Directv switching?

[jvvh5897]

I've been taking apart DTV box code for a project and while looking at drd430 box code found that they used something rather like diseqc switching for something. Looks like they setup a three byte message on the cx24110 tone system with 0xe1 as first byte, then send 0, 1 or 2 and finish with 0x00. In diseqc switching 0xe1 is used as a repeat command rather than a "master first byte". I also see that while for a little while they set up the system to use diseqc frequency send, they end up setting it to do just the message envelope rather than 22 Khz tone. Does this look right or has anyone done some playing with that provider's boxes to know more about the format?

[dishuser]

I've been taking apart DTV box code for a project and while looking at drd430 box code found that they used something rather like diseqc switching for something. Looks like they setup a three byte message on the cx24110 tone system with 0xe1 as first byte, then send 0, 1 or 2 and finish with 0x00. In diseqc switching 0xe1 is used as a repeat command rather than a "master first byte". I also see that while for a little while they set up the system to use diseqc frequency send, they end up setting it to do just the message envelope rather than 22 Khz tone. Does this look right or has anyone done some playing with that provider's boxes to know more about the format?

I know it's not diseqc but unsure of what it's called

[fn59]

I took a look at the patent for the multi-lnb for directv a while back. There was a mention of 22khz hi, and low for the ka band satellites at 99 and 103. But that's for newer receivers.
I think before the phase III lnb came into play to pick up 101, 110, 119 they used 3 seperate lnb's with a diseqc switch.

[Terryl]

I think DTV uses FSK* for it's SWM switches and transponder selection.

*FSK, Frequency Shift Keying, a data bit "0" equals one tone, a data bit "1" equals a second higher or lower frequency tone, it's a 22 Khz frequency, where the frequency is shifted up or down by the data.

Unlike the Diseqc commands that are tone bursts of different lengths, a data bit "0" is one long tone at 12.5 mS, or a data bit "1' is a 12.5 mS burst but pulsed on and off in 1 mS pulses.

[jvvh5897]

So, it seems no one really knows for sure. Since the drd430 was not on the recent obsolete list, and the menu in the drd430 shows three different dishes it likely is compatable with all but the newest (and I'm guessing it can't use the B-band method that uses frequencies from about 200 Mhz to 2150 GHz to have many LNBs signals all coming in at once).

I'm pretty sure it is not FSK--the 22KHz tone that the cx24110 can generate could be modulated that way, but not with the register settings I see in the code. It could be diseqc-like and that is what I pointed out in my 1st post--but with the register settings I see the 22KHz tone is not on--only the envelope is used and that is more like sending an IR remote command with the 38KHz modulation off as you see after the IR sensor receives the signal in the box.

[Terryl]

Take a look with a scope, I remember seeing the spec's somewhere, I can poke around the old library and see if I can find it.

[Terryl]

Ahhh, sorry I was wrong it's only for the SWM stuff running at 2.3 MHz, not the 22 Khz.


Sorry....My fault.

[fn59]

This might help/direct tv switching.jpg

[jvvh5897]

This might help/direct tv switching.jpg

No, that is no help either--I don'tneed to know how to hook up LNBs, I need to know the format that they use to do switching!

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Looking at a gaeboa schematic, I see that there to they use the diseqc out of the stv0299 chip and as that chip has fewer modes of operation than the drd430's cx24110 I can guess a little more. Must be diseqc format but with diff master 1st byte, so close out the thread.

[fn59]

The 4x4 switch is a 22khz switch, so 101w would be 22khz off, 119 22khz on.
The 110 satellite has only 3 tp's used by direct tv and I think the lnb had to be a specific type (bandstacked?), so I'm guessing the 110 tp's were converted to a higher frequency and also used 22khz on.