YetiBorg - The Formula Pi series racer

This is our web based interface for controlling your YetiBorg from a phone or browser.

This example provides web-based access to a YetiBorg using a web browser on both phones and desktops.
The interface streams images from the Raspberry Pi camera, movement can be controlled from the buttons.

Getting ready

Before using this script you should make sure your YetiBorg is working with the standard examples.

You will need to also perform the optional camera setup so the script can stream images.
You will not need the option joystick setup for this example.

You will probably want to use a WiFi dongle for the best results.
Make sure your WiFi is working and connected to you router before running the scripts.

Downloading the code from GitHub

In a terminal run the following commands:

cd ~
git clone https://github.com/piborg/diddyborg-web.git

Alternatively you can download the yetiWeb.py script file as text here.

Running the code

This is easiest done via SSH over the WiFi.

First find out what your IP address is using the ifconfig command.
It should be 4 numbers separated by dots, e.g. 192.168.0.198
We will need this to access the controls, so make a note of it.

Next run the script using:
sudo ~/diddyborg-web/yetiWeb.py

Wait for the script to load, when it is ready it should say:
Press CTRL+C to terminate the web-server

Controlling your YetiBorg

Load your web browser on your phone or desktop.
Once loaded enter your IP address in the address bar

You should be presented with the camera image, some text, some buttons, and a slider.

To move click a movement button, such as Forward.
To stop moving click the Stop button.

To change the speed, drag the slider before clicking a movement button.
Left is slower, right is faster.

The last motor settings are displayed below the image.

Additional settings

There are some settings towards the top of the script which may be changed to adjust the behaviour of the interface:

webPort - Sets the port number, 80 is the default port web browsers will try
imageWidth - The width of the captured camera image, higher will need more network bandwidth
imageHeight - The height of the captured camera image, higher will need more network bandwidth
frameRate - The number of images taken from the camera each second by the Raspberry Pi
displayRate - The number of times per second the web browser will refresh the camera image
photoDirectory - The directory that photos are saved to when taken

Auto start at boot

To get the web interface to load on its own do the following:

Open the Cron table using crontab -e
Add a cron job to the bottom of the file using the following line:
@reboot sudo /home/pi/diddyborg-web/yetiWeb.py
Save the file
Close the file

The cron table should now auto-run the script when the Raspberry Pi boots up.

Going further

This is just a simple example of how a web interface can be made using Python on the Raspberry Pi to control a robot.

We think sharing software is awesome, so we encourage others to extend and/or improve on this script to make it do even more :)
To assist that we have uploaded the files as a self-contained project on GitHub:
https://github.com/piborg/diddyborg-web

The source code

#!/usr/bin/env python
# coding: Latin-1

# Creates a web-page interface for YetiBorg

# Import library functions we need
import ZeroBorg
import time
import sys
import threading
import SocketServer
import picamera
import picamera.array
import cv2
import datetime

# Settings for the web-page
webPort = 80                            # Port number for the web-page, 80 is what web-pages normally use
imageWidth = 240                        # Width of the captured image in pixels
imageHeight = 180                       # Height of the captured image in pixels
frameRate = 10                          # Number of images to capture per second
displayRate = 2                         # Number of images to request per second
photoDirectory = '/home/pi'             # Directory to save photos to

# Global values
global ZB
global lastFrame
global lockFrame
global camera
global processor
global running
global watchdog
running = True

# Setup the ZeroBorg
ZB = ZeroBorg.ZeroBorg()
#ZB.i2cAddress = 0x44                  # Uncomment and change the value if you have changed the board address
ZB.Init()
if not ZB.foundChip:
    boards = ZeroBorg.ScanForZeroBorg()
    if len(boards) == 0:
        print 'No ZeroBorg found, check you are attached :)'
    else:
        print 'No ZeroBorg at address %02X, but we did find boards:' % (ZB.i2cAddress)
        for board in boards:
            print '    %02X (%d)' % (board, board)
        print 'If you need to change the IÂ²C address change the setup line so it is correct, e.g.'
        print 'ZB.i2cAddress = 0x%02X' % (boards[0])
    sys.exit()
#ZB.SetEpoIgnore(True)                 # Uncomment to disable EPO latch, needed if you do not have a switch / jumper
ZB.SetCommsFailsafe(False)
ZB.ResetEpo()
ZB.SetLed(False)

# Power settings
voltageIn = 8.4                         # Total battery voltage to the ZeroBorg (change to 9V if using a non-rechargeable battery)
voltageOut = 6.0                        # Maximum motor voltage

# Setup the power limits
if voltageOut > voltageIn:
    maxPower = 1.0
else:
    maxPower = voltageOut / float(voltageIn)

# Timeout thread
class Watchdog(threading.Thread):
    def __init__(self):
        super(Watchdog, self).__init__()
        self.event = threading.Event()
        self.terminated = False
        self.start()
        self.timestamp = time.time()

    def run(self):
        timedOut = True
        # This method runs in a separate thread
        while not self.terminated:
            # Wait for a network event to be flagged for up to one second
            if timedOut:
                if self.event.wait(1):
                    # Connection
                    print 'Reconnected...'
                    timedOut = False
                    self.event.clear()
            else:
                if self.event.wait(1):
                    self.event.clear()
                else:
                    # Timed out
                    print 'Timed out...'
                    timedOut = True
                    ZB.MotorsOff()

# Image stream processing thread
class StreamProcessor(threading.Thread):
    def __init__(self):
        super(StreamProcessor, self).__init__()
        self.stream = picamera.array.PiRGBArray(camera)
        self.event = threading.Event()
        self.terminated = False
        self.start()
        self.begin = 0

    def run(self):
        global lastFrame
        global lockFrame
        # This method runs in a separate thread
        while not self.terminated:
            # Wait for an image to be written to the stream
            if self.event.wait(1):
                try:
                    # Read the image and save globally
                    self.stream.seek(0)
                    flippedArray = cv2.flip(self.stream.array, -1) # Flips X and Y
                    retval, thisFrame = cv2.imencode('.jpg', flippedArray)
                    del flippedArray
                    lockFrame.acquire()
                    lastFrame = thisFrame
                    lockFrame.release()
                finally:
                    # Reset the stream and event
                    self.stream.seek(0)
                    self.stream.truncate()
                    self.event.clear()

# Image capture thread
class ImageCapture(threading.Thread):
    def __init__(self):
        super(ImageCapture, self).__init__()
        self.start()

    def run(self):
        global camera
        global processor
        print 'Start the stream using the video port'
        camera.capture_sequence(self.TriggerStream(), format='bgr', use_video_port=True)
        print 'Terminating camera processing...'
        processor.terminated = True
        processor.join()
        print 'Processing terminated.'

    # Stream delegation loop
    def TriggerStream(self):
        global running
        while running:
            if processor.event.is_set():
                time.sleep(0.01)
            else:
                yield processor.stream
                processor.event.set()

# Class used to implement the web server
class WebServer(SocketServer.BaseRequestHandler):
    def handle(self):
        global ZB
        global lastFrame
        global watchdog
        # Get the HTTP request data
        reqData = self.request.recv(1024).strip()
        reqData = reqData.split('\n')
        # Get the URL requested
        getPath = ''
        for line in reqData:
            if line.startswith('GET'):
                parts = line.split(' ')
                getPath = parts[1]
                break
        watchdog.event.set()
        if getPath.startswith('/cam.jpg'):
            # Camera snapshot
            lockFrame.acquire()
            sendFrame = lastFrame
            lockFrame.release()
            if sendFrame != None:
                self.send(sendFrame.tostring())
        elif getPath.startswith('/off'):
            # Turn the drives off
            httpText = '<html><body><center>'
            httpText += 'Speeds: 0 %, 0 %'
            httpText += '</center></body></html>'
            self.send(httpText)
            ZB.MotorsOff()
        elif getPath.startswith('/set/'):
            # Motor power setting: /set/driveLeft/driveRight
            parts = getPath.split('/')
            # Get the power levels
            if len(parts) >= 4:
                try:
                    driveLeft = float(parts[2])
                    driveRight = float(parts[3])
                except:
                    # Bad values
                    driveRight = 0.0
                    driveLeft = 0.0
            else:
                # Bad request
                driveRight = 0.0
                driveLeft = 0.0
            # Ensure settings are within limits
            if driveRight < -1:
                driveRight = -1
            elif driveRight > 1:
                driveRight = 1
            if driveLeft < -1:
                driveLeft = -1
            elif driveLeft > 1:
                driveLeft = 1
            # Report the current settings
            percentLeft = driveLeft * 100.0;
            percentRight = driveRight * 100.0;
            httpText = '<html><body><center>'
            httpText += 'Speeds: %.0f %%, %.0f %%' % (percentLeft, percentRight)
            httpText += '</center></body></html>'
            self.send(httpText)
            # Set the outputs
            driveLeft *= maxPower
            driveRight *= maxPower
            ZB.SetMotor1(-driveRight * maxPower) # Front right
            ZB.SetMotor2(-driveLeft  * maxPower) # Front left
            ZB.SetMotor3(-driveLeft  * maxPower) # Rear left
            ZB.SetMotor4(-driveRight * maxPower) # Rear right
        elif getPath.startswith('/photo'):
            # Save camera photo
            lockFrame.acquire()
            captureFrame = lastFrame
            lockFrame.release()
            httpText = '<html><body><center>'
            if captureFrame != None:
                photoName = '%s/Photo %s.jpg' % (photoDirectory, datetime.datetime.utcnow())
                try:
                    photoFile = open(photoName, 'wb')
                    photoFile.write(captureFrame)
                    photoFile.close()
                    httpText += 'Photo saved to %s' % (photoName)
                except:
                    httpText += 'Failed to take photo!'
            else:
                httpText += 'Failed to take photo!'
            httpText += '</center></body></html>'
            self.send(httpText)
        elif getPath == '/':
            # Main page, click buttons to move and to stop
            httpText = '<html>\n'
            httpText += '<head>\n'
            httpText += '<script language="JavaScript"><!--\n'
            httpText += 'function Drive(left, right) {\n'
            httpText += ' var iframe = document.getElementById("setDrive");\n'
            httpText += ' var slider = document.getElementById("speed");\n'
            httpText += ' left *= speed.value / 100.0;'
            httpText += ' right *= speed.value / 100.0;'
            httpText += ' iframe.src = "/set/" + left + "/" + right;\n'
            httpText += '}\n'
            httpText += 'function Off() {\n'
            httpText += ' var iframe = document.getElementById("setDrive");\n'
            httpText += ' iframe.src = "/off";\n'
            httpText += '}\n'
            httpText += 'function Photo() {\n'
            httpText += ' var iframe = document.getElementById("setDrive");\n'
            httpText += ' iframe.src = "/photo";\n'
            httpText += '}\n'
            httpText += '//--></script>\n'
            httpText += '</head>\n'
            httpText += '<body>\n'
            httpText += '<iframe src="/stream" width="100%" height="500" frameborder="0"></iframe>\n'
            httpText += '<iframe id="setDrive" src="/off" width="100%" height="50" frameborder="0"></iframe>\n'
            httpText += '<center>\n'
            httpText += '<button onclick="Drive(-1,1)" style="width:200px;height:100px;"><b>Spin Left</b></button>\n'
            httpText += '<button onclick="Drive(1,1)" style="width:200px;height:100px;"><b>Forward</b></button>\n'
            httpText += '<button onclick="Drive(1,-1)" style="width:200px;height:100px;"><b>Spin Right</b></button>\n'
            httpText += '<br /><br />\n'
            httpText += '<button onclick="Drive(0,1)" style="width:200px;height:100px;"><b>Turn Left</b></button>\n'
            httpText += '<button onclick="Drive(-1,-1)" style="width:200px;height:100px;"><b>Reverse</b></button>\n'
            httpText += '<button onclick="Drive(1,0)" style="width:200px;height:100px;"><b>Turn Right</b></button>\n'
            httpText += '<br /><br />\n'
            httpText += '<button onclick="Off()" style="width:200px;height:100px;"><b>Stop</b></button>\n'
            httpText += '<br /><br />\n'
            httpText += '<button onclick="Photo()" style="width:200px;height:100px;"><b>Save Photo</b></button>\n'
            httpText += '<br /><br />\n'
            httpText += '<input id="speed" type="range" min="0" max="100" value="100" style="width:600px" />\n'
            httpText += '</center>\n'
            httpText += '</body>\n'
            httpText += '</html>\n'
            self.send(httpText)
        elif getPath == '/hold':
            # Alternate page, hold buttons to move (does not work with all devices)
            httpText = '<html>\n'
            httpText += '<head>\n'
            httpText += '<script language="JavaScript"><!--\n'
            httpText += 'function Drive(left, right) {\n'
            httpText += ' var iframe = document.getElementById("setDrive");\n'
            httpText += ' var slider = document.getElementById("speed");\n'
            httpText += ' left *= speed.value / 100.0;'
            httpText += ' right *= speed.value / 100.0;'
            httpText += ' iframe.src = "/set/" + left + "/" + right;\n'
            httpText += '}\n'
            httpText += 'function Off() {\n'
            httpText += ' var iframe = document.getElementById("setDrive");\n'
            httpText += ' iframe.src = "/off";\n'
            httpText += '}\n'
            httpText += 'function Photo() {\n'
            httpText += ' var iframe = document.getElementById("setDrive");\n'
            httpText += ' iframe.src = "/photo";\n'
            httpText += '}\n'
            httpText += '//--></script>\n'
            httpText += '</head>\n'
            httpText += '<body>\n'
            httpText += '<iframe src="/stream" width="100%" height="500" frameborder="0"></iframe>\n'
            httpText += '<iframe id="setDrive" src="/off" width="100%" height="50" frameborder="0"></iframe>\n'
            httpText += '<center>\n'
            httpText += '<button onmousedown="Drive(-1,1)" onmouseup="Off()" style="width:200px;height:100px;"><b>Spin Left</b></button>\n'
            httpText += '<button onmousedown="Drive(1,1)" onmouseup="Off()" style="width:200px;height:100px;"><b>Forward</b></button>\n'
            httpText += '<button onmousedown="Drive(1,-1)" onmouseup="Off()" style="width:200px;height:100px;"><b>Spin Right</b></button>\n'
            httpText += '<br /><br />\n'
            httpText += '<button onmousedown="Drive(0,1)" onmouseup="Off()" style="width:200px;height:100px;"><b>Turn Left</b></button>\n'
            httpText += '<button onmousedown="Drive(-1,-1)" onmouseup="Off()" style="width:200px;height:100px;"><b>Reverse</b></button>\n'
            httpText += '<button onmousedown="Drive(1,0)" onmouseup="Off()" style="width:200px;height:100px;"><b>Turn Right</b></button>\n'
            httpText += '<br /><br />\n'
            httpText += '<button onclick="Photo()" style="width:200px;height:100px;"><b>Save Photo</b></button>\n'
            httpText += '<br /><br />\n'
            httpText += '<input id="speed" type="range" min="0" max="100" value="100" style="width:600px" />\n'
            httpText += '</center>\n'
            httpText += '</body>\n'
            httpText += '</html>\n'
            self.send(httpText)
        elif getPath == '/stream':
            # Streaming frame, set a delayed refresh
            displayDelay = int(1000 / displayRate)
            httpText = '<html>\n'
            httpText += '<head>\n'
            httpText += '<script language="JavaScript"><!--\n'
            httpText += 'function refreshImage() {\n'
            httpText += ' if (!document.images) return;\n'
            httpText += ' document.images["rpicam"].src = "cam.jpg?" + Math.random();\n'
            httpText += ' setTimeout("refreshImage()", %d);\n' % (displayDelay)
            httpText += '}\n'
            httpText += '//--></script>\n'
            httpText += '</head>\n'
            httpText += '<body onLoad="setTimeout(\'refreshImage()\', %d)">\n' % (displayDelay)
            httpText += '<center><img src="/cam.jpg" style="width:640;height:480;" name="rpicam" /></center>\n'
            httpText += '</body>\n'
            httpText += '</html>\n'
            self.send(httpText)
        else:
            # Unexpected page
            self.send('Path : "%s"' % (getPath))

    def send(self, content):
        self.request.sendall('HTTP/1.0 200 OK\n\n%s' % (content))


# Create the image buffer frame
lastFrame = None
lockFrame = threading.Lock()

# Startup sequence
print 'Setup camera'
camera = picamera.PiCamera()
camera.resolution = (imageWidth, imageHeight)
camera.framerate = frameRate

print 'Setup the stream processing thread'
processor = StreamProcessor()

print 'Wait ...'
time.sleep(2)
captureThread = ImageCapture()

print 'Setup the watchdog'
watchdog = Watchdog()

# Run the web server until we are told to close
httpServer = SocketServer.TCPServer(("0.0.0.0", webPort), WebServer)
try:
    print 'Press CTRL+C to terminate the web-server'
    while running:
        httpServer.handle_request()
except KeyboardInterrupt:
    # CTRL+C exit
    print '\nUser shutdown'
finally:
    # Turn the motors off under all scenarios
    ZB.MotorsOff()
    print 'Motors off'
# Tell each thread to stop, and wait for them to end
running = False
captureThread.join()
processor.terminated = True
watchdog.terminated = True
processor.join()
watchdog.join()
del camera
ZB.SetLed(True)
print 'Web-server terminated.'

Main menu

YetiBorg - The Formula Pi series racer

Getting ready

Downloading the code from GitHub

Running the code

Controlling your YetiBorg

Additional settings

Auto start at boot

Going further

The source code

Latest Blog

A robot called BOB

Tags:

Main menu

You are here

YetiBorg - The Formula Pi series racer

Getting ready

Downloading the code from GitHub

Running the code

Controlling your YetiBorg

Additional settings

Auto start at boot

Going further

The source code

Latest Blog

A robot called BOB

Tags:

User login