windows xp - Is it possible to accurately time the reception of serial characters?

06
2014-04
  • rossmcm

    I want to accurately (like - microseconds or better) determine the arrival time of serial characters under Windows (XP).

    I can measure time accurately using the CPU hardware counter easy enough, but the earliest I get to see an incoming character is after it was found its way through all of the layers of drivers, etc.

    What's the closest I can get to the time that the incoming character generates an interrupt on the UART chip - without having to cross over to the dark side?

    x86 Assembler doesn't faze me, but I don't particularly want to write a device driver.

    I have a feeling that USB serial ports would be a problem whatever

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  • Pandincus

    I have a Windows XP Pro SP3 host machine running a Windows XP Pro SP3 guest machine. The host machine has one serial port, COM1, that I need to use in the guest machine.

    When I add the serial port to the guest machine and try to start it, I get the following error:

    Failed to start the virtual machine xxx

Cannot open host device 'COM1' for read/write access.
Check the permissions of that device (VERR_ACCESS_DENIED).

Unknown error creating VM (VERR_ACCESS_DENIED).

    What are some of the things that might be causing this problem? How can I check "permissions" on a serial port?


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  • ytg

    When you can not access a serial port in most of the cases something is using it already. If that is the case you can try to access the port with hyperteminal. If it can not open the port either, you just have to find what uses it, and shut it down.