After a few hours of research here and elsewhere I'm asking for help.
We've designed an instrument for our educational models (www.emriver.com) that uses a simple cone valve moving up and down just a few mm, driven by a stepper motor.
The prototype works wonderfully with the Adafruit motor shield and just a few lines of code. But we need to go to higher power now; probably a Gecko unit. This means a switch from the beautifully simple AFMotor.h library to something else that sends step and direction to a driver.
I've found tons of information, but seems there a many ways to do this (and none with a library). And I'm getting buried in details -- we just need double coil step and direction; the valve moves up and down. That's about it! I can't tell if the Arduino Stepper library can do this with external hardware; nobody mentions it.
There are references to Tom Igoe's nice site (http://www.tigoe.net) but pages are down and his tutorials refer to out of date libraries.
Sparkfun's Easydriver page http://www.sparkfun.com/products/10267 has a bunch of links, and so does the Easydriver site, but many are outdated and overly complex. Good links in the comments, but what a mess (fix that Sparkfun, geez).
We can simply "bit bang" the driver with for loops (e.g. here: Dan Thompson: EasyDriver v3.1 Tutorial) but would be nice to use a library and a few lines of code.
My question: Can the Stepper library be made work with a step/direction driver?
If not, what's the simplest way to do this?