joecarb89
Posts: 7
Joined: Sat May 04, 2013 10:27 pm

Reading joysticks inputs

Mon May 13, 2013 12:31 am

Hello, I am working on a project where I read a USB joystick's inputs and convert it to a PPM stream. It technically isn't gaming but I figured this would be my best bet at getting an answer since it deals with reading the USB inputs from a gaming device.

My project is very similar to this arduino project:

http://forum.arduino.cc/index.php/topic,8755.0.html

Pretty much, I want to use a joystick to fly my planes AND learn about Raspberry Pi. With an arduino, I would just read the buttons and potentiometers and convert it to PPM but I want to interface with USB.

So, is there any add-ons to python that would let me read the inputs? I think that is my biggest hurdle right now. I was going to use the Rpi's audio jack to output the signal, but that is a battle for another day (and sub forum).

Thanks!

scotty101
Posts: 3800
Joined: Fri Jun 08, 2012 6:03 pm

Re: Reading joysticks inputs

Mon May 13, 2013 9:46 pm

Pygame should allow you to access the joystick.

http://www.pygame.org/docs/ref/joystick.html
Electronic and Computer Engineer
Pi Interests: Home Automation, IOT, Python and Tkinter

User avatar
paddyg
Posts: 2462
Joined: Sat Jan 28, 2012 11:57 am
Location: UK

Re: Reading joysticks inputs

Tue May 14, 2013 7:48 am

Or if you use pi3d you can plug pretty much anything into the USB and read it with the Events module http://pi3d.github.io/html/FAQ.html the Silo.py demo uses this
I'm sure there's python libraries to send your output to the GPIO pins
also https://groups.google.com/forum/?hl=en-GB&fromgroups=#!forum/pi3d

joecarb89
Posts: 7
Joined: Sat May 04, 2013 10:27 pm

Re: Reading joysticks inputs

Wed May 15, 2013 6:45 pm

I was able to get the RPI to run the example code off the pygame website and it works well. The only thing is, it makes the RPI run at 100% CPU and +5c degrees hotter. I tried to install PI3D but I am having troubles unzipping it.

Now I just gotta figure out how to use the audio port to put out a PPM signal.

Just a note on the pygame example code, for anyone who finds this thread later on. The script calls for a class called def print. It won't run- you have to capitalize the P in print for all related functions. So it becomes def Print and textPrint.Print. I reposted it just in case if anyone is interested.

Code: Select all

import pygame

# Define some colors
BLACK    = (   0,   0,   0)
WHITE    = ( 255, 255, 255)

# This is a simple class that will help us print to the screen
# It has nothing to do with the joysticks, just outputing the
# information.
class TextPrint:
    def __init__(self):
        self.reset()
        self.font = pygame.font.Font(None, 20)

    def Print(self, screen, textString):
        textBitmap = self.font.render(textString, True, BLACK)
        screen.blit(textBitmap, [self.x, self.y])
        self.y += self.line_height
        
    def reset(self):
        self.x = 10
        self.y = 10
        self.line_height = 15
        
    def indent(self):
        self.x += 10
        
    def unindent(self):
        self.x -= 10
    

pygame.init()
 
# Set the width and height of the screen [width,height]
size = [500, 700]
screen = pygame.display.set_mode(size)

pygame.display.set_caption("My Game")

#Loop until the user clicks the close button.
done = False

# Used to manage how fast the screen updates
clock = pygame.time.Clock()

# Initialize the joysticks
pygame.joystick.init()
    
# Get ready to print
textPrint = TextPrint()

# -------- Main Program Loop -----------
while done==False:
    # EVENT PROCESSING STEP
    for event in pygame.event.get(): # User did something
        if event.type == pygame.QUIT: # If user clicked close
            done=True # Flag that we are done so we exit this loop
        
        # Possible joystick actions: JOYAXISMOTION JOYBALLMOTION JOYBUTTONDOWN JOYBUTTONUP JOYHATMOTION
        if event.type == pygame.JOYBUTTONDOWN:
            print("Joystick button pressed.")
        if event.type == pygame.JOYBUTTONUP:
            print("Joystick button released.")
            
 
    # DRAWING STEP
    # First, clear the screen to white. Don't put other drawing commands
    # above this, or they will be erased with this command.
    screen.fill(WHITE)
    textPrint.reset()

    # Get count of joysticks
    joystick_count = pygame.joystick.get_count()

    textPrint.Print(screen, "Number of joysticks: {}".format(joystick_count) )
    textPrint.indent()
    
    # For each joystick:
    for i in range(joystick_count):
        joystick = pygame.joystick.Joystick(i)
        joystick.init()
    
        textPrint.Print(screen, "Joystick {}".format(i) )
        textPrint.indent()
    
        # Get the name from the OS for the controller/joystick
        name = joystick.get_name()
        textPrint.Print(screen, "Joystick name: {}".format(name) )
        
        # Usually axis run in pairs, up/down for one, and left/right for
        # the other.
        axes = joystick.get_numaxes()
        textPrint.Print(screen, "Number of axes: {}".format(axes) )
        textPrint.indent()
        
        for i in range( axes ):
            axis = joystick.get_axis( i )
            textPrint.Print(screen, "Axis {} value: {:>6.3f}".format(i, axis) )
        textPrint.unindent()
            
        buttons = joystick.get_numbuttons()
        textPrint.Print(screen, "Number of buttons: {}".format(buttons) )
        textPrint.indent()

        for i in range( buttons ):
            button = joystick.get_button( i )
            textPrint.Print(screen, "Button {:>2} value: {}".format(i,button) )
        textPrint.unindent()
            
        # Hat switch. All or nothing for direction, not like joysticks.
        # Value comes back in an array.
        hats = joystick.get_numhats()
        textPrint.Print(screen, "Number of hats: {}".format(hats) )
        textPrint.indent()

        for i in range( hats ):
            hat = joystick.get_hat( i )
            textPrint.Print(screen, "Hat {} value: {}".format(i, str(hat)) )
        textPrint.unindent()
        
        textPrint.unindent()

    
    # ALL CODE TO DRAW SHOULD GO ABOVE THIS COMMENT
    
    # Go ahead and update the screen with what we've drawn.
    pygame.display.flip()

    # Limit to 20 frames per second
    clock.tick(20)
    
# Close the window and quit.
# If you forget this line, the program will 'hang'
# on exit if running from IDLE.
pygame.quit ()

mpolaczykpl
Posts: 3
Joined: Tue May 21, 2013 9:53 pm
Location: Poland
Contact: Website

Re: Reading joysticks inputs

Tue May 21, 2013 10:05 pm

Hi, I have similiar project but for two wheel-er robot. If you are still interested, I've made some post about reverse engineering of usb joystick communication protocol. I'm going to write python code for this in next month... just for fun :) http://mpolaczyk.wordpress.com/2013/05/ ... -protocol/
http://mpolaczyk.pl
software, robotics, engineering & geeky stuff…

User avatar
paddyg
Posts: 2462
Joined: Sat Jan 28, 2012 11:57 am
Location: UK

Re: Reading joysticks inputs

Wed May 22, 2013 8:36 am

joecarb, as you're just putting a few bits of text on screen you might be able to reduce the graphics load by just changing the rectangles you need rather than re-painting the whole screen. Using the gpu (as in pi3d) this doesn't make much difference as it's so quick but for pygame it might help.

Also I would like to know what your unzipping troubles where and if you got pi3d running. It may be a bit over the top to have all the 3d graphics to hand but rurwin's events module (mouse, keyboard, joystick etc) is very capable.
also https://groups.google.com/forum/?hl=en-GB&fromgroups=#!forum/pi3d

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