When I was young, I had two unipolar (don’t know that detail since this week) stepper motors. My pleasure was to connect them together and when I spinned one, the other performed nearly the same rotation. It was a great pleasure to play with. But I finally make one (bipolar) really work today. Yeah! I work hard to understand the motor I got, the MITSUMI M42SP-4. When I look over the Net to find some specs, it’s never what my motor look like. So I guest a four wires bipolar, and I tried it on 5v, safely. Something append, but not correctly. Any bad connections with the L293D? I think not. I found, after a while, that my problem was the Arduino stepper library. I don’t know if I was doing something wrong but it’s look like the stepper function always stimulate both coils at the same time. So I coded an ugly function to recreate the four steps needed, and Bingo! This will make my projet go further.
Give a look at the alpha release of DuinOS: a free full open source RTOS with preemptive multitasking for Arduino. It’s based on the FreeRTOS kernel. I had no time to try this now, but I’ll check it later. Thanks Juilán.