I started today’s experimentation by loading the gpredict program. This was written by Alexandru Csete, at http://gpredict.oz9aec.net/
While his repository has all the source code, there is no reason to do anything other than load it into the pi, at least under the default Raspbian Debian Wheezy OS, by doing the following:
$sudo apt-get update
$sudo apt-get install gpredict
The first line makes sure the RPi has all the recent OS updates, and the second obtains the gpredict program and files. Once the files have been loaded, start x-windows and “run gpredict”.
I measured my RPi2 current when both the gpredict and xgps programs were running under X Windows (only 3% CPU utilization for both). It was right around 300 mA at with 5.3 volts at the input to the USB power cable. Hard to believe so much can be done for less than 2 watts of power. I don’t expect the LCD to add much more, but the servos will certainly add to the drain, especially the elevation control which has to fight gravity (probably a good reason to eventually balance the antenna even though the servo is capable of about 4x the required torque without balancing).
