Connecting/Looping I/O on a custom motherboard

Posted on 2011-09-28
Medium Priority
Last Modified: 2012-05-12

I have a custom motherboard/backplane that uses molex plugs/sockets as I/O. I'd like to take an output from the motherboard and connect it into an input on the same motherboard. That way I'd be able to "emulate" input by sending signals through the output.

Assuming this is even possible (any experience/insight on doing something like this is appreciated), is there any danger in "looping" I/O on a motherboard like this? (I.e. shorting out the motherboard, etc.)
Question by:DG_Dan
LVL 84

Assisted Solution

by:Dave Baldwin
Dave Baldwin earned 400 total points
ID: 36813495
You need to know what the electrical characteristics of the I/O connections are.  You don't want to short out a high current 5 or 12 volt connection thru your motherboard.  It could damage something.
LVL 25

Accepted Solution

kode99 earned 1600 total points
ID: 36819117
Really depends on what this IO this is.  You need to know exactly what the pin out is for the connections.  The voltages are 'likely' going to match for the data.  But as the first poster said you need to know this for sure to avoid damage from mismatched voltage or short circuits if the connection has power pins.

Typically you would also need to cross the connections like a null modem connection.  So when one port says I have data the 2nd port sees it as incoming data.  Take a look at the pinout for a null modem connections,


So outside of data transmit (TD) going to receive (RD) you can also may have to cross other pins like ready to send (RTS) to clear to send (CTS).  So you need to know exactly what the pin out is so you can get the right pins crossed so it works and nothing gets ruined.  Normally mixing up data and flow control pins wont damage anything but you want to be sure there is as I imagine the custom motherboard may be expensive or hard to replace.


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