Cricut Mini

[David Mitchell]

So, just for curiosity's sake, I bought a broken Cricut Mini off eBay to take apart and examine for differences, as well as to get one of the often-broken carriage "arms" as a model for replication.

I'll post a proper wiki page with photos, but here's the TL;DR:

The entire thing is different, top to bottom. Different width (handles 8.5x11"), different case, different internals, different carriage, everything.

The processor is now a PIC (used to be AVR 128 or 1281 depending on model). I'd be willing to bet the Expression 2 does as well.

The motherboard is about 1/4 the size of the old one, about 2"x5".

Both steppers now use encoder wheels, I didn't see the X-endstop button anymore, but it might have just been moved and miniaturized or something.

No more keyboard, no more OLED display, no size, pressure, or speed knobs. Just a power button and a load/unload button.

The cutter carriage design now uses a standard "pull" solenoid mounted on the side of the machine, so the carriage no longer has any electronics on it all, it slides side to side and pivots up and down when the solenoid turns a bar.

Disassembly is a bit easier now, no more plastic latches, just screws.

Uses the same blade holder and cartridges, but you have to cut using the Cricut Craft Room software on the computer or a Gypsy device, which still prevent you from cutting images of your own design (you have to purchase all art via cartridges or the Craft Room website).

No idea if you can still re-flash the firmware via the cartridge port. I haven't actually tried to see if it actually cuts, but it did start up and seemed to do the load/eject cycle OK.I also have not tried to see if the last Cricut-compatible version of Make-the-Cut will work with it. I give it 50/50 odds.

regards
David

[Amishacker]

That wasn't too long!

Thanks for the review David, and keep hackin'

I was thinking about getting a cricut for Anne - if you can escape the Craft Room lock-in for this'n it would be perfect.

When you get a sense of how it runs, can you include in your guide the thicknest card stock it will cut and how that compares to the originals?

[Paul Bonser]

Seems like since you control it via the computer, it should be feasible to figure out the protocol.

It'd be interesting to do some USB sniffing to see if the protocol could be figured out. Will their software run on WinXP? All the USB sniffing software I've found so far doesn't work on anything newer than that.

David

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[Joe Cline]

I wanted a Cricut until I started looking at buying the cutting patterns.
There was a compay that and broke the cricut encoding and made cutting designs not on cartridges work. Cricut sued them out of existence. :( so no Cricut for me.
http://www.scrapbookupdate.com/2011/03/11/provo-craft-sues-sure-cuts-a-lot-alleging-copyright-violations/

Joe Cline
REALTOR, Broker
Affinity Properties, Inc.
512.415.9614 cell
joec...@gmail.com
http://www.AffinityProperties.com

[David Mitchell]

Yeah.. Sorry Paul, the cutting protocol is encrypted. Although I know where to find the keys, I'm not going there. Make the Cut and Sure-Cuts-A-Lot were both sued into removing Cricut support. Thinking about it, I bet that if it's compatible with the Gypsy (which controls the machine through the USB port), it probably WILL still work with the old version of MTC that I still have; unless of course they require a Gypsy firmware upgrade to change the crypto keys...

Rumor has it the original keys were revealed by simply decompiling the Cricut Design Studio software; but, I refuse to have anything to do with hacking the crypto due to DMCA restrictions and PC's proven willingness to sue.

OTOH, my personal feeling on the CPU architecture change is that it's likely they are no longer using Atmel processors anymore, and thus probably not too inclined to go after firmware hacks for the old machines, especially if I'm not using their precious private keys. It would be neat to try reflashing one of the PIC models, but I don't have any experience or bandwidth or even much interest to pursue that.

The supply of broken ones on eBay has also shifted dramatically to Imagines (which combine printer & cutter functions into one unit) which I also am not too interested in messing with.

My latest progress on the older ones is that I've written "pins_arduino.h" files for both the ATmega1281 and ATmega16 (used in the cartridges), for the purpose of being able to leverage Arduino libraries and perhaps to port a Reprap firmware like Teacup. The ports seem to work fairly well, but I haven't done much yet with them so far other than to flash an LED.

-David

[Steve Baker]

I looked into it too - the inability to drive them from computer with your
own designs makes them useless.

The company seems to be taking the line of printer manufacturers (cheap
printer crazy expensive ink cartridges) and game consoles (cheap console,
expensive games) and phones/tablets (cheap phone, locked-in service
contract, "app-store" software) - meaning that they'll lose money on
machines that they sell if they can't sell design cartridges along with
them.

That business model is just *evil* - but it's everywhere.

IMHO, the best way forward is to figure out how to replace the Cricut's
onboard computer with an Arduino - then there is a very good set of
OpenSource tools to get designs into an Arduino using G-code - and from
there it's easy.

Not getting sued is tougher.

-- Steve

-- Steve

[Paul Bonser]

Yeah, I think replacing the firmware is a better option, really, or even replacing the control hardware completely, and just using the mechanical bits and motors from the original board.

Is there a USB-to-serial chip in there, or is the chip itself doing the USB?

[Marshall Vaughan]

It would be nice to collaborate on our use of stepper-motor control board so that we could be consistent about this.

We could, say, standardize on RepRap electronics for now. Maybe develop our own control boards later?

Oh look, this thing is black-boxed and broken by design, let's rip out the box and coopt the parts we can use.

Do you feel that's a worthwhile project David?

[Marshall Vaughan]

Right, citation:

http://reprap.org/wiki/%22Official%22_Electronics

[David Mitchell]

Didn't really mean to get this whole discussion going again, we debated all this a year or so ago last time I was messing with it.

The old hardware has a FT232 on board for the USB/serial, using its built-in XON/XOFF flow control (i.e., the firmware sends Xon/Xoff to the FT232, which then stops & starts the dataflow over USB link. RTS/CTS lines on the chip are simply connected together.

My own opinion is there's no reason to replace the hardware, everything you need is already there unless you feel like you just HAVE to have microstepping.

The Reprap code expects step/direction drivers for the motors, but I don't see why you couldn't provide a simple function to change those calls into the actual stepper phases required by the hardware. Last year I got as far as getting the "high torque half stepping" to work which I thought might run a bit smoother, but ran off the rails when it came to handling the acceleration. (reference: http://www.piclist.com/tecHREF/io/stepper/linistep/halfstep.htm)

-David

[Amishacker]

Didn't really mean to get this whole discussion going again, we debated all this a year or so ago last time I was messing with it.

Yeah, I don't want to debate it, I think it's pretty useless to replace electronics for a cricut - except in that it teaches crude hardware interfacing.

That's reason enough for me to just try it.