For example, if I wanted to implement a hardware stepper motor controller using an Arduino, and I wanted to drive that controller with another Arduino, could I just run the digital pins from the master Arduino to the digital pins of the slave Arduino and read the output with the slave Arduino?
A motor controller typically uses two pins per motor - one for direction control and one for stepping. If the Arduino sending the signals has two pins to spare to send data to the other Arduino with the motor shield, what's the benefit of a second Arduino. Just drive the motor controller directly.
When downloading new programs I had to remove the serial wire, else the slave display went crazy trying to display all the code
You either wait a short time before sending another command (which would be the normal case anyway) or have a third handshaking line.
is that what you meant by 'wait a short while before sending another command'?
50,000 steps per revolution,
if (direction == CCR) // set direction pin high or low asm ("cbi PORTx,PIN_DATA");else asm ("sbi PORTx,PIN_DATA");asm ("sbi PORTx,PIN_CLOCK"); // pulse interrupt pinasm ("cbi PORTx,PIN_CLOCK");
That's a lot, what's the RPM? A lot depends on that.