I was wondering if it wouldn't be possible to use B4J to program the Lego Mindstorms EV3 Brick for some time. So, last week I finally spend a couple of evenings looking into it. And yes, B4J goes Robotics! It uses a modified LeJOS Firmware (I upgraded it to support Java 1.8).
Next I wrote a B4J wrapper for the basics like motors, sensors etc. This project is a hobby project and may grow and become public in the future. But I just wanted to share this first (badly directed) video
What happens in the video:
1. I uploaded the B4J created .jar file to the brick via ssh and I'm ready to start it.
2. After some time, it runs (on the brick shows a disclamer and waits for a key)
3. I disconnect the brick, put it on the ground and press a button on the brick
4. I programmed it if the IR sensor sees a wall, it turns away, else it keeps going
Fun fact is you can use b4j-bridge.jar too on the brick. This is handy as debugging a Brick is a b*tch! You must have a lot of patience and prepared to restart your brick A LOT. This is not a B4J limitation, just to say how unstable programming a Brick is in general.
Coding is straight forward in B4J (this is all the code used, including turning if it is about to hit a wall):
B4X:
Sub Process_Globals
Private StartTimer As Timer
Public EV3 As ABLegoEV3
Public LeftMotor As ABLLargeRegulatedMotor
Public RightMotor As ABLLargeRegulatedMotor
Public Sensor As ABLIRSensor
Public sp As ABLSensorMode
Public control As Int = 0
Public distance As Int = 255
End Sub
Sub AppStart (Args() As String)
LeftMotor.Initialize("B")
RightMotor.Initialize("C")
LeftMotor.ResetTachoCount
RightMotor.resetTachoCount
LeftMotor.rotateTo(0)
RightMotor.rotateTo(0)
LeftMotor.Speed = 400
RightMotor.Speed = 400
LeftMotor.Acceleration = 800
RightMotor.Acceleration = 800
Log("starting sensor")
Sensor.Initialize("S4")
sp = Sensor.DistanceMode
IntroMessage
StartTimer.Initialize("StartTimer", 100)
StartTimer.Enabled = True
StartMessageLoop
End Sub
Sub StartTimer_Tick
' read the sensor
Dim sample(sp.sampleSize) As Float
control = Sensor.getRemoteCommand(0)
sp.fetchSample(sample, 0)
distance = sample(0)
Log("Control: " & control & " Distance: " & distance)
If distance < 70 Then
Log("A wall!")
EV3.Button.LEDPattern(2)
LeftMotor.rotate2(-180, True) ' start Motor.B rotating backward
RightMotor.rotate(-180) ' rotate C farther To make the turn
If Bit.And(DateTime.Now, 1) <> 0 Then
LeftMotor.rotate2(-180, True) ' start Motor.B rotating backward
RightMotor.rotate(180) ' rotate C farther To make the turn
Else
RightMotor.rotate2(-180, True) ' start Motor.B rotating backward
LeftMotor.rotate(180) ' rotate C farther To make the turn
End If
Else
Log("Let's walk")
EV3.Button.LEDPattern(1)
LeftMotor.Speed = 400
RightMotor.Speed = 400
LeftMotor.Backward ' my motors are installed inverted on this robot
RightMotor.Backward
End If
End Sub
Sub IntroMessage()
Dim g As ABLGraphicsLCD = EV3.GraphicsLCD
g.clear
g.drawString("Bumper Car Demo", 5, 0, 0)
g.Font = g.Font.SmallFont
g.drawString("Demonstration of the Behavior", 2, 20, 0)
g.drawString("subsumption classes. Requires", 2, 30, 0)
g.drawString("a wheeled vehicle with two", 2, 40, 0)
g.drawString("independently controlled", 2, 50, 0)
g.drawString("motors connected to motor", 2, 60, 0)
g.drawString("ports B and C, and an", 2, 70, 0)
g.drawString("infrared sensor connected", 2, 80, 0)
g.drawString("to port 4.", 2, 90, 0)
' Quit GUI button:
g.Font = g.Font.SmallFont
Dim y_quit As Int = 100
Dim width_quit As Int = 45
Dim height_quit As Int = width_quit/2
Dim arc_diam As Int = 6
g.drawString("QUIT", 9, y_quit+7, 0)
g.drawLine(0, y_quit, 45, y_quit) ' top line
g.drawLine(0, y_quit, 0, y_quit+height_quit-arc_diam/2) ' left line
g.drawLine(width_quit, y_quit, width_quit, y_quit+height_quit/2) ' right line
g.drawLine(0+arc_diam/2, y_quit+height_quit, width_quit-10, y_quit+height_quit) ' bottom line
g.drawLine(width_quit-10, y_quit+height_quit, width_quit, y_quit+height_quit/2) ' diagonal
g.drawArc(0, y_quit+height_quit-arc_diam, arc_diam, arc_diam, 180, 90)
' Enter GUI button:
g.fillRect(width_quit+10, y_quit, height_quit, height_quit)
g.drawString2("GO", width_quit+15, y_quit+7, 0,True)
EV3.Button.WaitForAnyPress
If (EV3.Button.ESCAPE.isDown()) Then
ExitApplication2(0)
End If
g.clear
End SubAs I said, this is just for fun. No idea how far I will take this.
Cheers,
Alwaysbusy
Last edited:
