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dda.c: describe all lookahead cases in a comment.

This commit is contained in:
Markus Hitter 2013-11-29 19:31:13 +01:00
parent d10c0f3041
commit 1b5682c01a
1 changed files with 20 additions and 2 deletions
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22
dda.c
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@ -82,7 +82,24 @@ void dda_new_startpoint(void) {
It also pre-fills any data that the selected accleration algorithm needs, and can be pre-computed for the whole move.
This algorithm is probably the main limiting factor to print speed in terms of firmware limitations
*/
*
* Regarding lookahead, we can distinguish everything into these cases:
*
* 1. Standard movement. To be joined with the previous move.
* 2. Movement after a pause. This interrupts lookahead, and invalidates
* prev_dda and prev_distance.
* 3. Non-move, e.g. a wait for temp. This also interrupts lookahead and makes
* prev_dda and prev_distance invalid. There might be more such cases in the
* future, e.g. when heater or fan changes are queued up, too.
* 4. Nullmove due to no movement expected, e.g. a pure speed change. This
* shouldn't interrupt lookahead and be handled af if the change would come
* with the next movement.
* 5. Nullmove due to movement smaller than a single step. Shouldn't interrupt
* lookahead either, but this small distance should be added to the next
* movement.
* 6. Lookahead calculation too slow. This is handled in dda_join_moves()
* already.
*/
void dda_create(DDA *dda, TARGET *target) {
uint32_t steps, x_delta_um, y_delta_um, z_delta_um, e_delta_um;
uint32_t distance, c_limit, c_limit_calc;
@ -98,7 +115,8 @@ void dda_create(DDA *dda, TARGET *target) {
if (dda->waitfor_temp)
return;
// initialise DDA to a known state
// Initialise DDA to a known state. This also clears flags like
// dda->live, dda->done and dda->wait_for_temp.
dda->allflags = 0;
if (DEBUG_DDA && (debug_flags & DEBUG_DDA))