1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

Can you stop Windows polling the serial ports on boot up?

Discussion in 'Windows & Other Software' started by Chris Wilson, Jun 11, 2019.

  1. Chris Wilson

    Mobster

    Joined: Nov 28, 2003

    Posts: 4,092

    Location: Shropshire

    I have some devices (solid state relays controlling large mains power supplies) running off the true serial ports on my motherboard. I use this set up to remotely switch the supplies on or off via remote desktop using a simple DOS program. However, on boot up Windows 7 64 bit seems to "poll" the ports sending outputs momentarily high a few times. The SSD's, the big linear power supplies and I don't like this! Can it be stopped? Thanks.
     
  2. andshrew

    Wise Guy

    Joined: Oct 25, 2002

    Posts: 2,459

  3. JRS

    Capodecina

    Joined: Jun 6, 2004

    Posts: 13,550

    Location: Burton-on-Trent

    Could also try turning off Serial Enumeration in advanced properties from Device Manager?
     
  4. Rroff

    Man of Honour

    Joined: Oct 13, 2006

    Posts: 62,186

    From my limited knowledge I think you are going to need a more advanced solution - either some kind of blip logic/power on detection circuitry or swapping to something like an Arduino Nano to control the relays.

    Or move the system to another low power always on device.
     
  5. Chris Wilson

    Mobster

    Joined: Nov 28, 2003

    Posts: 4,092

    Location: Shropshire

  6. Chris Wilson

    Mobster

    Joined: Nov 28, 2003

    Posts: 4,092

    Location: Shropshire

    Is that under Device manager - Ports? If so that option doesn't seem available here... Thanks anyway.
     
  7. Chris Wilson

    Mobster

    Joined: Nov 28, 2003

    Posts: 4,092

    Location: Shropshire

    I can't try the aforementioned method until tonight, I'll report back, hopefully it will work, the info certainly suggests it can do the trick, time will tell, thanks.
     
  8. Chris Wilson

    Mobster

    Joined: Nov 28, 2003

    Posts: 4,092

    Location: Shropshire

    Unfortunately this has not worked. Someone elsewhere said it may be hard coded in the BIOS, but the sigs to the Serial Port do not occur until after the Starting Windows logo and just as the password prompt screen shows. it goes through two phases of polling the serial port about 5 seconds apart. I did the bcdedit /enum and after several reboots the off setting had stuck every time. I have also turned off the serial mouse in the registry with no effect. Thanks for the suggestion, any other ideas for me to try please?
     
  9. JRS

    Capodecina

    Joined: Jun 6, 2004

    Posts: 13,550

    Location: Burton-on-Trent

    UART Protection setting in the BIOS perhaps? If you have it and it isn't already on.
     
  10. Donnie Fisher

    Gangster

    Joined: Jun 22, 2018

    Posts: 266

    Location: Vegas baby !

    So does your receiving device simply change states based on a high signal coming into it from the serial port, or is it specific commands send down the line?

    I would agree with the comments that your system reads as though it needs a bit more resilience to random inputs.
     
  11. jpaul

    Soldato

    Joined: Mar 1, 2010

    Posts: 7,358

  12. BattFink

    Hitman

    Joined: Jun 13, 2013

    Posts: 897

    Location: Brighton(ish)

    Back in the day I used to have a old UPS connected to my workstation via serial port, when Windows booted it used to trigger the UPS to shut down, this was due to Windows polling for a serial mouse when it boots.

    Have a look for this registry key:

    Location: HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\sermouse
    Key: Start

    Set the Value to 4
     
  13. Chris Wilson

    Mobster

    Joined: Nov 28, 2003

    Posts: 4,092

    Location: Shropshire

    Thanks, I also tried killing search for a serial mouse, as per the above, but that too had no effect, but thanks for the idea BattFink
     
  14. Chris Wilson

    Mobster

    Joined: Nov 28, 2003

    Posts: 4,092

    Location: Shropshire

    Yes, the DOS app just allows manual on or off, simple commands as far as my (very limited) knowledge allows. the ONLY issue I ever see is upon boot up, after the Windows log on screen.
     
  15. Feek

    Commissario

    Joined: Oct 16, 2002

    Posts: 26,359

    Location: In the radio shack

    I don't know if it's Windows or the hardware doing this. I remember having a serial interface that would always blip the transmitter as the PC booted back when I used to run Windows. In fact, if I reboot my iMac with the radio switched on, it momentarily goes into transmit for a fraction of a second now and that's a 590 connected via USB.
     
  16. Donnie Fisher

    Gangster

    Joined: Jun 22, 2018

    Posts: 266

    Location: Vegas baby !

    Are you able to see what characters are being sent down the serial line ? With what you've disabled, it reads as through there is another service which is polling the com ports during start up.

    Is the machine an old one thats had a lot of various programs and things installed / uninstalled over the years that might have left a service which has used the com ports and is still being loaded on startup ?

    Does it do it if you boot into safe mode ?
     
  17. Chris Wilson

    Mobster

    Joined: Nov 28, 2003

    Posts: 4,092

    Location: Shropshire

    I haven't tried booting in to Safe Mode, but I will. To be frank I saw my backside with it and made a little 5V linaer power supply in an alloy and now use an RF switched 13 amp plug socket adaptor to power the 5V supply and in turn that switches the big solid state relay. i can't operate it away from home, but at least it doens'y have a mind of its own ;) i will try Safe Mode though, but further reading shows many others have this (including Mr Feek), and it was impossible to tame. Thanks for the replies everyone!
     
  18. Rroff

    Man of Honour

    Joined: Oct 13, 2006

    Posts: 62,186

    Definitely worth looking into something with a microprocessor like the Arduino (the Nano has a fairly simple interface and lots of output options) or RPi for this kind of thing.
     
  19. jpaul

    Soldato

    Joined: Mar 1, 2010

    Posts: 7,358

    I'd posted previously on fake chinese SSR's catching fire ... so hope you got a bona-fide one.
     
  20. Chris Wilson

    Mobster

    Joined: Nov 28, 2003

    Posts: 4,092

    Location: Shropshire


    I am probably too old to bother getting in to programming stuff, but I certainly agree they are extremely useful gizmos! Thanks.