COM port pin-out

I recently had a nightmare with a COM port header on a motherboard. The board had built-in 9pin COM/serial port next to the VGA connector on the rear IO panel, and a header w/ 9pins on the motherboard labeled COM2. I could not get ANYTHING to function properly thru the on-board header, but everything plugged in to rear COM1 port worked fine. I checked the pin-out against standard COM pin-out schematics and the on-board header matched everything perfectly except for one thing (actually two things): on a std COM port, pins 2 and 3 are labeled RXD and TXD, but on this montherboard, pins 2 and 3 are labeled RXD# and TXD#. Does the "#" make any difference? What does the "#" mean? The motherboard in question is a mini ITX Intel Atom board, model D525MW; we use 'em to build little Point-Of-Sale computers, and many POS systems still use serial/COM based printers. I ended up having to use a PCI serial card and it worked first try, no problems, but that on-board header was just a nightmare and has been disabled in the device manager to avoid any possible problems.

 

I do not think the # makes a difference. I found this com cable for the motherboard. I can't see where it is different from any other.

http://www.mo-co-so.com/COM-Port-Header-Cable-for-Intel-D510MO-and-D525MW-p/mcs-com-5xx.htm

Edit: I found this review and it said if you want to use the com port on the header you have to buy the adapter so I do not know if this is something special or not.

http://www.hardwaresecrets.com/printpage/Intel-D525MW-Motherboard-Review/1389

 

I dunno about the hash,I was interested so Googled a bit and noticed Intel labels them with a hash at the end too in their pin outs.

http://www.intel.com/support/motherboards/desktop/sb/CS-023466.htm#serialinbios

I'm wondering if enabling serial B in integrated peripherals in bios would enabled it.

Good luck,sorry I don't have anything else to add.

 

The BIOS only has a single "Serial Enabled/Disabled" option. I have 2 of the same motherboard, and both have the same problem using the expansion header. The built-in port works perfect, the expansion header either doesn't work at all, or when it works it goes all nutso. I hooked up a POS printer to the expansion header, went to print a test page, and kept printing garbled crapola for a looong time - after 3 feet of paper went by, I powered off the printer! LOL Using a PCI serial card works perfect, so that's what I'll do in the future.

Thanks for researching the issue guys!

 

Hi,

The only real difference in serial ports is theaddress. If t

 

Hi,

My first post and attempt to edit it got clobbered. Let's try again.

The only real difference in serial ports is the address. Google serial port addressing and you should come up with programs to do it for you. If you are a programer I can look up where to write the new address in memory.

Good Luck, Jim