Firmare borked mid print :/

Hi,

DISCLAIMER: I'm posting this only to share my experience and get some pointers on how this could have happened, not to report a bug.

I suddenly had my extruder motor going crazy half trough printing this thing: [www.thingiverse.com]
The symptoms were really weird the extruder stepper motor was skipping steps and vibrating at all attempts to extrude when printing, but when I was extruding manually from the manual control in the host things were great.

The first things on my mind was that there was a mechanical problem with the extruder assembly, the hotend itself or that the motor driver was busted. So I took everything apart.

The hotend was fine, all clean, thermistor good.
The extruder was fine, the hobbed bolt needed cleaning so I cleaned it.
I have replaced the presumed faulty driver, same problems as before.

Then I noticed that the extruder motor acted as it would do when you would try to turn it way to fast loosing all torque, or as when the stepping sequence was wrong.

Since the stepping sequence is handled by the driver it could only be something wrong with the step command the driver got.

In the end I removed all other possible causes (noise, bad connections etc) and came to the conclusion that something must have gone wild with the firmware.

I have reflashed the firmware and all got back to normal.

I can only assume that at some point something of the below happened:

- the EEPROM got corrupted - maybe during testing saving settings trough the host
- the flash got corrupted - and the portion of the code handling the extruder stepping got messed up

AFAIK Memory corruption can occur on Atmel MCU's in brownout situations and it happened to me before, how ever I cannot quite link this to the current setup.

It's no EEPROM corruption if it happens half way. The EEPROM is only read at the start or if you change them, which you shouldn't do during printing.

RAM corruption would need instable voltage, but could happen.

The big question is what you did when it happened. Did you reset the board or just kill the job. You said manual extrude was possible, but was it after a restart, which reinitialized everything or even after cleaning the hot-end (if you have backflow of hot filament it may block - can happen with man retracts in a short period, pla too hot,...)?

I mean, perhaps your g-code produced a state that causes a problem. But after printing so far, you normally have had every code used before sucessfully, but you never know.
If you get the same problem at the same position it is the code in combination with a second reason. You may test this without filament (set min. extruder temp. to 0, print with 30° or so). If you succeed, it was a undefined hardware error (ram, blocking). If the same fails with real filament you could think of blocking, higher torque needed.

Just a few thoughts to start.

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It happened during print, I was only watching it printing.

After it happened I killed the job to stop it. I have reset the board, I have disconnected power.

After I powered it up again, I could move the axis-es without issues, I could extrude with a speed up to about 800 mm/min if I would hit the extrude button in the host. At this speed it sometimes lost steps. Before this happened (and after I have reflashed) I never had any issues with the extruder speed, it's a pretty beefy motor.

In the state it was whatever print I have tried regardless of speed settings, the extruder went wild at any attempt to extrude from the gcode.

I did suspect a jam in the hotend or some other mechanical issue but there was none to find, after I had the hotend back together I still had the exact same behavior.

It only was fixed with erasing and reflashing ... weird I know so I thought I should share.

I didn't get that reprogramming fixed the problem. Really strange error. But good to know if it happens to me .

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Repetier-Software - the home of Repetier-Host (Windows, Linux and Mac OS X) and Repetier-Firmware.
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Are you sure it fixed the problem? Did you run the same gcode file again and it worked ok?

I've seen similar behavior when my firmware thinks my extruder needs to move a lot faster than my x/y axes, for example. Like the extruder is in "absolute" coordinates mode, but the gcode is using "relative", so you send a "G1 E0" -- meaning, "don't extrude" -- but the extruder thinks it has to rewind all the way back from 489.45 to zero. If you don't have a reasonable maximum speed in your firmware, it can cause it to overdrive the steppers and cause the crazy behavior you're seeing.

Plus, I've heard Traumflug found some units that had EEPROM (Codespace memory) corruption caused by brownouts. Setting the brownout-reset fuse should guard against this.

I guess this is the Repetier Firmware you saw this on?

Phil

Yup reflashing fixed it definitely I printed the same gcode twice after with different layer heights with no problems.