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Topic: Need help building adapter (Read 794 times) previous topic - next topic

0x02b_a_newbie

So my new motherboard doesn't have a serial port on the back panel (gasp) but it does have a COM port on the board itself in the form of a 10pin DIN.
So i thought to myself, perfect time to bust out the MAX235 that's been sitting around and build an inline adapter to have serial TTL broken out on the front of my computer (through a firewire port I don't use)

So looking at the diagram on the mobo manual I get this pinout
1 - NDCD-
2 - NSIN
3 - NSOUT
4 - NDTR-
5 - GND
6 - NDSR-
7 - NRTS-
8 - NCTS-
9 - NRI-

I broke out NSIN, NSOUT, and NDTR-
When hooked up to the max235 (and an LEDs on the 12v and 5v sides) I get inverted signals.
NDTR- and NSOUT stay low while on the other side they're high, unless data is transmitted then they flicker. If I want to send data to the COM port, I need to bring RX low so NSIN goes high.

Is this normal TTL logic or inverted?
Basically, If I hook this up to my RBBB will I blow everything up?

0x02b_a_newbie

I never thought they were TTL. Perhaps I was ambiguous in my first post, I wanted to take the RS-232 port on the mobo and convert it to TTL then break that out on the front of my PC (either by an unused firewire port, or my own design), I was just incorrect in thinking RS-232 used positive logic and that the TTL side was inverted.

As I had described it, it was working perfectly, so I'm soldering it up on some perfboard now...

Will post pics when I wake up

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