Z homming hangs the machine, after commit "Implement accurate acceleration profiles"

[casainho]

When I home the machine with G28 command, the Z homing hangs. If I revert this commit "Implement accurate acceleration profiles - 4bef47f" all works ok.

I started to wrote a message to dev group with subject "Issue on firmware -- Homing Z hanging":

I found that the Z homing sequence doesn't happen in totality. Here
is the current code:

static void zero_z(void)
{
// hit endstops, no acceleration- we don't care about skipped steps
SpecialMoveZ(startpoint.z - 250, config.homing_feedrate_z);
<-------------------- This works

synch_queue();

// move forward a bit
SpecialMoveZ(startpoint.z + 1, config.search_feedrate_z);
<-------------------- This works

// move back in to endstops slowly
SpecialMoveZ(startpoint.z - 6, config.search_feedrate_z);
<-------------------- This doesn't happen!!! Machine hangs.

synch_queue();

// this is our home point
//startpoint.Z = current_position.Z = config.home_pos_z *
config.steps_per_mm_z;
tTarget new_pos = startpoint;
new_pos.z = config.home_pos_z;
plan_set_current_position (&new_pos);

// move back in to endstops slowly
SpecialMoveZ(startpoint.z - 6, config.search_feedrate_z);
<-------------------- This doesn't happen!!! Machine hangs.

I found that this works, moving Z only in positive way. Maybe the
problem is a negative value of Z axis...

// move back in to endstops slowly
//SpecialMoveZ(startpoint.z - 6, config.search_feedrate_z);
SpecialMoveZ(startpoint.z + 6, config.search_feedrate_z);

[bobc]

There is nothing special about negative values, all coords are signed and moves are converted to a positive delta plus a direction. Also, the first negative move works?

I am wondering if there is some rounding issue that occurs with different config values. It could mean for a low feed rate the calculated rate ends up being zero, although there is supposed to be a minimum feed rate to stop that.

[bobc]

I changed my config file to the config_reprap_mendel one, and I hit the same problem. Printer hangs after second Z move.

X and Y homing seems to work ok though.

[casainho]

If you git revert your commit, the firmware will work well -- current stable firmware don't have your patch.

[bobc]

Yeah, I know that :) I am trying to find the bug and fix it!

[bobc]

The printer hangs after the second Z move, adding a synch_queue() prevents the hang. I need to look into this a bit further to see why the decel of the second move does not work correctly, just in case it could happen at other times.

[casainho]

Ok. I will test ASAP and I would like to release V1.0. Thanks!

[bobc]

That's funny, I seem to have accidentally reverted your last 2 commits, not
sure how that happened. Not sure how to fix it either...

On , casainho
reply@reply.github.com
wrote:

Ok. I will test ASAP and I would like to release V1.0. Thanks!

---

Reply to this email directly or view it on GitHub:

#3 (comment)

[bobc]

No wait, my bad. Your commits are there ok, for some reason it came through
as a branch merge.

I still don't quite understand git!

On , bobcousins42@googlemail.com wrote:

That's funny, I seem to have accidentally reverted your last 2 commits,
not sure how that happened. Not sure how to fix it either...

On , casainho
reply@reply.github.com>
wrote:

Ok. I will test ASAP and I would like to release V1.0. Thanks!

---

Reply to this email directly or view it on GitHub:

#3 (comment)

[casainho]

2011/12/28 Bob Cousins
reply@reply.github.com:

No wait, my bad. Your commits are there ok, for some reason it came through
as a branch merge.

I still don't quite understand git!

Branch merge?

Since I understand, a good way to work is you having your local master
equal to github master. You can locally create your branches were you
work... finally, merge them with local master. Finally commit and push
the changes you did in your master.

You can just keep your branches locally and private or uploaded them
to github so others can see them. Looks like Triffid Hunter did that.

[casainho]

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