[mythtv-users] another DCT2000 query

[Ian Forde]

On Wed, 2004-02-18 at 21:27, Ray Olszewski wrote:
> Thanks again, Ian. Just responding to clarify a couple of things you 
> wondered about. I'd welcome any added advice you have ... but I'm also 
> making progress here as things stand.

No problem - responses inline...

> It sent some packets, which is how I confirmed that the DCT's serial port 
> was working. But the internal documentation for the Python program is a bit 
> sparse, and I'm not a Python programmer anyway, so I couldn't figure out 
> how to get it to send the specific instructions I wanted it to send. Is 
> there someplace that describes what command-line arguments this program 
> responds to? I didn't find one in the stuff I had with it.

S'okay - I'm not a Python programmer either.  And since I haven't looked
at this code for a WHILE, I may be a little rusty.  (Most people I
believe are now using the C code that Jim Paris wrote.  He's got more
error-checking and has figured out the response codes.)  Having said
that, I wrote the documentation for the script (check the README file). 
The logic is simple.  First, some functions are defined.  Checking for a
string parameter versus a numeric parameter, getting a response from the
serial port, sending a code to the unit, etc...

Next, we parse the parameter.  There's some code that's unused by myth
that lets you mute the cable box, go back to the last channel, etc,
based upon if the script if given one of several letter arguments
instead of a channel number.  If it's a letter argument, we figure out
the code, open the serial port (line 174) and send it to through the
port (line 175).  Otherwise, we pad the number to 3 digits, create a
concatted string to send out, open the port (line 196), and send it to
the box (line 197).

So basically, the arguments are:

l,m,f,u,d or a channel number.  No dashed options whatsoever...

> [...]I have no doubt it is enabled. I'm using it (under manual or cron-script 
> control) now.  The question I can't resolve is whether it does two-way 
> communication.

Okay - this I've run into.  Turned out I had a bad serial port on myth
box.  I kid you not.  Try it on another serial port or with a different
serial cable.  (You can even use a 9-pin RS232 to RJ45 adapter that
comes with Cisco routers with a straight through Cat-5 cable to a RJ-45
to DB25 cable used for Sun consoling.  Stick a null modem on that and it
might do the trick...)

> 1. The C program cannot get a response in its initialization section.

Yep - consistent so far...

> 2. The Python program claims it gets responses, always the same packet (or 
> always the same in response to a channel-number packet, anyway). But since 
> I don't have any docs on how the DCT is supposed to respond on the serial 
> port, I don't know if it is getting real responses of something Python'ish 
> that I don't understand.

Reboot the PC, power off and on the cable box, and try again.  Bear in
mind - I have the serial hack for my Tivo as well, and if my Tivo
reboots (due to power failure, etc...) I have to power cycle the cable
box otherwise the Tivo stops accepting remote codes due to some
deadlock.  Turns out Tivo likes to response codes too.  Thus, it might
not be a bad idea to script in a power-cycle code of the cable box when
mythbackend starts.  The C code will do this if it can't get a channel
change through after a certain number of attempts.

> 3. The Perl program I wrote to change channels does not get responses from 
> the serial port. Outgoing packets to the DCT go through fine, though ... 
> which contradicts the claim in the comments in the Python program that the 
> DCT's reply has to be read before the DCT will accept another packet.
> 
> 4. A neighbor has the same cable service and DCT model, and a TiVo. He 
> tells me his TiVo can change channels but cannot do anything that requires 
> it to get information from its DCT (like know if the serial cable is 
> connected ... my friend's example from bad experience).

That may be a red herring.  If he's got a D-Tivo or a standalone Tivo
with the serial hack, his serial cable is being used.  But there are
many out there who have a serial cable connected, believing that it
works, when in point of fact it's the internal IR transmitter in the
Tivo that can penetrate wood (believe it) to change channels in the DCT
box.  If he's got a standalone Tivo, make sure that he's got the hack
that gives him the serial cable menu option.

> You see why I am uncertain.

Yepper!

	-I
-- 
                       __________________________________
                       Ian Forde, RHCE, CCSE, SCNA, SCDME
                       CYTBeN, Inc.
                       ian at duckland.org / ian at cytben.com