I need help with how to change how Windows 7 controls a serial COM1 port default settings. I use a very simple serial cable to control special external hardware with. Fsx Cabin Crew Announcements more. The serial cable only uses the RTS, DTR and GND pins of the cable and does not require any special hardware drivers. I have used the device on several prior versions of Windows 95 through XP with no issues at all with the serial ports. With Windows 95-XP the serial COM1 port had RTS and DTR lines set 'off' by default. I just upgraded to a new computer with Windows 7 and now having an issue with the serial port. Cracked Steam Setup.
For my issue, I need to have the serial port be 'off' by default until the control software loads and specifically opens the serial port to turn the external device 'on'. Using a serial port data tester (has lots of green and red led's) I can see that as soon as Windows 7 boots up, it automatically sets the serial port DTR, RTS and TD lines as 'HOT' (high voltage). This is not acceptable as it activates the external hardware before the control software is loaded! Likewise when the control software is closed and the serial port is released back to Windows 7, the serial port DTR, RTS and TD lines are again set as 'HOT' (high voltage) by Windows. Computer: Dell Optiplex 745 Windows 7 Pro 64 bit with SP1 installed Serial Port on motherboard: Intel ICH8/ICH8R LPC Interface Controller 2810 Serial Driver: Microsoft 6.1.7600.16385 (is up to date) Settings for COM1: ------------------- Baud Rate: 9600 Data Bits: 8 Parity: None Stop Bits: 1 Flow Control: None I have spent hours looking at Device Manager/port settings and trying to find anything online with no luck. Is it possible that this is due to how Windows 7 plug-n-play handles the serial port?