Com ports hang under windows 7.

[William Gaatjes]

Hi,

i have one authentic com port and one usb to serial converter com port.
I tried this with the programs realterm and terminal.

usb to serial converter :
When i connect pins 2 RXD and 3 TXD it works.
I can type in text and i see the characters appear.
When i connect my mcu developmentboard to spit out data, the com port just locks up. I disconnect my dev board and when i connect pin 2 and 3 again i get nothing at all. I need to open and close the port again.

authentic com port :
When i connect pins 2 and 3 it does not work at all.

Since the beginning when i just started using W7 i have had issues with my com ports.

Does anybody have some good advice.
I think i need to get my oscilloscoop and check all the levels.

 

[John Connor]

It could be the usb to serial converter. What kind is it. I heard the PL2303 works well.

 

[Steltek]

Is the software you are running attempting to directly access and read data from the COM port hardware instead of going through a hardware driver?

If so, the OS is causing your problem -- Windows XP and later, by design, block direct hardware access. It isn't something you can work around, either.

That is the reason you will see lots of expensive older computerized machinery out there which is still linked to software on old computers running Windows NT (or even WinME/98SE or earlier) -- those OSes didn't have that restriction, and the software thus can't be made to run on a later "modern" version of Windows.

 

[Mushkins]

Is the software you are running attempting to directly access and read data from the COM port hardware instead of going through a hardware driver?

If so, the OS is causing your problem -- Windows XP and later, by design, block direct hardware access. It isn't something you can work around, either.

That is the reason you will see lots of expensive older computerized machinery out there which is still linked to software on old computers running Windows NT (or even WinME/98SE or earlier) -- those OSes didn't have that restriction, and the software thus can't be made to run on a later "modern" version of Windows.

Aye, com ports are a huge PITA on modern Windows platforms.

When in doubt, Linux live-cd. At least that rules out a software issue.

 

[sm625]

Try messing with your flow control options. You shouldnt need any special driver if all you are doing is receiving data from your dev board to a dumb terminal.

But if your devboard has its own software and that software is doing the sending and receiving, then yes its driver may not be workign properly. But from what you said that doesnt sound like the issue. You should clarify... you are just receiving characters from your devboard onto the same exact terminal program you were using when you shorted pins 2 and 3?

 

[William Gaatjes]

It turns out my bracket is faulty and i had some jumpers on my dev board on the wrong position. I had forgotten i changed the jumper settings on my dev board.

My authentic comport does not work and that is probably because of the bracket i bought. Perhaps pin1 is not pin 1 on the connector i have to check that this weekend. I assumed the red wire is pin 1 but it might be reversed.

In the past, my prolific usb to serial converter would hang up because of my attempt to write a cdc device with my sam7s256 dev board. Every time i try my buggy usb cdc( usb to serial comport) code on my dev board, the usb hub would hang up and my prolific usb to serial converter would stop working after i plugged in the usb plug from my dev board. I solved that by plugging the prolific usb to serial converter into another usb port connected to another usb root.