut down also flushes the disk cashes. Now we don't see the warning.
So, I don't see your reason for wanting to know about physical disk activity.
Paul