PHY 235 Robotics Workshop
Day 8
IO, Multi-tasking
Sample Start Program
Team Projects
IO Planning
• When planning the design of your robot, keep in
mind how you will use the IO pins. You will need
at least:
• 4 pins for Lego Motor control
• 4 pins for IR Beacon (discussed tomorrow)
• 1 pin for bottom photo-resistor to sense start
light
• This makes 9 pins that are necessary, leaving 7
pins for your use.
IO Planning
• Possible uses for remaining 7 pins:
• DC Motor – This will require another motor controller
board and 2-4 pins (1-2 motors)
• Servo Motors – This will require 1 signal pin for each
servo
• IR distance/proximity sensor – 1 pin
• Other photo-resistors – 1 pin
• Bump (Whisker, Switch) sensor – 1 pin
• Ping – 1 pin
• LCD Display (This uses up to 4 of your IO pins)
Multi-Tasking
• Multi-tasking refers to the ability to create a
program that will carry out more than one
process at the same time.
• Zbasic allows for multi-tasking. If there is
more than one task, then a task scheduler
switches back and forth between tasks every
CPU time tic (about 1.95 micro-sec’s)
• For the user, this gives the appearance of the
two tasks happening simultaneously.
Multi-Tasking
• The subroutine Main() is a single task. To
create another task we need to do two things:
• Reserve space for the new task on the Task
Stack. The task stack is a portion of RAM set aside
exclusively for the new task.
• Create the task by writing
CallTask “NameOfTask” , taskStack
Multi-Tasking - Example
• Here is an example:
Dim taskStack(1 to 80) as Byte
Sub Main()
CallTask "MyTask", taskStack
Do
Debug.Print "Hello from Main"
Call Delay(1.0)
Loop
End Sub
Sub MyTask()
Do
Debug.Print "Hello from MyTask"
Call Delay(2.0)
Loop
End Sub
Multi-Tasking - Example
• From the Zbasic Reference:
“This program has two tasks: Main and MyTask. The Main
task is created automatically and its task stack is
automatically allocated all of the remaining User RAM after
explicitly defined variables are allocated. In contrast,
additional tasks such as MyTask have to be explicitly
invoked using the CallTask statement and each task’s stack
must also be explicitly allocated, for example by defining
a Byte array as shown above. A task is said to be “active” if
it has been invoked by CallTask and has not yet
terminated. Both of the tasks above never terminate so
they are always active. “
RoboPong Start Program Template
• For our contest, we will need to have the robot
keep track of time and shut itself off at the end
of 60 seconds.
• The best way to do this is to create a second
task that will just sleep for 60 seconds and then
shut things down.
• The code on the next slide is a prototype you
can use for developing your program.
RoboPong Start Program Template
Dim taskStack(1 to 80) as Byte
' Memory allocation for 2nd task
Dim continueFlag as Boolean = true
' Motor IO pins
const p0 as byte = 5
const p1 as byte = 6
const p2 as byte = 7
const p3 as byte = 8
' Data for Bottom Photoresistor to read start light
const p15 as byte = 20
'IO pin for bottom light sensor
const startLightThreshold as integer = 300
Dim bottomLightVal as Integer = 1 ' where we store sensor value
RoboPong Start Program Template
Sub Main()
' Wait for start light signal
while bottomLightVal < startLightThreshold
' read photoresistor value
bottomLightVal = GetADC(p15)
wend
' Start the timing task
CallTask "StopAfter60Seconds", taskStack
' Determine which side you are on - white or black
Call SetSideForMatch()
' Main loop - read sensors and take action
Do until continueFlag = false
Call GetAllSensorVals()
Call TakeAction()
Loop
End Sub
RoboPong Start Program Template
Sub StopAfter60Seconds()
'Sleep for 60 seconds
Call sleep(60.0)
' Lock this task so no other tasks can execute
Call LockTask()
' Set the continueFlag just in case some other task
' is still executing
continueFlag = false
' Turn off all motors
call ShutDownMotors()
' Exit the Main() task - should exit the program
call ExitTask()
End Sub
RoboPong Start Program Template
Sub GetAllSensorVals()
End Sub
Sub TakeAction()
' Motors rotate one direction
call putpin(p0, 1)
call putpin(p1, 0)
call putpin(p2, 1)
call putpin(p3, 0)
call delay(0.5)
' Motors rotate other direction
call putpin(p0, 0)
call putpin(p1, 1)
call putpin(p2, 0)
call putpin(p3, 1)
call delay(0.5)
End Sub
Sub ShutDownMotors()
' Stop both Lego Motors
call Putpin(p0, 0)
call Putpin(p1, 0)
call Putpin(p2, 0)
call Putpin(p3, 0)
' Stop any other DC motors or Servos
End Sub
Sub SetSideForMatch()
End Sub
Team Projects
• In addition to preparing for the RoboPong contest,
each team will research a specific advanced sensor
(or interface device) to the Boe-bot CPU.
• The sensors are in three categories:
I. Basic Sensor – Complex Usage
• Break Beam Sensor (See F. Martin Text)
• Shaft Encoding (See F. Martin Text)
• Sharp GP2D02 Distance sensor (Optical)
(See F. Martin Text)
• Parallax 2-axis Joystick
(Go to parallax.com for doc’s and examples
Team Projects
II. Sensor Using Synchronous Serial IO (- Hvidsten Slides)
• Honeywell HMC6352 Compass
• Hitachi H48C Tri-Axis Accelerometer
• Parallax ColorPal Color Sensor
• Parallax Passive Infrared Motion Sensor
• DS1620 Digital Thermometer
(Go to parallax.com for doc’s and examples on these)
III. Interface to Winbond audio board
(I have some ref’s for this project)
Team Projects
• The projects in group II require the use of
Synchronous-Serial Interfacing. I have slides from a
previous course on this topic.
• The most challenging project is the one in group III. I
will assist any group who wishes to tackle this one.
• The 6 teams will work on 6 different projects. Teams
will be given the opportunity to choose a project type
based on a random selection of team order.
Team Project Requirements
• Each team will do research on their project, develop code,
and produce two products:
1. A team presentation to the class on their project. The
presentation should include:
a. Background and theory on how sensor (device)
works.
b. Sample code to show how to use sensor/device.
c. Demo of Robot (Lego or Boe-bot) using the device.
2. A written AppNote. This is a 2-3 page document which
explains the sensor, shows breadboard/schematic and
shows sample code. An example of such an AppNote is
included on the Documents page of the course web site.
Team Project Timeline
Wed, January 12 – Tuesday, January 18
Teams work on project
Wednesday-Friday, January 19-21
Team Presentations (2 per day)