[vdr] Re: [linux-dvb] OT: Diseqc Spec

[Holger Waechtler <holger@convergence.de>]

Lauri Tischler wrote:
> Holger Waechtler wrote:
>
> > Lauri Tischler wrote:
> >
> > > I've been trying to find specification for Diseqc 1.2,
> > > other then the one at www.eutelsat.com called 'position_app_note_v1.pdf'
> > > The initial spec from Feb. 1998.
> > > I have not been able to find anything newer.
> > > Specially I'm tring to find the spec for command 'Goto X',
> > > the original spec just says
> > > ---
> > > 3.10. Goto Angular Position (degrees)
> > > Command byte '6E' is not yet fully defined....
> > > ---
> > > Any pointers to working spec ?
> >
> >
> > http://www.eutelsat.com/satellites/4_5_5.html
> >
> > "Bus Specification" and "Update and Recommandations for 
> > Implementation" are the pdf's you are looking for, the other ones 
> > might be interesting too.
>
> Nope, they have even less information about command 'Goto X' then
> Positioner Application Note' document.
> Actually they have no information at all about bits and nibbles of
> 'Goto X' command.
are you sure it's actually used anywhere? the DiSEqC spec is ermmh - 
let's say somewhat fuzzy about some thing, I could well imagine that 
they never finished specifying this command...

anyway - that's what I found:

http://www.eutelsat.com/satellites/pdf/Diseqc/associated%20docs/position_app_note_v1.pdf
(page 11)

"The high nibble of the first data byte indicates how the remainder of 
the angular data is to be interpreted. The values  F ,  0  and  1  are 
allocated to support full rotation in a horizontal plane (e.g. for 
terrestrial sources). The nibble  0  references the angle defined in the 
remainder of the data to North (0°),  1  adds 256° clockwise to the 
angle and  F  subtracts 256°. The low nibble of the first data byte 
indicates the clockwise rotation angle in increments of 16°. Thus a 
first data byte of  00  defines due North,  01  defines an azimuth of 
16° East,  0A  (hexadecimal) an azimuth of 160°, and  10  (hexadecimal) 
a rotation of 256° clockwise from north. The high nibble of the second 
data byte defines the angle in degrees, and the low nibble indicates the 
fractional part of a degree, if required. Note that the low nibble is a 
true binary fraction, and is not Binary Coded Decimal. Thus the most 
significant bit (of the low nibble) defines half a degree, the next bit 
a quarter degree and the least significant bit a sixteenth. If the 
Tuner-receiver User-interface is to show a decimal value, then the ten 
closest fractional values can be employed, as given in the following table."

hope that helps - but I fear you've seen it before,

Holger



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