Serial set top box control (long post warning)

I'm new to TiVo and this is the first thorn in my side:

I know the OzTivo image states that you shouldn't be using serial to control set top boxes but I just can't resist...

The TiVo's built in bi-directional protocols MPG/APG although they are simplistic and give out the right information for the job, they're still incompatible with my set top box (topfield).

I've found that the 'myworld' application is writing the commands to the serial port /dev/ttyS3 which is about where I hit a dead end.

Unless anyone knows any different it doesn't look like you can't change what it's sending out, presuming this is the case, this only leaves the following options:

1: use some kind of software translation layer, i.e. write a kernal module for myworld to open which 'looks' like a serial port, translates the commands and writes them to the real serial port
2: use a hardware translation layer, like some kind of external micro (ick!)
3: skip the MPG/APG functionality altogether and have some kind of shell scripts which write the correct commands out of the serial port, this would be dead simple but I don't have any idea how such a script would be triggered on a channel change
4: I've completely missed something obvious, and am way off with all of the above rant and this is actually a simple to thing to do

Quote:

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Originally Posted by inaxeon

3: skip the MPG/APG functionality altogether and have some kind of shell scripts which write the correct commands out of the serial port, this would be dead simple but I don't have any idea how such a script would be triggered on a channel change

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Looks like this is the approach used here:
http://minnie.tuhs.org/twiki/bin/vie...ialPortControl