Ubuntu 12.4 Enable SSH Service

To install the openssh-server package run the command below in console.

sudo apt-get install openssh-server

Once installed, the SSH service should start automatically. If necessary, you can start the service using the command.

sudo service ssh start

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Z Axis drops after completing job

Symptoms
CNC machine Z Axis drops after completing job.

Relevant
Marlin 3D Printer Firmware running on Arduino Mega with RAMPS 1.4 shield. Controlled via Pronterface.

Procedure
The steppers motors will shut down DEFAULT_STEPPER_DEACTIVE_TIME seconds after the last move when DISABLE_INACTIVE_? is true. Individual axis can be disabled or DEFAULT_STEPPER_DEACTIVE_TIME can be set to zero to stop the axis from dropping.

  1. Open the firmware project
  2. Open file Configuration_adv.h
  3. Change the line from

    #define DEFAULT_STEPPER_DEACTIVE_TIME 120

    to

    #define DEFAULT_STEPPER_DEACTIVE_TIME 0
  4. Upload firmware project
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Reporting endstop status

Symptoms
CNC machine reports incorrect end stop trigger.

Relevant
Marlin 3D Printer Firmware running on Arduino Mega with RAMPS 1.4 shield. Controlled via Pronterface.

Procedure
The status of the end switches can be checked using the command M119. The procedure below explains how to check the status of the switches.

  1. Click the Connect button



  2. Enter the command M119 and then click the Send button. The command will display the status of each of the end switches.
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Simple Box G Code

Goal
The goal of this procedure is to draw a simple box 10x10mm.

Relevant
Marlin 3D Printer Firmware running on Arduino Mega with RAMPS 1.4 shield. Controlled via Pronterface.

Procedure
The procedure below is a simple gcode example that will show how to draw a simple 10mm box.

  1. Create a text file with the following code. In this example, we will call the text file box10x10mm.g

    G91
    G1 X10
    G1 Y10
    G1 X-10
    G1 Y-10
  2. Open Pronterface
  3. Click the Connect button, to connect to the device.

  4. Click the Home button, to home all of the axis.

  5. Click the Load File button.
  6. Select the file created in step 1.
  7. Click the Print button.
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Marlinfw Homing Direction

Symptoms
CNC machine homes in the wrong direction.

Relevant
Marlin 3D Printer Firmware running on Arduino Mega with RAMPS 1.4 shield.

Procedure
The direction of travel when homing is configured in the configuration.h using the settings X_HOME_DIR, Y_HOME_DIR and Z_HOME_DIR in the section ENDSTOP SETTINGS.
A value of -1 will set the homing direction towards the min end stop. A value of 1 will set the homing direction to the max end stop.

In the example below the homing direction for the z axis will be changed to home towards the max end stop.









The Z home value was -1 and has been changed to 1.


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Stepper Motor Control Service

Today I have been busy developing a stepper motor service class. The service class will allow the Team Seaford robot to play crazy golf.




import RPi.GPIO as GPIO
import time

class ServiceStepMotor:

  PinPhase1 = 14
  PinPhase2 = 15
  PinPhase3 = 17
  PinPhase4 = 16
  
  Steps = [
  [1,0,0,0],
  [1,1,0,0],
  [0,1,0,0],
  [0,1,1,0],
  [0,0,1,0],
  [0,0,1,1],
  [0,0,0,1],
  [1,0,0,1]
  ]

  StepIndex = 0
  
  MotorOnTime = 0.05  
  
  ## Constructor
  # @param self Class pointer
  def __init__(self):
    GPIO.setmode(GPIO.BCM)
    GPIO.setwarnings(False)
    
    self.SetPinToOutput(self.PinPhase1)
    self.SetPinToOutput(self.PinPhase2)
    self.SetPinToOutput(self.PinPhase3)
    self.SetPinToOutput(self.PinPhase4)
    pass

  ## Change pin type to output
  # @param self Class pointer
  # @param pin Pin Number  
  def SetPinToOutput(self, pin):
    GPIO.setup(pin,GPIO.OUT)
    self.Off(pin)
    pass
  
  ## Turn output pin On
  # @param self Class pointer
  # @param pin Pin Number  
  def On(self, pin):
    print "On="+str(pin)
    GPIO.output(pin,1)
    pass

  ## Turn output pin off
  # @param self Class pointer
  # @param pin Pin Number
  def Off(self, pin):
    GPIO.output(pin, 0)
    pass
  
  ## Change the output state of a pin
  # @param self Class pointer
  # @param PinNumber GPIO pin number
  # @param PinValue The new value for the GPIO pin  
  def ChangeOuput(self, PinNumber, PinValue):
    GPIO.output(PinNumber, PinValue)  
    pass
  
  ## Move stepper motor
  # @param self Class Pointer
  # @param Direction 1 = Forwards, 0 = Backwards
  def Step(self, direction):
    
    # Increment / decrement step count based on direction
    if (direction):
      # forward
      self.StepIndex += 1
    else:
      # backwards
      self.StepIndex -= 1
    
    # Check if we have passed the end of the steps list  
    if (self.StepIndex >= len(self.Steps)):
      self.StepIndex = 0
    
    # Check if we have reached the start of the steps list
    if (self.StepIndex < 0):
      self.StepIndex = len(self.Steps) - 1
      
    # Set output pin states
    print "StepIndex=" + str(self.StepIndex)
    phase = self.Steps[self.StepIndex]
    self.ChangeOuput(self.PinPhase1, phase[0])
    self.ChangeOuput(self.PinPhase2, phase[1])
    self.ChangeOuput(self.PinPhase3, phase[2])
    self.ChangeOuput(self.PinPhase4, phase[3])
    #for i in range(len(phase)):
    #  self.On(phase[i])
    
    # Delay while motor turns
    time.sleep(self.MotorOnTime)
    pass

The example code below shows how to use the stepper motor service class.

import ServiceStepMotor
sm = ServiceStepMotor.ServiceStepMotor()

print"Start"

print "Step forwards 10 steps"
for i in range(10):
  print "Step forward " + str(i)
  sm.Step(True)
  
print "Step backwards 10 steps"
for i in range(10):
  print "Step backward " + str(i)
  sm.Step(False)
  
print "Finish" 
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Pairing PS3 Controller with Raspberry Pi

We used WIFI to control our 2015 Pi Wars robot. Using WIFI was a big mistake. On the day of the competition, there was too much interference and lag. We have learnt from our mistakes. This time we will be using Bluetooth.

We have connected a USB Bluetooth dongle to the Raspberry Pi and using the instructions below connected a Sony Playstation Six Axis Controller.

  • Using micro usb cable plug in the PS3 controller into the raspberry pi
  • Enter the command sudo ./sixpair
  • Disconnect USB cable from PS3 controller
  • Enter the command bluetoothctl
  • Enter the command devices
  • Enter the command agenton
  • Enter the command trust followed by the MAC address of the controller. In my case the MAC address is 00:06:F5:C4:01:3b.
    trust 00:06:F5:C4:01:3b
  • Disconnect the usb cable
  • Press the PS button the top of the controller
  • Confirm the new input device has been succesffully added. Enter the command sudo ls /dev/input you should see JS0 has been added to the list of input devices
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Moving Forwards


Our robot is alive and moving. At the heart of the Team Seaford robot control is the ServiceIo class. The ServiceIo class is responsible for controlling the four drive motors. Each motor is connected to a H bridge motor controller. The H bridge controllers require two inputs per motor. The inputs control the direction of travel.

import RPi.GPIO as GPIO
import time

class ServiceIo:
  MotorOnTime = 0.01
  
  # GPIO Pin Numbers
  PinDriveFrontLeftForward = 5    # flf
  PinDriveFrontLeftBackward = 13  # flb
  PinDriveFrontRightForward = 11  # frf
  PinDriveFrontRightBackward = 12 # frb
  PinDriveBackLeftForward = 9     # blf
  PinDriveBackLeftBackward = 10   # blb
  PinDriveBackRightForward = 7    # brf
  PinDriveBackRightBackward = 8   # brb

  ## Constructor
  # @param self Class pointer
  def __init__(self):
    GPIO.setmode(GPIO.BCM)
    GPIO.setwarnings(False)
    
    self.SetPinToOutput(self.PinDriveFrontLeftForward)
    self.SetPinToOutput(self.PinDriveFrontLeftBackward)
    self.SetPinToOutput(self.PinDriveFrontRightForward)
    self.SetPinToOutput(self.PinDriveFrontRightBackward)
    self.SetPinToOutput(self.PinDriveBackLeftForward)
    self.SetPinToOutput(self.PinDriveBackLeftBackward)
    self.SetPinToOutput(self.PinDriveBackRightForward)
    self.SetPinToOutput(self.PinDriveBackRightBackward)
    pass
  
  ## Change pin type to output
  # @param self Class pointer
  # @param pin Pin Number  
  def SetPinToOutput(self, pin):
    GPIO.setup(pin,GPIO.OUT)
    self.Off(pin)
    pass
  
  ## Turn output pin On
  # @param self Class pointer
  # @param pin Pin Number  
  def On(self, pin):
    print "On="+str(pin)
    GPIO.output(pin,1)
    pass

  ## Turn output pin off
  # @param self Class pointer
  # @param pin Pin Number
  def Off(self, pin):
    GPIO.output(pin, 0)
    pass
  
  ## Stop all drive motors
  # @param self Class pointer
  def DriveStop(self):
    self.Off(self.PinDriveFrontLeftForward) 
    self.Off(self.PinDriveFrontLeftBackward)
    self.Off(self.PinDriveFrontRightForward)
    self.Off(self.PinDriveFrontRightBackward)
    self.Off(self.PinDriveBackLeftForward)
    self.Off(self.PinDriveBackLeftBackward)
    self.Off(self.PinDriveBackRightForward)
    self.Off(self.PinDriveBackRightBackward) 
    pass
  
  ## Drive Forward
  # @param self Class pointer
  def DriveForward(self):
    self.On(self.PinDriveFrontLeftForward)
    self.On(self.PinDriveFrontRightForward)
    self.On(self.PinDriveBackLeftForward)
    self.On(self.PinDriveBackRightForward)
    self.Off(self.PinDriveFrontLeftBackward)
    self.Off(self.PinDriveFrontRightBackward)
    self.Off(self.PinDriveBackLeftBackward)
    self.Off(self.PinDriveBackRightBackward)
    time.sleep(self.MotorOnTime)
    pass

  ## Drive Backward
  # @param self Class pointer
  def DriveBackward(self):
    self.On(self.PinDriveFrontLeftBackward)
    self.On(self.PinDriveFrontRightBackward)
    self.On(self.PinDriveBackLeftBackward)
    self.On(self.PinDriveBackRightBackward)
    self.Off(self.PinDriveFrontLeftForward)
    self.Off(self.PinDriveFrontRightForward)
    self.Off(self.PinDriveBackLeftForward)
    self.Off(self.PinDriveBackRightForward)
    time.sleep(self.MotorOnTime)
    pass
    
  ## Drive Left
  # @param self Class pointer
  def DriveLeft(self):
    self.On(self.PinDriveFrontLeftForward)
    self.Off(self.PinDriveFrontLeftBackward)
    self.On(self.PinDriveBackLeftForward)
    self.Off(self.PinDriveBackLeftBackward)
    self.On(self.PinDriveFrontRightBackward)
    self.Off(self.PinDriveFrontRightForward)
    self.On(self.PinDriveBackRightBackward)
    self.Off(self.PinDriveBackRightForward)
    time.sleep(self.MotorOnTime)
    pass
      
  ## Drive Right
  # @param self Class pointer
  def DriveRight(self):
    self.On(self.PinDriveFrontRightForward)
    self.Off(self.PinDriveFrontRightBackward)
    self.On(self.PinDriveBackRightForward)
    self.Off(self.PinDriveBackRightBackward)
    self.On(self.PinDriveFrontLeftBackward)
    self.Off(self.PinDriveFrontLeftForward)
    self.On(self.PinDriveBackLeftBackward)
    self.Off(self.PinDriveBackLeftForward)
    time.sleep(self.MotorOnTime)
    pass

The following code show how to use the ServiceIo within a simple program, which responds to user input from the keyboard.

import ServiceIo
import time

io = ServiceIo.ServiceIo()
io.DriveStop()


while True:
  mode = raw_input('Direction (f,b,l,r:')
  if (mode == 'f'):
    io.DriveForward()

  if(mode == 'b'):
    io.DriveBackward()

  if(mode=='l'):
    io.DriveLeft()

  if(mode=='r'):
    io.DriveRight()

  time.sleep(2)
  print("off")
  io.DriveStop()
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Configuring a Static IP Address on the Raspberry Pi

A static IP address will ensure that the Raspberry Pi will always have the same IP address. Without a static IP address the DHCP service on your router will randomly assign IP addresses from its IP range. A fixed IP address will make it easier to remotely connect to the Raspberry Pi.

In this example, the IP address for the Raspberry Pi will be set to 192.168.0.17.

  • Edit the interfaces file by entering the following command at the terminal.

    <
    >sudo nano /etc/network/interfaces
  • Change the eth0 settings to
    iface wlan0 inet static
    address 192.168.0.17
    netmask 255.255.255.0
    gateway 192.168.0.1
    broadcast 192.168.0.255
  • Press control + o to save
  • reboot by entering the command
    sudo shutdown -r now
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Preparing for Battle

This year Team Seaford will be competing in the non-destructive robot competition Pi Wars 2017, where robot controlled by Raspberry Pi’s will compete in a range of robotics challenges.

The brains for this years robot will be the Raspberry Pi Zero that we won in Pi Wars 2015.

Please, follow our progress as we build our robot.

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