PBP projects for R/C models

[ScaleRobotics]

Great job Ken. What you are doing is the best way to learn about the interrupts. You have to play with them. That is a great start.

I believe both pulsin and pulsout are blocking commands. While they run, nothing else can happen on your chip. Once they are finished, sure, things resume and the program takes over. For a single servo, this is fine. But once you start throwing in sonar, multiple servos, other things you have thought of, and some you haven't thought of yet ... then you start to run out of time to do all these things using blocking commands. Especially if you want to go 20 mph.

As it stands, 20mph is half a foot for each 20ms (that is every chance you get to make an R/C correction). For your sonar, it takes a bit over 20ms, so if that is the only input, the best your chip can do is determine a correction every other 20 ms, or every foot.

In fact, just listening to the echo pulse on your sonar takes up to 25 ms, so that alone screws up everything if we use blocking commands like pulsin. (and double the screwed if you are listening to two of these!)

So, in the long run I think it is best to use interrupts for listening to your sonars, as well as outputting to your servo's. I can't remember how you are switching your transmitter for R/C control vs pic control, but that too might as well go on interrupts.

If you do, you have all kinds of time. You can be listening for two sonars at the same time, chewing on some math to determine the amount of turn, etc. If you want speed, it is most definitely the way to go.

That said, exactly what you are currently doing to learn is what I would recommend. Use the commands you know with interrupts to make things happen, and see how they work, and how to adjust them. Later on, when you feel comfortable with them, try adding in another interrupt timer to control a servo pulse.

[cncmachineguy]

Hi Walter, I love what you are saying about using int instead of pulsein/out. I am having trouble visualizing how to do that.

In my head, something has to be the overall clock, thats where my suggestion of 5msec came from. when I think about what you are saying, all I seem to be able to see is all these events started waiting for an int to make them stop. so I see like 6 different timers going all at once.

Or maybe you have 1 timer going for the 20ms, then do everything else sequencially using a different timer.

EDIT: The slow sonars are gonna definitly limit the top speed! Maybe as an upgrade once it works slowly, infra red emitters and detectors. This way they could also be used at the same time by sending different signals on each.