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dda.c: remember steps per m of the fast axis for rampup calculation. 

For now this is for the initial rampup calculation, only, notably
for moving the Z axis (which else gets far to few rampup steps on
a typical mendel-like printer).

The used macro was verified with this test code (in mendel.c):

[...]
int main (void) {
  init();

  uint32_t speed, spm;
  char string[128];
  for (spm = 2000; spm < 4099000; spm <<= 1) {
    for (speed = 11; speed < 65536; speed *= 8) {
      sersendf_P(PSTR("spm = %lu  speed %lu ==> macro %lu  "),
                 spm, speed, ACCELERATE_RAMP_LEN_SPM(speed, spm));
      delay_ms(10);
      sprintf(string, "double %f\n",
              (double)speed * (double)speed / ((double)7200000 * (double)ACCELERATION / (double)spm));
      serial_writestr((uint8_t *)string);
      delay_ms(10);
    }
  }
[...]

Note: to link the test code, this linker flag is required to add
      the full printf library (which does print doubles):

  LDFLAGS += -Wl,-u,vfprintf -lprintf_flt -lm
This commit is contained in:
Markus Hitter 2013-12-06 01:11:59 +01:00
parent 3da2363ac5
commit 9739382da9
3 changed files with 14 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
dda.c
View File

@ -187,17 +187,21 @@ void dda_create(DDA *dda, TARGET *target) {
dda->total_steps = dda->x_delta;
dda->fast_um = x_delta_um;
dda->fast_spm = STEPS_PER_M_X;
if (dda->y_delta > dda->total_steps) {
dda->total_steps = dda->y_delta;
dda->fast_um = y_delta_um;
dda->fast_spm = STEPS_PER_M_Y;
}
if (dda->z_delta > dda->total_steps) {
dda->total_steps = dda->z_delta;
dda->fast_um = z_delta_um;
dda->fast_spm = STEPS_PER_M_Z;
}
if (dda->e_delta > dda->total_steps) {
dda->total_steps = dda->e_delta;
dda->fast_um = e_delta_um;
dda->fast_spm = STEPS_PER_M_E;
}
if (DEBUG_DDA && (debug_flags & DEBUG_DDA))
@ -356,7 +360,8 @@ void dda_create(DDA *dda, TARGET *target) {
// Acceleration ramps are based on the fast axis, not the combined speed.
dda->rampup_steps =
ACCELERATE_RAMP_LEN(muldiv(dda->fast_um, dda->endpoint.F, distance));
ACCELERATE_RAMP_LEN_SPM(muldiv(dda->fast_um, dda->endpoint.F, distance),
dda->fast_spm);
if (dda->rampup_steps > dda->total_steps / 2)
dda->rampup_steps = dda->total_steps / 2;

1
dda.h
View File

@ -128,6 +128,7 @@ typedef struct {
uint32_t total_steps; ///< steps of the "fast" axis
uint32_t fast_um; ///< movement length of this fast axis
uint32_t fast_spm; ///< steps per meter of the fast axis
uint32_t c; ///< time until next step, 24.8 fixed point

8
dda_maths.h
View File

@ -68,7 +68,13 @@ const uint8_t msbloc (uint32_t v);
// s = 1/2 * a * t^2, v = a * t ==> s = v^2 / (2 * a)
// 7200000 = 60 * 60 * 1000 * 2 (mm/min -> mm/s, steps/m -> steps/mm, factor 2)
// Note: the floating point bit is optimized away during compilation.
// Note: this macro has shown to be accurate between 10 and 10'000 mm/s2 and
// 2000 to 4096000 steps/m (and higher). The numbers are a few percent
// too high at very low acceleration. Test code see commit message.
#define ACCELERATE_RAMP_LEN_SPM(speed, spm) \
(((speed) * (speed)) / \
(uint32_t)((7200000UL * ACCELERATION) / (spm)))
// For X axis only, should become obsolete:
#define ACCELERATE_RAMP_LEN(speed) (((speed)*(speed)) / (uint32_t)((7200000.0f * ACCELERATION) / (float)STEPS_PER_M_X))
// Initialization constant for the ramping algorithm.