clock driver for sparkfun easydriver breakout

This is a project I`ve done on behalf of a person on an internet forum. The requested operation is simple: Use an EasyDriver stepper motor driver and a 1. 8 deg/rotation stepper motor and make the motor turn one revolution per minute. This frees me up a bit not having to select and source products myself, nor having to implement the actual stepper
clock driver for sparkfun easydriver breakout - schematic

driver myself. The EasyDriver is REALLY simple in operation. Connect 7-30v DC to M+ (and ground to GND), connect a stepper motor to A and B and the motor automatically steps once for each LOW->HIGH transition on STEP. The direction is dependent on the state of DIR (+5v or ground). MS1 and MS2 together defines the step resolution. The driver chip is a Allegro A3967SLB, so the truth table for MS pins can be found in it`s datasheet, page 2. The breakout board has pull-up resistors on both MS1 and MS2, which puts it in eight-step resolution as standard. To alter MS1 and MS2 you simply pull them to ground individually based on your desired resolution. I decided to make a few improvements to the requested operation. Via a DIP-switch the user can select the resolution for the EasyDriver while simultaneously altering the steps/minute so it will always make one turn per minute even though the step resolution is changed. There is also an LED to indicate each step. I used a four-way DIP switch, the two remaining switches I used for step direction and to simply turn the steps on or off. The DIR signal is pulled up to +5v by a 10k resistor My circuit is built on a strip board and is based on an AtTiny25. It`s system clock is driven by a low frequency 32. 768kHz watch crystal. It`s important to program the correct fuse bits for low frequency crystal oscillators! On to the code. I`m using Timer 0 with system clock as clock source in...

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