Pull Request #1 broke delta/motion-ctl calcs (XYZ_STEPS=~2666.67, should be ~83)

[FlyingLotus1983]

Initially seen by Douglas last week, confirmed by me yesterday night. Causes the machine to move too many steps, causing errors and other bad things. Backing out the change results in normal movements, but doesn't fix the scaling issue that pull request #1 set out to fix.

[FlyingLotus1983]

Suggested change by Douglas Pearless, via dev-group mailing list, 2/1/2015:

Hi Team,

I have ported part of the code to run under Xcode on my mac and I can confirm the results:

// default settings
#define BELT_THICKNESS 1.49  // thickest part of belt
#define TOOTH_DEPTH 0.74     // thinnest part of the belt
#define TOOTH_SPACING 2.0   // 2mm for GT2 belts

// recalculate circumference to take into account tooth thickness, as this adds to the radius of the pulley
#define BIG_PULLEY_CIRCUM BIG_PULLEY_TEETH*TOOTH_SPACING + (BELT_THICKNESS - TOOTH_DEPTH)*6.283185
#define SMALL_PULLEY_CIRCUM SMALL_PULLEY_TEETH * TOOTH_SPACING

#define XYZ_FULL_STEPS_PER_ROTATION 200.0
#define XYZ_MICROSTEPS 16.0
#define SMALL_PULLEY_TEETH 16.0
#define BIG_PULLEY_TEETH 150.0
//#define PULLEY_REDUCTION BIG_PULLEY_TEETH/SMALL_PULLEY_TEETH
#define PULLEY_REDUCTION BIG_PULLEY_CIRCUM/SMALL_PULLEY_CIRCUM
#define xstr(s) str(s)
#define str(s) #s
#define XYZ_STEPS (XYZ_FULL_STEPS_PER_ROTATION*XYZ_MICROSTEPS*PULLEY_REDUCTION)/360.0

#include <iostream>

int main(int argc, const char * argv[]) {
    // insert code here...
    //std::cout << "Hello, World!\n";
    float result = XYZ_STEPS;
    printf ("result %F", result);
    return 0;
}

result 2666.668213

Program ended with exit code: 0

The issue is two fold:
(1) the order of mathematical precedence in the line that calculates the BIG_PULLEY_CIRCUM
(2) the small pulley circumference calculation is missing the 2xPI (the *6.283185 )

I have highlighted the changes in pink

// default settings
#define BELT_THICKNESS 1.49  // thickest part of belt
#define TOOTH_DEPTH 0.74     // thinnest part of the belt
#define TOOTH_SPACING 2.0   // 2mm for GT2 belts

// recalculate circumference to take into account tooth thickness, as this adds to the radius of the pulley
#define BIG_PULLEY_CIRCUM (BIG_PULLEY_TEETH*TOOTH_SPACING + (BELT_THICKNESS - TOOTH_DEPTH))*6.283185
#define SMALL_PULLEY_CIRCUM SMALL_PULLEY_TEETH * TOOTH_SPACING *6.283185

#define XYZ_FULL_STEPS_PER_ROTATION 200.0
#define XYZ_MICROSTEPS 16.0
#define SMALL_PULLEY_TEETH 16.0
#define BIG_PULLEY_TEETH 150.0
#define PULLEY_REDUCTION BIG_PULLEY_TEETH/SMALL_PULLEY_TEETH
#define xstr(s) str(s)
#define str(s) #s
#define XYZ_STEPS (XYZ_FULL_STEPS_PER_ROTATION*XYZ_MICROSTEPS*PULLEY_REDUCTION)/360.0

#include <iostream>

int main(int argc, const char * argv[]) {
    // insert code here...
    //std::cout << "Hello, World!\n";
    float result = XYZ_STEPS;
    printf ("result %F", result);
    return 0;
}

result 83.333336

Program ended with exit code: 0

So that explains why we had the issue :-)

Therefore, either changing the two lines as I did, or Neil’s solution will work.

Cheers

Douglas

[AlessioMorale]

this is still wrong:

#define BIG_PULLEY_CIRCUM (BIG_PULLEY_TEETH*TOOTH_SPACING + (BELT_THICKNESS - TOOTH_DEPTH))*6.283185
#define SMALL_PULLEY_CIRCUM SMALL_PULLEY_TEETH * TOOTH_SPACING *6.283185

it should really be:

#define BIG_PULLEY_CIRCUM (BIG_PULLEY_TEETH*TOOTH_SPACING + (BELT_THICKNESS - TOOTH_DEPTH) * 6.283185)
#define SMALL_PULLEY_CIRCUM SMALL_PULLEY_TEETH * TOOTH_SPACING