Vdd: 5V +/- 10%
Vss: 0V (ground reference)
A Step: Step input, step will be made on negative-going edge
A Dir: Direction input, is read when step line goes low
A1-4: Output for a unipolar motor in half-step sequence
B Step: Step input, step will be made on negative-going edge
B Dir: Direction input, is read when step line goes low
B1-4: Output for a unipolar motor in half-step sequence
MCLR: Master clear and Reset. This line must be held high for normal operation. Pull low to reset the chip.
OSC1/OCS2: Clock inputs - see diagram below for RC oscillator hookup.
Unused: Just like it says, leave this pin floating if you like. In Hakan Ertan's version, this selects full/half stepping.
Source code for the U-2 (a PIC 16F84 running a dedicated program) can be downloaded here and you can program the IC's yourself. If you don't have a PIC programmer or are feeling lazy, you can buy pre-programmed and tested chips from me for $10 apiece. See the ordering page for details.
Hakan Ertan has uploaded code that adds full/half-step selection on pin 3. Download his code here. He has also submitted code for a version that runs on the PIC12C508A microcontroller.
Here is a sample circuit schematic using the U-2 as a stepper driver for two unipolar motors (click view full-size)http://www.dakeng.com/u2source.zipPosted on: February 12, 2008, 09:01:16 21:01 - Automerged