Weaponizing our Robot - Robotics with Python Raspberry Pi and GoPiGo p.5

In Part 5 of the Robotics with Python, we'll be covering how to control the USB missile launcher:

USB Missile Launcher

If you're really looking to keep the peace, then we know how powerful mutually assured destruction can be. This USB missile launcher is essential for establishing the status quo in your domicile.

---

The software that comes with the GoPiGo has some example code for handling the USB cannon, only they have it built to work with a mouse. That's cool, but what if we wanted to have it keyboard controlled? It's also a good idea to tinker here, so you can get familiar with what is required to create code that will manipulate the launcher.

The first step here is to take a peak into how Dexter Industries controlled the cannon with the mouse:

#!/usr/bin/env python
########################################################################                                                                  
# This example controls the GoPiGo and Rocket Launcher with a wireless mouse on the USB port.
# The GoPiGo motion is controlled by the buttons of the.
# The Rocket Launcher is controlled by the motion of the mouse.
# The Rocket Launcher is fired by pressing the middle button.  
#                                
# http://www.dexterindustries.com/GoPiGo/                                                                
# History
# ------------------------------------------------
# Author     	Date      		Comments
# John Cole  	April 14  		Initial Authoring    
# Karan			27 June 14		Code cleanup and made more responsive   
# 				25 Aug  14		USB high current mode for Raspberry Pi Model B+ added        
#                                       
'''
## License
 GoPiGo for the Raspberry Pi: an open source robotics platform for the Raspberry Pi.
 Copyright (C) 2015  Dexter Industries

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see .
'''
#
########################################################################
from gopigo import *
import struct
import os

import sys
import platform
import time
import socket
import re
import json
import urllib2
import base64

import usb.core
import usb.util

#Enable for Model B+ and disable for Model B
model_b_plus=True	# For the model B+ we need to turn this variable on to run the Office Cannon.
					# This can be left on for the Model B and not cause problems.
					# This pulls GPIO 38 to high, which overrides USB overcurrent setting.
					# With this set, the USB can deliver up to 1.2 Amps.

# Protocol command bytes
DOWN    = 0x01
UP      = 0x02
LEFT    = 0x04
RIGHT   = 0x08
FIRE    = 0x10
STOP    = 0x20

DEVICE = None
DEVICE_TYPE = None

file = open( "/dev/input/mice", "rb" );
debug = 0

# Setup the Office Cannon
def setup_usb():
    global DEVICE 
    global DEVICE_TYPE

    DEVICE = usb.core.find(idVendor=0x2123, idProduct=0x1010)

    if DEVICE is None:
        DEVICE = usb.core.find(idVendor=0x0a81, idProduct=0x0701)
        if DEVICE is None:
            raise ValueError('Missile device not found')
        else:
            DEVICE_TYPE = "Original"
    else:
        DEVICE_TYPE = "Thunder"

    # On Linux we need to detach usb HID first
    if "Linux" == platform.system():
        try:
            DEVICE.detach_kernel_driver(0)
        except Exception, e:
            pass # already unregistered    
    DEVICE.set_configuration()

#Send command to the office cannon
def send_cmd(cmd):
    if "Thunder" == DEVICE_TYPE:
        DEVICE.ctrl_transfer(0x21, 0x09, 0, 0, [0x02, cmd, 0x00,0x00,0x00,0x00,0x00,0x00])
    elif "Original" == DEVICE_TYPE:
        DEVICE.ctrl_transfer(0x21, 0x09, 0x0200, 0, [cmd])

#Send command to control the LED on the office cannon
def led(cmd):
    if "Thunder" == DEVICE_TYPE:
        DEVICE.ctrl_transfer(0x21, 0x09, 0, 0, [0x03, cmd, 0x00,0x00,0x00,0x00,0x00,0x00])
    elif "Original" == DEVICE_TYPE:
        print("There is no LED on this device")

#Send command to move the office cannon
def send_move(cmd, duration_ms):
    send_cmd(cmd)
    time.sleep(duration_ms / 1000.0)
    send_cmd(STOP)

def run_command(command, value):
    command = command.lower()
    if command == "right":
        send_move(RIGHT, value)
    elif command == "left":
        send_move(LEFT, value)
    elif command == "up":
        send_move(UP, value)
    elif command == "down":
        send_move(DOWN, value)
    elif command == "zero" or command == "park" or command == "reset":
        # Move to bottom-left
        send_move(DOWN, 2000)
        send_move(LEFT, 8000)
    elif command == "pause" or command == "sleep":
        time.sleep(value / 1000.0)
    elif command == "led":
        if value == 0:
            led(0x00)
        else:
            led(0x01)
    elif command == "fire" or command == "shoot":
        if value < 1 or value > 4:
            value = 1
        # Stabilize prior to the shot, then allow for reload time after.
        time.sleep(0.5)
        for i in range(value):
            send_cmd(FIRE)
            time.sleep(4.5)
    else:
        print "Error: Unknown command: '%s'" % command

def run_command_set(commands):
    for cmd, value in commands:
        run_command(cmd, value)

#Read the values from the mouse
def getMouseEvent():
	buf = file.read(3)
	button = ord( buf[0] )
	bLeft = button & 0x1
	bMiddle = ( button & 0x4 ) > 0
	bRight = ( button & 0x2 ) > 0
	x,y = struct.unpack( "bb", buf[1:] )
	if debug:
		print ("L:%d, M: %d, R: %d, x: %d, y: %d\n" % (bLeft,bMiddle,bRight, x, y) )
	return [bLeft,bMiddle,bRight,x,y]
  
  
flag=0
#Control the office cannon
def control():
	global flag
	[bLeft,bMiddle,bRight,x,y]=getMouseEvent()  #Get the inputs from the mouse

	#GoPiGo control
	if flag==1: 			#If left or right mouse not pressed, move forward
		fwd()
		flag=0
	if bLeft:    			#If left mouse buton pressed, turn left
		left()
		flag=1
  
	if bRight:    			#If right mouse button presses, turn right
		right()
		flag=1
	if bLeft and bRight:  	#If both the left and right mouse buttons pressed, go back
		stop()
		flag=0
 
	#Office cannon control
	tdelay=80
	if bMiddle > 0:
		print "fire rockets"
		run_command("fire", tdelay)

	#Move the mouse left to move the cannon left
	#Move the mouse right to move the cannon right
	#Press middle button to fire
	
	if x == 0:
		print "Stop rockets"
	elif x > 10:
		print "Left rockets"
		run_command("left", tdelay)
	elif x < -10:
		print "Right rockets"
		run_command("right", tdelay)
	if y == 0:
		print "Stop Rockets Y"
	elif y > 10:
		print "Up Rockets"
		run_command("up", tdelay)
	elif y < -10:
		print "Down rockets"
		run_command("down", tdelay)

	time.sleep(.1)
	return
  
try:
	print "Setting up"
	print "Left Mouse button- Turn left\nRight mouse button- Turn right\nBoth left and right- Stop\nMiddle mouse button- Fire rocket\nMove mouse to control the launcher"
	setup_usb()
	
	#Enable USB to give supply upto 1.2A on model B+
	if model_b_plus:
		os.system("gpio -g write 38 0")
		os.system("gpio -g mode 38 out")
		os.system("gpio -g write 38 1")
	
	run_command("zero", 100)
	stop()
	print "Start\n............."
	while True:
	  control()
except KeyboardInterrupt:
	#Disable hight current mode on USB before exiting
	if model_b_plus:
		os.system("gpio -g write 38 0")

That's a lot of code, but we can begin to break it down. Looking into the run_command function, we can see what is done once the direction of the mouse is figured out. That's exactly what we want. We see that the syntax being used here is "send_move." We can then check that function out, but we're actually going to go ahead and mainly copy and paste significant portions of this script and paste them into our own.

With modifications:

##Much of this code comes from Dexter Industries' GoPiGo with office cannon script, with minor changes for user-input from a keyboard.
##
## http://www.dexterindustries.com/GoPiGo/                                                                
## History
## ------------------------------------------------
## Author     	Date      		Comments
## John Cole  	April 14  		Initial Authoring    
## Karan			27 June 14		Code cleanup and made more responsive   
## 				25 Aug  14		USB high current mode for Raspberry Pi Model B+ added        
##                                       
##
##
##License
##GoPiGo for the Raspberry Pi: an open source robotics platform for the Raspberry Pi.
## Copyright (C) 2015  Dexter Industries
##
##This program is free software: you can redistribute it and/or modify
##it under the terms of the GNU General Public License as published by
##the Free Software Foundation, either version 3 of the License, or
##(at your option) any later version.
##
##This program is distributed in the hope that it will be useful,
##but WITHOUT ANY WARRANTY; without even the implied warranty of
##MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
##GNU General Public License for more details.
##
##You should have received a copy of the GNU General Public License
##along with this program.  If not, see .

import Tkinter as tk
from gopigo import *

servo_range = [2,3,4,5,6,7,8]


import struct
import os

import sys
import platform
import time
import socket
import re
import json
import urllib2
import base64

import usb.core
import usb.util

#Enable for Model B+ and disable for Model B
model_b_plus=True	# For the model B+ we need to turn this variable on to run the Office Cannon.
					# This can be left on for the Model B and not cause problems.
					# This pulls GPIO 38 to high, which overrides USB overcurrent setting.
					# With this set, the USB can deliver up to 1.2 Amps.
tdelay=80
# Protocol command bytes
DOWN    = 0x01
UP      = 0x02
LEFT    = 0x04
RIGHT   = 0x08
FIRE    = 0x10
STOP    = 0x20

DEVICE = None
DEVICE_TYPE = None

file = open( "/dev/input/mice", "rb" );
debug = 0

# Setup the Office Cannon
def setup_usb():
    global DEVICE 
    global DEVICE_TYPE

    DEVICE = usb.core.find(idVendor=0x2123, idProduct=0x1010)

    if DEVICE is None:
        DEVICE = usb.core.find(idVendor=0x0a81, idProduct=0x0701)
        if DEVICE is None:
            raise ValueError('Missile device not found')
        else:
            DEVICE_TYPE = "Original"
    else:
        DEVICE_TYPE = "Thunder"

    # On Linux we need to detach usb HID first
    if "Linux" == platform.system():
        try:
            DEVICE.detach_kernel_driver(0)
        except Exception, e:
            pass # already unregistered    
    DEVICE.set_configuration()

#Send command to the office cannon
def send_cmd(cmd):
    if "Thunder" == DEVICE_TYPE:
        DEVICE.ctrl_transfer(0x21, 0x09, 0, 0, [0x02, cmd, 0x00,0x00,0x00,0x00,0x00,0x00])
    elif "Original" == DEVICE_TYPE:
        DEVICE.ctrl_transfer(0x21, 0x09, 0x0200, 0, [cmd])

#Send command to control the LED on the office cannon
def led(cmd):
    if "Thunder" == DEVICE_TYPE:
        DEVICE.ctrl_transfer(0x21, 0x09, 0, 0, [0x03, cmd, 0x00,0x00,0x00,0x00,0x00,0x00])
    elif "Original" == DEVICE_TYPE:
        print("There is no LED on this device")

#Send command to move the office cannon
def send_move(cmd, duration_ms):
    send_cmd(cmd)
    time.sleep(duration_ms / 1000.0)
    send_cmd(STOP)

def run_command(command, value):
    command = command.lower()
    if command == "right":
        send_move(RIGHT, value)
    elif command == "left":
        send_move(LEFT, value)
    elif command == "up":
        send_move(UP, value)
    elif command == "down":
        send_move(DOWN, value)
    elif command == "zero" or command == "park" or command == "reset":
        # Move to bottom-left
        send_move(DOWN, 2000)
        send_move(LEFT, 8000)
    elif command == "pause" or command == "sleep":
        time.sleep(value / 1000.0)
    elif command == "led":
        if value == 0:
            led(0x00)
        else:
            led(0x01)
    elif command == "fire" or command == "shoot":
        if value < 1 or value > 4:
            value = 1
        # Stabilize prior to the shot, then allow for reload time after.
        time.sleep(0.5)
        for i in range(value):
            send_cmd(FIRE)
            time.sleep(4.5)
    else:
        print "Error: Unknown command: '%s'" % command

def run_command_set(commands):
    for cmd, value in commands:
        run_command(cmd, value)

#Read the values from the mouse
def getMouseEvent():
	buf = file.read(3)
	button = ord( buf[0] )
	bLeft = button & 0x1
	bMiddle = ( button & 0x4 ) > 0
	bRight = ( button & 0x2 ) > 0
	x,y = struct.unpack( "bb", buf[1:] )
	if debug:
		print ("L:%d, M: %d, R: %d, x: %d, y: %d\n" % (bLeft,bMiddle,bRight, x, y) )
	return [bLeft,bMiddle,bRight,x,y]
  
  
flag=0
#Control the office cannon
def control():
	global flag
	[bLeft,bMiddle,bRight,x,y]=getMouseEvent()  #Get the inputs from the mouse

	#GoPiGo control
	if flag==1: 			#If left or right mouse not pressed, move forward
		fwd()
		flag=0
	if bLeft:    			#If left mouse buton pressed, turn left
		left()
		flag=1
  
	if bRight:    			#If right mouse button presses, turn right
		right()
		flag=1
	if bLeft and bRight:  	#If both the left and right mouse buttons pressed, go back
		stop()
		flag=0
 
	#Office cannon control
	
	if bMiddle > 0:
		print "fire rockets"
		run_command("fire", tdelay)

	#Move the mouse left to move the cannon left
	#Move the mouse right to move the cannon right
	#Press middle button to fire
	
	if x == 0:
		print "Stop rockets"
	elif x > 10:
		print "Left rockets"
		run_command("left", tdelay)
	elif x < -10:
		print "Right rockets"
		run_command("right", tdelay)
	if y == 0:
		print "Stop Rockets Y"
	elif y > 10:
		print "Up Rockets"
		run_command("up", tdelay)
	elif y < -10:
		print "Down rockets"
		run_command("down", tdelay)

	time.sleep(.1)
	return


def key_input(event):
    key_press = event.keysym.lower()
    print(key_press)

    if key_press == 'w':
        fwd()
    elif key_press == 's':
        bwd()
    elif key_press == 'a':
        left()
    elif key_press == 'd':
        right()
    elif key_press == 'q':
        left_rot()
    elif key_press == 'e':
        right_rot()
    elif key_press == 'space':
        stop()
    elif key_press == 'u':
        print(us_dist(15))

    elif key_press.isdigit():
        if int(key_press) in servo_range:
            enable_servo()
            servo(int(key_press)*14)
            time.sleep(1)
            disable_servo()

    elif key_press == 'control_r' or key_press == 'control_l':
        print('Fire rockets!')
        run_command("fire", tdelay)

    elif key_press == 'left':
        print('Left rockets')
        run_command('left', tdelay)
    elif key_press == 'right':
        print('right rockets')
        run_command('right', tdelay)
    elif key_press == 'up':
        print('up rockets')
        run_command('up', tdelay)
    elif key_press == 'down':
        print('down rockets')
        run_command('down', tdelay)


setup_usb()

#Enable USB to give supply upto 1.2A on model B+
if model_b_plus:
        os.system("gpio -g write 38 0")
        os.system("gpio -g mode 38 out")
        os.system("gpio -g write 38 1")

run_command("zero", 100)
stop()        

command = tk.Tk()
command.bind_all('<Key>', key_input)
command.mainloop()

You may be able to work it out, but there was a decent amount of cut and paste here. If you're confused, I would highly recommend watching the video for this part. Now, however, we have the ability to use the arrow keys to control our office cannon. While this can be useful, what's more interesting is that we can now see the crux of what it takes to move our robot and our cannon. From here, we can begin to make our robot autonomous, and build logic that will reasonably choose actions like moving, or shooting.

The next tutorial: Programming Autonomy - Robotics with Python Raspberry Pi and GoPiGo p.6