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RE: Programming question - dish angle



Phil:

Read up on CORDIC angle computations.  All
rotations done using only +/-'s.  Tailor
made for this.  However, I think your
job might be easily done by a table lookup
if you can store a large enough table lookup.
I take it you can not do multiply's?  If so,
then you could use a smaller table and do
linear or cubic spline interpolation.

Bob
N4HY


-----Original Message-----
From: owner-AMSAT-BB@AMSAT.Org [mailto:owner-AMSAT-BB@AMSAT.Org]On
Behalf Of Phil
Sent: Tuesday, October 07, 2003 6:51 AM
To: amsat-bb@AMSAT.Org
Subject: [amsat-bb] Programming question - dish angle


Hello everyone,

I'm looking for ideas. I have some code that counts the azimuth and
elevation
pulses from my dish rotator and then displays the positions on a 2 line 16
character LCD display.

There is a direct correlation between counted pulses for azimuth position
but
not for elevation. I apply the cos rule to get the dish angle based on the
length of the actuator arm. So far so good.

It seems like a good idea to have a PIC take over the roles of pulse
counting
and display because the CPU is already pretty busy with Doppler correction
calculations and uplink aerial positioning, plus other Amateur Radio related
tasks. However, I can't think of any way to calculate the elevation angle
using the PIC's instruction set.

How do pulse counting controllers usually accomplish this feat? Look-up
tables
maybe?

--
Regards,
Phil.


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