The best way to learn programming is to read code. All of the standard code for components lives on git here
github.com/LinuxCNC/linuxcnc/tree/master/src/hal/components
Pick one of the simple components like or2 or and2 that you use and understand, then review the source for it.
The idea behind hal is that each component is stand alone iits own compartment so if it fails, everything else still works. So the only way to use another pin such as halui.program-on is to create a new in pin of the same data type and use a hal net statement to connect it to the in pin.
There are also many ways to skin a cat in C. Grotius used a hal variable called period to count milliseconds and convert it to seconds for your timer. There is another
implicit varuable
called fperiod which counts in seconds so I would probably do it like this because we are already using floating point numbers.
Code:
// Timer
totalnsec += fperiod;
where using += is shorthand for totalnsec = totalnsec + fperiod;
Its cleaner and easier to read.
floating point numbers are much bigger and take more processing overhead to work with so we only use them when we have to but that is probably a hangover from an earlier era where PC's did not have the grunt they do today. But think of that if you are working with an arduino.
