by educa » Tue Oct 09, 2012 2:31 pm
okay, my purpose it to have a chipkit do all the stuff...
I also have my own aproach to do PPI calculations. I used additions and let the counter overflow.
Anyway, there is still a lot of work to do.
My biggest problem is in acceleration ramping.
My lasercutter can run at 15mm/s from step 1 and for faster speeds it has to accelerate (at 6000 mm/s^²)
So as long as I cut at speeds UNDER 15mm/s everything is extremely easy to do. For most products 15mm/s is also allready very fast.
Speed ramping is easily possible with a precalculated table (the chipkit has a 32 bits 40MHz counter variable) but my only concern is that during that ramping I must be sure that my controller can get the gcode data fast enough. For example if you make a circle with 1000 lines, then this is a very smooth circle and you shouldn't break and reaccelerate for each line (1000 times) , but at top speed (which is 1000mm/s for me) that means that you must be able to provide your data very fast. Its all about the extreme conditions. Normal use isn't that problematic but I see that you made your ppi counter also able to go way faster then your steppers will ever go to be sure that won't be a limiting factor.