Hi there,

does anyone have an idea how to edit the firmware?
Might the board be Arduino-based, so that I could use the Arduino-software to download the configuration from the board, edit it and upload the changed version?
I ordered a heated bed for my startt, since the board does seem to support it, but it seems to be disabled in firmware.
At least, when I connect the printer to repetier, the options for controlling the heatbed disappear.

I would like to change that, but do not want to brick the electronics.

I played around with a RAMPS-board for another project, so I have a little experience in Arduino.

Hi Tomi,

Thanks for the hint about Skynet, I will have a look into that.

Actually I have not fixed the heatbed yet.

I think the easiest way would be just to drill some extra holes into the top acrylic plate so that the screws of the four edges of the heatbed fit into those.

I would insulate the bottom of the heatbed with some silica wool so that the acrylic does not get too warm and warp.
That method would cost some z-height though.

A better way would be to replace the lower plate (the one those linear guide blocks are attached to) and fix the heatbed directly to that, so that the four screws of the heatbed are used for leveling with the springs in between.
Lasering that piece would be a fine solution.

@Antonio,

thanks for that link, that would definitely be helpful.
I polished up my Arduino experience in the meanwhile.
It is not possible do download the configuration file from the board, as an Arduino program is compiled before it is uploaded to it.
Some info can be imported from the EEPROM though, like steps per mm for the steppers.
But I am more concerned about stuff like the display settings. It took me ages to get those right on an RAMPS board, without those, the display might stay blank.
Also, you would have to find out other stuff, for example what kind of thermistor is used.

Since I would like to stay everything as it is and just want to activate the heatbed option, having the configuration.h file would be very helpful.

I sent a support request to imakr this evening and asked for it and got this reply within an hour:

Hi,

 Thank you and we are glad you are happy with the Startt printer. We are currently talking to our manufacturer about the firmware and once we get it I will post it on the forum. 

Kind regards,

Jack

iMakr Support Team


So since I am away for a few days now anyway, I think I will wait if something comes up in the forum.
Just uploading some sort of firmware I cobbled together by myself is to risky for me because I am afraid I could mess up the display or something.

Hi Tim, hi Romeo,

thanks for sharing your experiences.

@Romeo, Tim has the right EEPROM settings for motor-steps, in the picture you see what I get when I read out my original EEPROM-settings from the Startt with Repetier. From Repetier, you can also export that settings into a file for backup. I did that, find it attached.



@Tim: Did you use the current version of the Arduino IDE (1.8.3) or did you have to install the old version (1.0.5) that is described in the Github Repository? If yes, do you know if it is possible to have both installed on your PC at the same time?



Thanks in advance :)

And another question. In the repetier firmware, there is an option to control the extruder fan (the one that currently starts to run as soon as the printer is connected to power).




Does anyone know, if on this version of the Melzi board, this fan can be controlled by firmware or is just hardwired to 12V?
When I look at the board with my limited electronic skills, I would believe it is possible. Next to the two plugs for the two fans are two identical capacitor-transitor-thingy-areas, so might those be for controlling the two fans?
The Reprap-page describing the Melzi board does not seem to have the latest version with the extra socket for the extruder fan:
http://reprap.org/wiki/Melzi#Melzi_Version_2.0

I would like the option that the extruder fan only runs when hotend temperature is for example above 50°, so that the printer is completely quiet when powered up but not in action.

So, after playing around with my heated bed and firmware,

has anyone successfully installed and activated a heated bed yet?

Here is where I stand now and which problem I still have:

I successfully changed and flashed Repetier firmware onto the Melzi board.
I used the configuration.h Tim uploaded here with a slight modification (changed temperature sensor type for the heated bed).

I have mechanically installed a heated bed (Mk2b 120mm x 120mm) on my Startt.
Connected to a constant 12V-power supply, it heats up quite quickly and draws about 3A of current.
That is roughly the same current as the extruder heater cartridge draws, so it should be no problem for the heatbed-MOSFET on the board.

So now, with updated firmware, in repetier host, when I connect it to the printer, the heatbed option does not disappear and the correct heatbed temperature is shown on the printer display as well as in Repetier.
Also it changes when I heat up the bed externally, for example by laying my hand on the bed for a few seconds.

When I activate the heatbed, the printer-display changes from 0% to 100% heating power for the bed, in the same way it does when I activate the extruder heating, the same shows in Repetier Host.

Extruder heating at 100%:



Heated bed heating at 100%:



Here is a screenshot from RH. At 1., I switched on the heatbed, at 2. the extruder heater.
As you can see, the hotend really heats up, the bed does not:



When I measure the voltage at the heatbed-terminal on the board, there is none, I get 0V when it should be 12V.
As said before, the bed itself works perfectly when connected to an external 12V-power supply.

I checked the firmware files for entries that might have to do with this.

In configuration.h, the board type is set to #63, which in pins.h corresponds to the Melzi:

excerpt from configuration.h:

#define NUM_EXTRUDER 1
#define MOTHERBOARD 63
#include "pins.h"

#define HAVE_HEATED_BED 1
#define HEATED_BED_MAX_TEMP 110
#define SKIP_M190_IF_WITHIN 3
#define HEATED_BED_SENSOR_TYPE 1
#define HEATED_BED_SENSOR_PIN TEMP_1_PIN
#define HEATED_BED_HEATER_PIN HEATER_1_PIN
#define HEATED_BED_SET_INTERVAL 5000
#define HEATED_BED_HEAT_MANAGER 1
#define HEATED_BED_PID_INTEGRAL_DRIVE_MAX 255
#define HEATED_BED_PID_INTEGRAL_DRIVE_MIN 80
#define HEATED_BED_PID_PGAIN_OR_DEAD_TIME 196
#define HEATED_BED_PID_IGAIN 33
#define HEATED_BED_PID_DGAIN 290
#define HEATED_BED_PID_MAX 255
#define HEATED_BED_DECOUPLE_TEST_PERIOD 300000
#define MIN_EXTRUDER_TEMP 150
#define MAXTEMP 260
#define MIN_DEFECT_TEMPERATURE -10
#define MAX_DEFECT_TEMPERATURE 290




excerpt from pins.h:

/****************************************************************************************
* Melzi pin assignment
*
****************************************************************************************/
#if MOTHERBOARD == 63
#define KNOWN_BOARD 1
#
...
// (extruder)
#define HEATER_0_PIN 13
#define HEATER_2_PIN -1
// bed (change to 12 for breakout pin on header)
#define HEATER_1_PIN 10

As I have read in another forum, Pin10 should be correct for the Melzi, so I have run out of ideas right now.

Hints, anyone?