What do you think about that...

What do you think about that for controlling the stepper with a computer and that Control Multiple Stepper Motors Through A PC's USB Port ?

I got already a spare computer, my idea is to have a computer that will be use only for printing and a low cost driver for stepper, instead of a 200$ RAMPS.

USB has latency issues. You will have all kinds of problems trying to control stepper motors directly from a USB port. If you really want to directly control it from your computer, look at Mach3 or EMC2. Both require a parallel port though.

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That circuit is using a USB to FIFO, so it's probably possible as long as the FIFO isn't too small.
Having said that you should price everything out, you'd still need 4 stepper drivers, at least 2 mosfets for the heate bed and Hotend, 2 analog inputs to measure temperature, and 3 digital inputs for end stops.
I'll bet something like a sanguino or printer board will be cheaper than you can make a board for.
The only thing you're really saving is the micro controller and that might end up being the cheapest way to be the analog inputs, and PWM outputs.

Speedy Wrote:
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> What do you think about that for controlling the
> stepper with a computer and that Control Multiple
> Stepper Motors Through A PC's USB Port ?

I don't think that design would work at all for a printer controller. You'd have to replace the 2803 drivers as they are low current. It be might usable if you just want to control positioning, i.e dont care about velocity. Getting a reliable step rate with that setup would be next to impossible.

> I got already a spare computer, my idea is to have
> a computer that will be use only for printing and
> a low cost driver for stepper, instead of a 200$
> RAMPS.

I think there is some scope for simplifying the printer controller, but even if you replace the Arduino functions with PC software, it doesn't save a great deal of cost. In practice you would still need some form of programmable logic, or small microcontroller, to handle irregular comms rate and translate it to a regular step pulses, and probably handle accel/decel profiles as well. In which case you are pretty close to what the Arduino does already.

Getting PC software whether on Windows or Linux to reliably operate at the level of real-time required is a nightmare, it's worth spending money on external hardware to avoid having to delve into writing device drivers or builidng custom kernels.

There is a board for CNC called Smoothstepper which is a USB based stepper control, it uses an FPGA. It costs $155 and does not have motor drivers and all the other functions required for a printer controller.

prntrboard costs about $140, that is actually a pretty good price for what you get.

... as the syncing with the USB-FIFO is made on the PC side, it's not suitable for applications, that needs RT or asyncronous beheaviour, like multi-axes NC-applications (e.g. a 3D-printer).

An arduino (or any µC) is better suitable for this, as they have absolute timing control over the application, what eliminates the need for RT-OS or precise bus-syncing on the PC-side.

Look for small-size AVR-boards - I've made some 'fast-develop'-applications with BoArduinos, buth there are some other comparable boards/kits that may be cheaper, faster or better fitting to special needs ...

The common 'problem' with µC's is the need of knowing their specific native language too, beside your high-level programming skills on the PC.
So Arduino with it's Java/Procesing brand of programming language (and other similar µC- and Micro-PC-boards too) lowered the entry barrier to embedded control and started a new development rush around advanced 'home-brew'-electronics ...

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Viktor
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