[Xastir] I finally got it!

[Michael Lewis]

  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.
>