attempted to write invalid text to console

I have recently started to use my RepRap Ormerod 2 again after a couple of months of inactivity. I have not changed any settings, have not updated the firmware, and have even used the exact same gcode file as before. But I now frequently get the following error:

attempted to write invalid text to console
Resume-after-power-fail state saved
- Printing paused -
Heater fault
Warning: Tool 0 was not driven because its heater temperatures were not high enough or it has a heater fault
Printing paused

After the error, the printhead moves to 0,0, and the extruder temperature drops back down again.
The error usually comes at the exact time when the extruder temperature reaches the temperature set in the gcode, but sometimes it comes when a couple of layers have already been printed.

The gcode is stored on the memory card, and I control the printer and start the printing process through Pronterface. I first thought, there might have been some miscommunication with Pronterface, maybe bad usb cable, and so I tried disconnecting Pronterface directly after the print is started. That still resulted in the printhead moving to 0,0 and the extruder temperature dropping down. Of course, because Pronterface was disconnected, I could not see the error.

It is not clear whether the "attempt to write invalid text" causes the heater fault, or whether the heater fault causes some invalid text to be written. Despite the error, the heater seems to work fine, and the temperature sensor also seems to work fine.

Has anybody seen this error, and knows what could be the cause of it?

I have now discovered that when I set the extruder temperature by hand, that I get the same problem. When setting the extruder temperature to 240 degrees, it will heat up to approximately 222 degrees, and then it will give the error message:

attempted to write invalid text to console

this time without any other error messages. The target extruder temperature switches automatically to 0 after that, and the extruder cools down. So it is very likely that "invalid text" is the cause of the problem, and that it is triggered by the temperature almost reaching the target value.

Any help with this would be appreciated.

Edited 1 time(s). Last edit at 09/02/2019 11:29AM by Flyskyhy.

OK, after some digging around in the RepRapFirmware source code, I am pretty sure that what is happening is the following. The firmware is monitoring how fast the extruder is heating up, and decides that according to its heater model, it is not heating up fast enough. It then issues the error message "Heating fault on heater 1, temperature rising much more slowly than the expected XX °C/sec". The degrees symbol in that error message causes Pronterface to not show it, and issue the "attempted to write invalid text to console" instead.

The question is now, how to tell the firmware that it is OK that the temperature rises slowly?

Run heater tuning and save the results. [duet3d.dozuki.com]

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Ah, thanks. I did not know that was possible. It has been resolved now.