[mythtv-users] Controlling a cable box

Graham myth at c0redump.net
Mon Jul 21 20:17:13 EDT 2003


On Mon, 21 Jul 2003 08:23:30 -0700, Ignacio wrote:

>Hi, yesterday i found out a few things about my digital cable box:
>1. It has a serial port
>2. It has an R blaster port

The use of the serial port and the IR blaster port depend heavily on the software that's actually been loaded on the DCT (2000?) box. This is customized by the cable company before the boxes are 
rolled out to customers, so different cable companies have different features.

On the DCT 2000, the IR Blaster port is designed to control a VCR unit, so that the DCT 2000 can start and stop recording on the correct channel. This means that the cable box can change it's own 
channel, then tell the VCR to record. It's called an "IR Blaster" as it's designed to "flood" a room with lots of IR, so that devices will operate even if they're not in direct line of sight.


>3. Would these transmitters work
>http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=2743486907&category=44961

This transceiver looks like it just connects an IR transmitter and IR Receiver to the TX and RX lines of the serial port. Unless your recieving device happens to support IrDA or other protocol that uses a 
standard serial port, then this won't work.

>http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=2743025215&category=44961

This looks like a similiar idea. Probably a small microcontroller connected to the USB bus, with a UART onboard to handle the serial IR stream. I suspect this wouldn't work either, but that would depend 
on the firmware on the microcontroller. The problem with most of the IrDA devices is that they have too much intelligence, so it's not possible to actually get at the IR stream itself! Unfortunately this 
makes them rather unsuitable for use as an a consumer style IR device. This is why there are relatively few devices that can do this sort of task well!

Graham




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