Ok the first 555 pwm built and tested ok using a transistor to drive motor. I could not find any digi-pots thus far so I used a manual variable resistor and the motor responds well all the way from +-3 to 12 volts. I settled on the circuit here http://www.cpemma.co.uk/555pwm.html
Does anyone perhaps have experience with emulation of the spi protocol, I am just concerned with the clock speeds or is it synchronous like a shift register?