Is it possible to control NEMA17 stepper motors with a keyboard so that when a key is pressed, the motor will rotate until the key is released?
What sort of keyboard?
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Is the keyboard attached to the Arduino or a PC ?
Its a Dell keyboard with a USB
I have been trying to connect the keyboard directly to the Arduino.
Yes, most likely.
Is the keyboard on the PC or a keypad (3x4 or 4x4)?
What Arduino? What stepper driver?
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Do you have to use a keyboard ?
Would a simple pushbutton be acceptable ?
Which Arduino. Does it have native USB like a Leonardo?
Which Arduino?
It is a full PC keyboard, I am using an Arduino Mega 2560, and I am using tb6600 stepper motor drivers to control the stepper motors.
Can you use a Leo to read a USB device ?
I need to use many buttons and I was hoping I could use a keyboard that I already had instead of making a circuit with multiple pushbuttons.
My mistake. Leonardo can act as a USB keyboard (send keystrokes to PC), but, apparently, cannot read a USB keyboard.
How many ?
How many buttons? A 4X4 keypad has 16 buttons and is pretty easy to interface, though it takes 8 pins.
You can bring the pin usage down to 2 pins using an I2C expander with the 4x4 keypad.
https://www.hackster.io/mitov/i2c-matrix-keypad-with-pcf8574-pcf8574a-gpio-and-visuino-dbf72c
I'm not sure exactly how many but I need to control about 25 motors with a button for both directions of rotation.
What sort of application is this for ?
How about a method of selecting which motor is to be controlled then, with the motor selected, a button for each direction ?
I was going to control a robot by controlling many stepper motors simultaneously.
A maximum of 10 at the same time at most, presumably 
I might be able to work with only 10 at the same time. How exactly would I connect the keyboard to the Arduino?