Homebrew PCBs

It should work fine if you set the serial port driver in your computer to
use software flow control (XON/XOFF) and in Cricut program the
receiving function should send XOFF when ring buffer is full, then
it will keep reading/processing input and when you reach the low
watermark (half buffer?) send XON to start data flow again.

raymundo





>________________________________
> From: David Mitchell <gossiphog@...>
>To: Homebrew_PCBs@yahoogroups.com 
>Sent: Friday, June 22, 2012 7:27 AM
>Subject: Re: [Homebrew_PCBs] Re: Produce Quick & Cheap PCBs with a CNC paper cutter
> 
>
>  
>Getting the Cricut machine to talk HPGL is a project I was working on
>for several months last year. I based my work on an extension of the
>"Freecut" firmware written for the Cricut Personal.
>
>(see https://github.com/Arlet/Freecut)
>
>I've ported it to the Cricut Create, and it does indeed speak a few
>HPGL-like commands, but the place where I've gotten stuck is with
>flow-control. My plan was to support the commands that other vinyl
>cutters support (like the Black Cat, Roland, or US Cutter). This
>firmware does require re-flashing the unit via ICSP programmer
>connected through the cartridge port, which also irretrievably
>overwrites the original firmware.
>
>The Cricut has a FTDI chip on it providing the USB interface to the PC
>which (from my understand) transparently converts XON/XOFF signals
>from the onboard processor into USB flow control signals that the PC
>obeys.
>
>Unfortunately, the serial library I used (Fleury) does not support
>software flow control, so unless you type your commands very slowly
>into a terminal window, the machine skips most of them. The hardware
>flow control lines on the FTDI are not connected to the Cricut's
>processor, so this is not an option.
>
>I started a private google group a while back with the purpose of
>collaborating on it, but unfortunately noone else has taken up the
>project since I got bored of it and moved on. I would love to find
>someone with more motivation and a little better C skill than I to
>finally solve the flow control problem. (see
>https://groups.google.com/d/forum/ccfwhack).
>
>Another idea I had that might be simpler to implement is a PC
>parallel-port adapter to Cricut cartridge adapter cable, sending
>encoded stepper control signals directly from PC to cricut via 1 mbps
>SPI, and a thin firmware on the cricut that would obey those signals.
>The PC would run something like LinuxCNC, using a custom configuration
>for the parallel port driver.
>
>I don't believe the USB interface is capable of fast enough throughput
>to handle direct stepper phase control, but step-direction commands
>might work. (flow control would still be an issue).
>
>Here's a page linking to photos of the Cricut Personal, Expression,
>and cartridge hardware. They control the stepper windings directly
>rather than with dedicated stepper driver hardware. Cutting pressure
>is via PWM to a voice coil in the cutter solenoid.
>
>http://www.built-to-spec.com/cricutwiki/index.php?title=Main_Page
>
>I have several Expressions as well, which have the same processor as
>the Create, but will need some additional code changes to support the
>larger screen, additional keyboard buttons, and larger cutting area.
>
>Anyhow, if you're seriously interested, join the list above. I can
>potentially provide some dev hardware as well.
>
>-David
>
>On Fri, Jun 22, 2012 at 7:43 AM, jeremy youngs <jcyoungs76@...> wrote:
>> linuxcnc outputs step/dir directly and is configurable and needs no signal
>> conditioning before a l293/97 etc. conditioning or coding is only necessary
>> for microprocessors. i have three sla7086 printer stepper setting on my
>> bench now that run just fine
>>
>> On Fri, Jun 22, 2012 at 7:36 AM, Tony Smith <ajsmith1968@gmail.com> wrote:
>>
>>> **
>>>
>>>
>>> > LinuxCNC (or anything else for that matter) won't talk to the CriCut,
>>> you'd have
>>> > to add your drivers and bypass all the electronics. Most of these things
>>> use some
>>> > form of HPGL, or mangled a bit to provide security (presumably that's how
>>> it
>>> > was reverse engineered).
>>> >
>>> > not necessarily true some printers run a simpl l293, 278 or 298 that will
>>> directly
>>> > communicate with lcnc, i know ive built them, however if your machine is
>>> > operated via microprocessor without the source code it will not work as
>>> you
>>> > say. This is why i said the pinout was necessary as if it has enable
>>> input
>>> , or bus
>>> > line it probably will not work, if it has simple step and direction
>>> inputs
>>> as per the
>>> > ic mebtioned above I could make it work. I say try it the only thing he
>>> has to lose
>>> > is some time.
>>>
>>> Well, what I meant was there will be some electronics before the stepper
>>> drivers (293 etc), that converts the HPGL (or whatever) to Step &
>>> Direction.
>>> Some use weird driver chips simply replacing the lot is easier than
>>> figuring
>>> it out.
>>>
>>> You can't just plug it in as it and expect it to work.
>>>
>>> Tony
>>>
>>>
>>>
>>
>>
>>
>> --
>> jeremy youngs
>>
>>
>> [Non-text portions of this message have been removed]
>>
>>
>>
>> ------------------------------------
>>
>> Be sure to visit the group home and check for new Links, Files, and Photos:
>> http://groups.yahoo.com/group/Homebrew_PCBsYahoo! Groups Links
>>
>>
>>
>
> 
>
>

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