Proportional (P), Integral (I), Derivative (D). These are the main terms that describe how the servo loop operates. They have everything to do with how a servo system operates. Galil lets you "tune" these values with KP, KI, and KD commands. OF is the Galil voltage offset command. OF0 will be 0 volts offset while OF9 will be 9 volts offset. And anything in between. This is command that we use on the Galil to basically use the axis as an analog output. But... KP, KI, and KD need to be set to 0, otherwise they may change the base voltage of the output!
The Galil is a very complex and flexible motion controller. A good bit of knowledge about Galil controllers is pretty much a prerequisite to using one with Mach effectively. We cannot possibly put all of that into the plugin docs. If you know how to operate a Galil outside of the Mach environment, then setting up the plugin via the plugin docs is pretty straight forward. However, if you don't have a good handle on the Galils, it can be challenging (to say the least).
The good news is that the Galil documentation is pretty good. And they have a nice forum on their website with lots of answers. Also, the application notes are an invaluable resource when it comes to connecting the Galils and wiring up ICMs.
There are 3 things that anyone needs to know a good deal about when using the Mach/Galil combination:
1. Servo theory and operation. This means getting to know your servo/drive combination pretty well too, as they are all a little bit different.
2. General Galil concepts and operation. This includes wiring the ICMs up to the servo drive, inputting the servo tuning parameters,and BN (burning) them to the Galil's NVRAM. Making the servos move with only the Galil terminal is a good first step.
3. Mach. Mach started off life as a system that drove stepper drives from the parallel port. This paradigm is most noticeable in the "Ports and Pins" configuration dialog. Later on, the concept of external motion controllers came to life. But these external motion controllers pretty much don't resemble a parallel port at all. So there has always been this sort of square peg/round hole type thing going on. So the way we implement an external controller is by providing "virtual ports and pins" via the plugin. That is why we have a pin map in the Galil plugin documentation. So you just installed Mach and have fired it up, right? Is all of this immediately apparent? Unfortunately, No.
None of this comes fast and easy. I can't tell you how many nights, days, and weekends I have spent pouring over the Mach and Galil docs. And I'm still learning every day!
But it is all worth it. The Mach/Galil combination is poetry in motion.
Steve