Joystick and Gamepad Input

=Joystick and Gamepad Input= 
//Rod//
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=Reading the gameport=port= 
Your PC supports quite a variety of input devices. In modern parlance they are called HIDs (Human Input Devices), keyboards, mice, graphic pads, touchscreens and an old stalwart, the joystick or game pad. Now there use to be a dedicated joystick port , laterally called a game port, on every PC.

That has fallen away and since Vista the game port is no longer supported. It matters not a whit to Liberty BASIC as it is perfectly capable of reading and dealing with HID devices which are most often connected via USB, (Universal Serial Bus).

In most cases the native command set is all that you will need. READJOYSTICK (n) will read the current status of joystick (n). (n) can be 1 or 2. So you can plug in two, USB based, standard two or three axis joysticks and use their input very easily in your Liberty BASIC programs.

But it does not end there. With API calls you can read in up to six axis of movement from up to sixteen devices and on top of that read in the status of up to sixteen buttons from each device!

But lets start simply.

A simple joystick will usually support two axis of movement, X and Y and two buttons. The axis of movement are returned as numbers between 0 and 65535 (256*256). 0 means fully down, 32767 or thereabouts means centred and 65535 means fully up. I say thereabout because the game pad input is a little erratic.

It is erratic because it is cheap and cheerful but nevertheless extremely efficient and useful. Whatever hardware supplies the readings, be it on your PC, on a PCI card or on a USB based dongle, it operates essentially the same way. The stick moves a potentiometer, a pot, a variable resistor. This resistor controls how fast a capacitor discharges, the reading is taken by timing when the voltage across it falls from +5v to +0v, 1 or 0 in computer speak. The time interval will be short if the resistance is low and high if the resistance is high. This is what supplies the "analog" nature of the input.

It is a fast, repetitive process. The timing of the pulse to charge the capacitor, the temperature, mechanical variance and the graininess of the graphite on the pot all contribute to the erratic nature of the raw data. You can calm it down with algorithms.

The wiring of these devices is pretty simple no matter how complex the physical device actually looks. If you want some fun you can hack any old cheap device and get a myriad of robotic or measurement devices connected to Liberty BASIC provided you measure resistance (100k) or button closure.

[[image:joy.png]]




[[code format="lb"]]
'define a struct for joyinf read, standard two axis joystick 'for
'for more info [[http://msdn.microsoft.com/en-us/library/windows/desktop/dd757110(v=vs.85).aspx]] struct joy0,_ x as long ,_ 'x axis 0 - 65535 with 32767 as centre y as long ,_ 'y axis z as long ,_ 'z axis if it exists buttons as long 'bits set by button press

'definestruct joy0,_ 
x as long ,_ 'x axis 0 - 65535 with 32767 as centre 
y as long ,_ 'y axis 
z as long ,_ 'z axis if it exists buttons as long 'bits set by button press

'define a struct for joyinfoex read, gampads, car simulators and flight sim yokes 'for
'for more info [[http://msdn.microsoft.com/en-us/library/windows/desktop/dd757112(v=vs.85).aspx]] struct

struct joyex0,_ size as long,_ 'size of struct flags
flags as long,_ 'what to check x
x as long,_ 'x axis y
y as long,_ 'y axis z
z as long,_ 'z axis r
r as long,_ 'r axis u
u as long,_ 'u axis if it exists v
v as long,_ 'v axis if it exists buttons
buttons as long,_ 'bits set by button press buttonNumber
buttonNumber as long,_ ' number of buttons pressed pov
pov as long,_ 'point of view value reserved1
reserved1 as long,_ reserved2
reserved2 as long
'store

'store the size of the struct and set the flag value for the info we want sizeStruct
sizeStruct = len(joyex0.struct) joyex0.size.struct=sizeStruct joyex0.flags.struct=1
joyex0.size.struct=sizeStruct 
joyex0.flags.struct=1 or 2 or 4 or 8 or 128 'ie xyzr axis and buttons info returned

joy=0 'joysticks can be numbered 0-15 replicate the calls and structs for additional joysticks
timer 250,[readit] wait
[readit] cls
'native read 'restricted to three axis and buttons 1 and 2 readjoystick 1 'actually joy 0 print "joy0 X ";Joy1x,"Y ";Joy1y,"Z ";Joy1z,, Joy1button1+Joy1button2
'standard api read 'restricted to three axis but can read all buttons calldll #winmm, "joyGetPos", joy as long, joy0 as struct , result as long print "joy0 X ";joy0.x.struct,"Y ";joy0.y.struct,"Z ";joy0.z.struct,,joy0.buttons.struct
'extended info api read 'up to six axis if they exist and all buttons calldll #winmm, "joyGetPosEx", joy as long, joyex0 as struct , result as long print "joy0 X ";joyex0.x.struct,"Y ";joyex0.y.struct,"Z ";joyex0.z.struct," R ";joyex0.r.struct,joyex0.buttons.struct
wait

[readit]
cls

'native read 'restricted to three axis and buttons 1 and 2 
readjoystick 1 'actually joy 0 
print "joy0 X ";Joy1x,"Y ";Joy1y,"Z ";Joy1z,, Joy1button1+Joy1button2

'standard api read 'restricted to three axis but can read all buttons 
calldll #winmm, "joyGetPos", joy as long, joy0 as struct , result as long 
print "joy0 X ";joy0.x.struct,"Y ";joy0.y.struct,"Z ";joy0.z.struct,,joy0.buttons.struct

'extended info api read 'up to six axis if they exist and all buttons 
calldll #winmm, "joyGetPosEx", joy as long, joyex0 as struct , result as long 
print "joy0 X ";joyex0.x.struct,"Y ";joyex0.y.struct,"Z ";joyex0.z.struct,"R ";joyex0.r.struct,joyex0.buttons.struct

wait

'determine if a button is pressed by anding its value against the button value. 'button 1=1 button 2=2 button 3=4 button 4=8 button 5=16 etc etc 'say button 2 and 5 are pressed thats 2+16=18 print 18 and 2 print 18 and 16
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=Second Part Title= 
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=Third Part Title= 
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