Add dedicated pen up/down button?

[Jeff Thompson]

I love my Axidraw – thank you again for making such a rad piece of hardware!

One thing that would be really handy, though, is a dedicated button on the machine that would toggle the pen up and down. (My computer is often kind of far from the machine, making setup a lot of back-and-forth.)

Would it be possible to mod the firmware and solder a button somewhere to the control board?

[Windell Oskay]

You could potentially modify the firmware to to this.

But, can I ask what the purpose of this change would be? What is it that you’re doing that requires you to toggle the pen up and down repeatedly?

[Jeff Thompson]

I’ve noticed that I often want to adjust the pen position: to replace the paper, to adjust the pen itself, add/remove weights (which I find very helpful with certain drawing implements), etc. Basically, I find I use the pen up/down and motors off to re-Z a lot, making a hard-wired button helpful. My studio is set up in such a way that my Axidraw isn’t very close, so I have to go back and forth. By no means a must-have but seemed like a useful mod.

[Windell Oskay]

Once the pen is in the pen-up position (which you can set from your computer before starting the session), there should not be any need to manually lower or raise the pen again while setting up different pens and papers, even during a full day of use. So, I’m not sure exactly what it is that you’re doing.

It is possible to hard code something like this into custom firmware if that’s your preferred way of coding. But, it is also something that could be done with a custom Inkscape extension, a modification to one of ours, or an independent script on the computer — without any changes to the firmware.

[Jeff Thompson]

Thanks – not sure I understand re pen though. If I put a different pen in the machine I need to raise/lower the pen motor to set the pen’s position in the holder. (I have 3D printed some pen holders and stop-collars for just this purpose, which makes swapping pens faster.) I know this is maybe a boutique addition, but at least in my use would make the workflow faster.

I looked on Github but don’t see the firmware source code – is it open source? I don’t suppose it already polls unused pins on the board, meaning I could just mod the Inkscape extension? I could stick an Arduino Mini or something in there to read the button, but was hoping for a cleaner solution.

[Windell Oskay]

What are you doing when inserting a pen that requires you to lower it?

(We have occasionally seen people insert a pen in the “pen down” position, and then manually change the pen-down setting, but that’s the opposite of the recommended procedure.)

The EBB firmware is open source, and hosted in the EggBot repository: https://github.com/evil-mad/EggBot/tree/master/EBB_firmware

The other I/O pins above the servo connector are not polled by default, but you can poll them through software, for example by modding an extension. We would always recommend to use the existing interface rather than modifying the firmware, especially for things like this that are easily done through software: http://evil-mad.github.io/EggBot/ebb.html

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