Stepper motor and encoder perfect 1:1

Need help with coding a stepper motor and encoder with perfect one to one movement at any (High)speed and direction

i would probably use two ardunios to do this over i2c or serial. let the master drive the stepper, prior to stepper start notify the i2c (or serial) slave to start looking for counts. once the master thinks he is nearly done he can ask for a count. and you could always add a hardwired stop from the slave to that for good measure to let the slave tell the master not ready or STOP! That same hardwire could be used as a soft stop manual pushbutton. Also depending on what you are moving, an Estop on the Power to the DRIVER is a good idea.

nah just one of these per axis...self correcting closed loop....

they (other vendors) have them at a higher price with stall detection PRIOR to a missed step.

http://www.abiry.com/media/1390984014.pdf

If you connect two steppers together and move the shaft of one, the other will move in sync. Just sayin... you may not need that encoder after all.

Depends on what "high speed" means. I bought a stepper motor a while back to fool with. I found that if I drove it any faster than 4ms per step - which the arduino can easily do - it would start to skip.

What sort of encoder are we talking about? A quadrature encoder? If you just need 1:1, you could wire up the encoder to the stepper electronically, no arduino required. One track of the encoder drives coils A/~A, and the other track drives coils B/~B. The layout of a quadrature encoder means that it will send the signal in the correct sequence to keep the steeper in sync.