I have it in front of me now.. with it plugged into the USB port
Pins 5 & 2
6.4 V
Pins 5 & 3
0V
On 9/17/2010 3:36 PM, Curt, WE7U wrote:
On Fri, 17 Sep 2010, Michael Lewis wrote:
Yep I found that same site
the null modem I got from ebay months ago no clue what type pf null
modem cable it is.. I just know when connected to the splitter and
with it's null modem I can't connect to the tracker at all.. I have
no other serial cables here so I had to buy a 6Ft cable off ebay last
night for around $2.49 free ship.
Do you have a meter? Analog or DMM? If so, you can check between
pins 5 (GND) and 2 on a DE-9 (contrary to public opinion, it's a DE
and not a DB for a 9-pin). Then do the same for pins 5 and 3. 2
and 3 are your TXD/RXD pins, which are the ones your data goes down
in each direction. If pin2 on one connector is being driven (+3 to
+12VDC or -3 to -12VDC) then you don't want to connect it to another
connector that also has pin 2 driven. In that case you'll need a
null-modem cable or adapter to connect the two.
If pin 2 is driven on one, and pin 3 is driven on the other, then
you can connect the two.
It can be a LOT more complicated than that with all the possible
cable wirings out there, but those two pins are the main ones to
worry about. For DB-25 cables (yes, DB now instead of DE), it's
pins 2/3 and pin 7 for ground.
What you might want to do if you play around with RS-232 quite a bit
is get some null-modem adapters and an RS-232 LED breakout box.
Using the breakout box you can plug it into one cable and see one
LED light up, plug it into the other and see a different LED light
up, and know that you can connect the two cables. This is the type
of thing I'm talking about:
http://www.scancat.com/minitstr.html
Radio Shack used to sell the adapters and the LED breakout box. I
have several plus various 9-25, m-m, f-f, and laplink type cables so
I can pretty much adapt to anything at a moment's notice.
_______________________________________________
Xastir mailing list
[email protected]
http://lists.xastir.org/cgi-bin/mailman/listinfo/xastir
