hello...
I need some help with my proj...
i wont to connect the ARDUINO MEGA to the USB HOST SHIELD
and connect it to the LOGITECH 3D PRO JOYSTICK
when the joystich will move forward , the THROTTLE will strat , and the MOTOR will start rotate
when the joystick will move right or left the weels will go right or left ....
im using a CURTIS CONTROLLER for the motor ....
can someone help ??? its really important to me...
really dont enen know how to start this 
let's get your mind right about where you are: this is not the place where cute cartoon animals sing happy songs while they do your homework for you.
this is Star Fleet Academy, and you are expected to be Wesley Freaking Crusher. you are expected to be a self starter who figures things out for yourself. you ask beginner questions, but you don't seem to have begun by yourself.
look through the Project Hub for projects involving joysticks and motors. find code that does what you want done, cut and paste and weave and splice until the code you mined and fused together compiles. come back when it doesn't work the way you expected it to.
look for libraries for joysticks and servos and motors, look in the examples files, see how things are done, then do them.
I find that the majority of useful advice I get here is one line:
study sprintf
use arrays
{ curly brackets have a purpose }
and you research on your own.
don't expect other people to build your log cabin, don't expect other people to break your logjam. be content with someone pointing to the log you have to move to free up the logjam.
notice the number of people with "we will not write code for you" and "we can spot laziness" in their signature lines.
help is provided to those who have earned it. help is provided to people who want to know why the code they wrote does not do what they expect. help is not provided if you show no code, no schematic, no progress to this point.
see this thread for an example of my point: Display text by line from SDCARD - Project Guidance - Arduino Forum
And as almost always we need more detail. What is a CURTIS CONTROLLER? What motor are you talking about? Links to datasheets please.
Oh and exactly what vehicle is it? How is it going to be powered? How many wheels and how will the wheels go left or right?
Steve
slipstick:
What is a CURTIS CONTROLLER?
I know it as something you might find controlling motor speed in an electric golf cart. But without elaboration by OP, who can say?
the conntroller is 1234 of curtis ; the proj is a 1/4 scale tractor (mini tractor)
there are two curtis controllers connected by CAN and they have a throttle (Potentiometer) ,
and another Potentiometer to select the ANGELE of the wheels.....
I want that the JOYSTICK by moving it forward or backword, the throttle will go ;
and by moving the JOYSTICK left or right will wove the wheels ....
slipstick:
And as almost always we need more detail. What is a CURTIS CONTROLLER? What motor are you talking about? Links to datasheets please.Oh and exactly what vehicle is it? How is it going to be powered? How many wheels and how will the wheels go left or right?
Steve
curtis conteroller - two conterollers 1234 connected by CAN ;
the motor is powred by the conteroller , and the controller by 24 volt +- ;
the motor is AC 10kW ashwood
A good start would be to draw a block diagram (use Visio, Diagramly or draw.io etc).
You have two Curtis controllers, I'm guessing one each driving the left and right traction motors? The tractor will steer by differential drive?
The two axes of the joystick will be used to produce throttle inputs to the two controllers; Type 4 throttle inputs (2.5V = off, 0V = full reverse, 5V = full forward.) Without thinking too much maybe you need a couple of DACs; the Mega reads the USB joystick and drives the two DACs to produce the needed voltages for each motor?
re the CAN bus: Is that connected only between the two controllers or is there an external connection? Do you intend to communicate with the controllers over CAN from the Mega?