Controlling 2 stepper motors with joystick

I have an Arduino Uno, CNC shield v3 ,Driver a4988, a dual-axis xy joystick module, that I want to use to control two stepper motors (Type: 17HS4401S). The idea is that Y axis on joystick controls stepper motor and X axis 2.nd stepper motor, is that possible over CNC shield?

Whilst certainly do-able you chose a longer method to do it.
I would have just gotten two suitable drivers and gone from there.

Now you have to work out what pins are spare on the shield to add your joystick.

And of course what type of joystick ?
Are you going to use the microstepping ability ?
What are you using for a power supply ?
How much load / torque will you be putting on the steppers ?

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It will help you get the best out of the forum in the future.

These links may help

Stepper Motor Basics
Simple Stepper Code

You will probably need access to two of the Arduino's analog pins to read the joystick potentiometers.

You will probably also need two limit switches (one for each motor) that can be triggered by the motor to establish the HOME or ZERO position at startup.

What do you want to use the stepper motors for? It is much easier to give useful advice when you tell us what you are creating.