> There is a bug in DvbStream::gotoX in Kaffeine 0.8.8, which is fixed by
> the
> attached patch.
>
> Look for example at what happens when azimuth = 15.951. The motor should
> be
> driven to 16.0 degrees, but when 15.951 is rounded up with if (USALS>0.5)
> ++rd; the carries into the upper nibble of CMD2 and the lower nibble of
> CMD1 are not handled properly. The result is CMD1 represents 0 instead of
> 16
> degrees and CMD2 is undefined, being set by the non-existent 11th element
> of
> DecimalLookup.
>
> The patch fixes it, and I also took the opportunity to fix the strange
> division by while loops.
>
> Regards,
> Hans
-------- Original-Nachricht --------
> Datum: Tue, 14 Jul 2009 16:17:30 +0200
> Von: "Jesko Schwarzer" <jesko.schwarzer@xxxxxxxxxxxxxxxx>
> An: "\'Hans Werner\'" <HWerner4@xxxxxx>, linux-media@xxxxxxxxxxxxxxx
> Betreff: AW: [BUG][PATCH] kaffeine 0.8.8 USALS/GotoX problem
> Hello Hans,
>
> I looked into the patch - just to be informed what's going on and got
> confused by such code.
> I reimplemented it to test it against side effects and still do not
> understand why it is written so complicated. Sure, I don't know the
> environment of the code, but does it matter in this case ?
>
> If you like try these few lines (the last 3 lines) as a replacement:
>
> unsigned long USALS;
> int CMD1;
> int CMD2;
>
> if ( azimuth>0.0 )
> CMD1 = 0xE0; // East
> else
> CMD1 = 0xD0; // West
>
> /*-----------------------------------------------*/
> USALS = ( fabs( azimuth ) * 16.0 + 0.5 );
> CMD1 |= ( USALS & 0xf00 ) >> 8;
> CMD2 = ( USALS & 0x0ff );
> /*-----------------------------------------------*/
>
> Regards
> /Jesko
Hi Jesko,
thanks for looking at it. I see the main difference in your
version is that there is no DecimalLookup for the bottom 4 bits.
I took a look at the Eutelsat specs here:
http://www.eutelsat.com/satellites/pdf/Diseqc/associated%20docs/positioner_appli_notice.pdf
The relevant section is 3.10.
Reading that I see that the lower four bits should never have
been coded with DecimalLookup at all !! The 12-bit value should be
a true binary fraction (not any coded form of decimal) representing
the angle to a precision of 1/16th of a degree.
Whoever originally wrote the routine may have misinterpreted Table 2
which shows a lookup table converting the lower 4 bits of CMD2 to
decimal, just for people who want to make STB displays and data entry
limited to just 0.1 degree accuracy.
So I think your version of the routine is correct. Mine differs
sometimes by 1/16th of a degree (not perceptible with my equipment),
and is the same otherwise.
I have attached a new version of the patch. I compiled and tested
with my rotor and confirmed it works.
Regards,
Hans
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--- dvbstream.cpp.orig
+++ dvbstream.cpp
@@ -758,31 +758,20 @@
void DvbStream::gotoX( double azimuth )
{
- double USALS=0.0;
+ unsigned long USALS;
int CMD1=0x00, CMD2=0x00;
- int DecimalLookup[10] = { 0x00, 0x02, 0x03, 0x05, 0x06, 0x08, 0x0A, 0x0B, 0x0D, 0x0E };
+ //rotation direction
if ( azimuth>0.0 )
CMD1 = 0xE0; // East
else
CMD1 = 0xD0; // West
- USALS = fabs( azimuth );
-
- while (USALS > 16) {
- CMD1++;
- USALS-= 16;
- }
- while (USALS >= 1.0) {
- CMD2+=0x10;
- USALS--;
- }
- USALS*= 10.0;
- int rd = (int)USALS;
- USALS-= rd;
- if ( USALS>0.5 )
- ++rd;
- CMD2+= DecimalLookup[rd];
+ //angle : 12 bits with a precision of 1/16th of a degree
+ //a true binary fraction, NOT binary coded decimal
+ USALS = ( fabs(azimuth)*16 + 0.5 );
+ CMD1 |= (USALS & 0xf00) >> 8;
+ CMD2 = (USALS & 0x0ff);
rotorCommand( 12, CMD1, CMD2 );
}
