[mythtv-users] DirecTV (RS232-to-RJ11 cable) -- I think I figured out my problem!

[Ray Olszewski]

Well ... from what you describe, I have two ideas, with the second one kind 
of out on the fringe.

1. Try connecting RX to RJ22 pin 3, as you speculate.

2. Consider the possibility that you are reading the pin positions on the 
RJ22 upside down. (You'll recall I agreed with your guess about how to read 
this, but I also reminded you that my doing so just made it a shared guess, 
not correct.) Then you have TX and SG reversed, and RX on the (supposedly) 
unused pin. RS232 signalling is just wacky enough that swapping TX and SG 
might still let TX work, but RX wouldn't work in this setting no matter 
what you do.

If neither of these ideas pans out, I'm left with suggesting you look for 
one of those old RS232 troublshooting boxes, that had red and green LEDs to 
detect which pins were active. (I don't know where to find these today; 
mine is probably 10 years old.)

Good luck. I'd like to see this procedure get well documented.

At 11:30 PM 6/9/2003 -0400, John Klimek wrote:
>Ok, here are my findings so far.
>
>DB9F pin assignment is definitely as follows:
>5 4 3 2 1
>  9 8 7 6
>
>RJ22 pin assignment seems to (definitely?) follow:  (when looking at the
>bottom, pin-side)
>Pin-1
>Pin-2
>Pin-3
>Pin-4
>
>Following the pin assignment, I've connected:
>(RJ22-to-DB9F)
>1 - to - 5  [ground]
>2 - to - 2  [receive]
>4 - to - 3  [transmit]
>
>Here is what happens:
>
>1)  If I DO NOT connect the RECEIVE line (2 - to - 2), I can transmit to the
>receiver PERFECTLY.  The receive changes channels, etc, etc and works
>perfectly fine.  Of course I still get "a Timeout" response from the receive
>because the RxD line is not connected.  However it will still change
>channels.
>
>2)  If I DO NOT connect BOTH the RECEIVE and the GROUND line, whenever I
>transmit to the receive it will change to WEIRD channels and do weird
>things.
>
>3)  If I connect ALL THE WIRES, as soon as I plug the cable into the
>computer and the receive, my satellite receiver will turn itself on and off
>constantly.
>
>I believe my problem is DEFINITELY located in the receive line.
>
>If I can transmit fine (with TxD and Gnd connected only), then I think its
>safe to assume my RJ22 and DB9F pin assignments (and connections) are
>definitely correct.  However once I hookup the RxD line, I immediately get
>problems ranging from receiver self shutdown/reboot or I get "Timeout"'s
>when I send
>
>Also, I measured my cable and it's 50' (I thought it looked longer than
>that).  So, if I can transmit fine then I'm thinking I have one of two
>possible problems:
>
>1)  The satellite receiver is not strong enough to send a signal back to the
>computer over the 50' of cable.  Can I test for this any easy way?  It's
>hard to rewire my cables espicially if I had to chop the length back down.
>
>or
>
>2)  The diagram is screwed up and I'm actually suppoed to connect RJ22 Pin 3
>to DB9F Pin 2.
>
>Has anybody else built a cable like this that can possibly help?
>
>Ray, thank you so much for helping me.  If you have any other ideas please
>let me know.  I know I'm very to getting this to work.
[old stuff deleted]