Transcript Programming and Controls Workshop

Programming and Controls
Workshop – The Basics
Tom Barch
Agenda
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System Overview
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How the systems works – Controls Block Diagram
Robot Controller
Operator Interface
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Overview of the controls used and how they work
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Default Code Reference Guide – How an why to use
MPLAB and IFI Loader – How to install and use
Default Code – An overview
Downloading the Code to the Robot Controller
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Overview of the pneumatics system – Block Diagram
Controlling the pneumatics – Understanding the controls
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How to download and test using a real system
Controls
Programming
Pneumatic Controls
Hands On Demonstration
Robot Controller or RC
Operator Interface or OI
Tether Communications
Radio vs. Tether communication
 If the controllers ‘see’ a tether cable
connection, then they will communicate via
the tether port.
 If no tether connection exists, then they
will attempt to use the radio signal.
 Note: Connecting via radio at the
competition other than during a match is
not allowed and can be dangerous if
another teams operator interface controls
your robot.
Controls
 Understanding the controls will help to understand the
software variables and how the software is modifying
and outputting them to get the Robot to move.
 The joystick is read by the Operator Interface and is
transmitted to the Robot Controller. It usually drives
a pwm output which controls a Victor 883 or 884
speed controller. The speed controller maybe wired to
a drill motor.
 By pressing the joystick, we hope to control the speed
and direction of the motor to get the Robot to move.
 Lets start with the Joystick.
Joystick
 The joystick consists of two potentiometers mounted to a
stick that vary as the stick is moved along its axis.
 One potentiometer is mounted in the x axis or left –
right direction and the other is mounted in the y axis or
forward – backward direction.
 As the potentiometer moves from one extreme to the
other, the operator interface reads the voltage from 0 to
5 volts.
 This voltage is broken into an 8 byte variable that ranges
from 0 (0 volts) to 254 (5 volts).
 The variables in the software for the input ports on the
OI are pX_axis where x is port 1 to 4 and the axis is x, y,
or wheel. (example p1_y is port one, y axis or
forward/backward)
Joystick - continued
 Full forward in the
y axis will result in
p1_y = 254.
 When the joystick
is in the center,
p1_y = 127.
 Full backward
p1_y = 0.
Victor Speed Controller
 The input to the speed controller is a pulse width
modulated (pwm) signal that varies from a value of 0
to 254.
 In the software, these variables are labeled pwm01 –
pwm16 corresponding to the pwm input on the RC.
 Battery and ground is supplied to two input terminals
and the two output terminals can be wired to an
electrical load like a drill motor.
 At an input of 127, the two outputs which we will call
m+ and m- are at 0 volt difference
 As the pwm increases from 127 toward 254, the
voltage varies from a positive difference of 0 to 12
volts.
 As the pwm decreases from 127 towards 0, the voltage
varies from a negative difference of 0 to 12 volts.
Victor 883 or 884 speed controller
Joystick to Motor
 The joystick variable is the same as the variable
outputted to the pwm output to drive the motors
forward and reverse.
 In the default software, port one y axis is output
directly to pwm01 port:
pwm01 = p1_y;
 In the default software, port two y axis is output
directly to pwm02 port:
pwm02 = p2_y;
 The two of these make up the tank drive (two
joystick).
 The software also outputs joystick one x and y axis to
pwm ports 13 and 15 to get one joystick drive.
Joystick Switches
 Located on the joysticks are four switches that are read
by the computer as 0 or a 1. When the switch is closed,
then the variable is read as a one.
 These switch inputs for each one of the four input ports
on the OI are:
p1_sw_trig
p1_sw_top
p1_sw_aux1
p1_sw_aux2
Spike Controller
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The spike controller is a relay or electronic switch that will
drive two outputs based on the inputs.
The reason for two input and two outputs are to enable the
output to be driven positively or negatively to drive a small
motor forward or reverse.
When the inputs to the relay are driven both as 0, then the
outputs are both at 0 volts. One input is called Fwd and
one is called Rev. One output is m+ the other is m-.
If the Fwd input is a 1 and the Rev input is a zero, then the
m+ output will be 12volts and the m- output will be 0 volts.
The spike can be used to drive small motors, lights, air
compressor, or any other 12 volt electrical load. The
concern is the current draw which is much lower then the
speed controllers.
Spike Blue Controller
Spike Truth Table
 The truth table for the input to output is as
follows:
Spike alternative circuit
 The spike can also be used to drive two
different outputs in a on/off sequence.
 An example would be two solenoid valves.
Programming the Robot Controller
Robot Controller Code
 MPLAB IDE v7.20 is the C programming editor
and complier from Microchips used to edit and
compile the code.
 IFI Loader is a program that will download the
complied code into the robot.
 None of this is necessary if the default code is
used.
 If modifications are necessary (custom
functions are needed/variables need to change
slightly), the code will only need modifications
instead of a complete re-write.
Default Code Reference Guide
 Available from Innovation First website
http://www.ifirobotics.com/
(in the Robot Controller section at the bottom)
 Shows OI wiring/variables to RC
variables/output for the default code
functions.
 Contains the variable listing for modification
of default code.
FRC 2004 Default Code Reference Guide.pdf
Table of Contents
Joystick Function
Joystick plugged
into port 1
Y-Axis is forward
– backwards
(tank drive)
P1_y is the
variable used
in the software
to read this
function
RC PWM1 is the port
that the left side
victor should be
plugged into to make
port 1 the left joystick
for tank style drive
Single Joystick Drive
 Missing from default guide – It is on the
front cover but hard to read.
 Connect the right drive motors to PWM13
and/or PWM14 on the RC.
 Connect the left drive motors to PWM15
and/or PWM16 on the RC.
MPLAB Install
 Adobe PDF
document exists on
CD
 Has the defaults
and instructions for
installing MPLAB as
well as the IFI
loader.
 C-BOT_Install_129-2004.pdf
MPLAB and Default code
 After downloading the default code, place
the unzipped files in a directory, preferable
in c:\code\frccode.
 MPLAB and First recommends a simple
directory. My Documents is a complex
directory in Windows 2000 and Windows
XP.
 Saving an old revision and creating a new
one is done by copying the folder and
pasting to new director (i.e. copy
c:\code\frccode into a new directory
c:\code\frccode1 and so on).
Opening the default workspace
 Do not use the file open command. Use
the open workspace command.
User_routine.c
 Most of the code changes will be made in
the user_routine.c file
 Custom code should be placed in
Process_Data_From_Master_uP function at
/* Add your own code here */.
 The specific functions for most of the
inputs/outputs are in the Default_Routine
which is at the bottom of User_routine.c
 The variables can be modified in the default
routine, but make sure to use new revision
(directory) here so that changes can be
reversed.
C Programming
 C is a popular powerful language that
requires conciseness with a wealth of
operators.
 Teaching C in a one hour workshop would
be impossible.
 The next few slides are intended to help
understand some of the C language basics
in order to make minor modifications to the
default program.
C Language Basics
 C is a compiled language.
 The C compiler is a program that reads source code, which
is the C code written by a programmer, and produces an
executable or binary file that in a format that can be read
and executed (run) by a computer.
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The source file’s are a plain text file containing the text version
of the code written in correct syntax for the C complier.
The executable file consists of machine code, 1's and 0's that
are not meant to be understood or read by people, but only by
computers. This is the file that gets downloaded into the RC.
The compiler will make the executable file from the source
code and check for syntax errors. The complier does not
check for logic errors.
 The best way to learn anything is to jump right in, so let's
start by looking a simple C program.
C Program Structure
Code Comments
 Comments in C are done in one of two ways:
 /* Comments are placed between text markers and
can span multiple lines of text*/
 // Comments on one line only
 Most C programmers use the comment
markers /* text */
 Text should be green if the right markers are
used in MPLAB.
Relational Operators
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You may have noticed the == sign used in the if statement.
Unlike most other programming languages, the = is an
assignment operator. The double == is the equality operator.
== equal operator
5 == 4 FALSE or 5 == 5 TRUE
!= not equal
5 != 4 True or 5 != 5 FALSE
> greater than
5 > 4 TRUE or 5 > 5 FALSE
>= greater than or equal
5 >= 4 TRUE or 5 >= 5 TRUE
< less than
5 < 4 FALSE or 5 < 5 FALSE
<= less than or equal
5 <= 4 FALSE or 5 <= 5 TRUE
End of line markers
 Some of the code is ended with the
semicolon ;
pwm01 = p1_y;
 Braces mark the beginning as well as the
end of the body of a function.
If (p1_y == 127)
{
p1_x = 127;
}
Variables in C
 Valid names can consist of letters, numbers
and the underscore, but may not start with
a number. A variable name may not be a C
keyword such as if, for, else, or while.
Variable names are case sensitive. So, Age,
AGE, aGE and AgE could be names for
different variables, although this is not
recommended since it would probably
cause confusion and errors in your
programs.
Declaring Variables
 Variables are usually declared at the top of
the module or in a separate “header” file
which usually ends with .h file type.
 In the space before the variable or function
being declared, is the data type the
variable or function will return.
 A variable can be assigned a value in the
declaration statement.
 C provides built in data types for character,
float and integer data. A mechanism, using
the keyword typedef, exists for creating
user-defined types.
Data type - Integer
 Integer variables are used to store whole numbers.
 There are several keywords used to declare integer
variables, including int, short, long, unsigned short,
unsigned long. The difference deals with the number
of bytes used to store the variable in memory, long
vs. short, or whether negative and positive numbers
may be stored, signed vs. unsigned.
 Examples:
int count;
int number_of_students = 30;
Data types – floating decimal point
 Float variables are used to store floating point
numbers.
 Floating point numbers may contain both a whole and
fractional part, for example, 52.7 or 3.33333333.
 There are several keywords used to declare floating
point numbers in C including float, double and long
double. The difference here is the number of bytes
used to store the variable in memory. Double allows
larger values than float. Long double allows even
larger values.
 Examples:
float pwm23_new = 0.0;
double pwm23_new2 = 1234567.89;
Data types - Character
 Character variables are used to store
character values.
 Character type is actually an integer value
that stores the ASCII integer value
 Char is often used as a 8 bit integer value.
 Examples:
char firstInitial = 'J'; /* stored as 74 */
char secondInitial = 'K';
Constants
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The preprocessor is a program that modifies your source file prior to
compilation.
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Common preprocessor directives are #include, which is used to include
additional code into your source file
#include <stdio.h>
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/* include standard commands*/
#define, which is used to define a constant.
#define pi 3.1415
#define id_no 12345
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Wherever the constant appears in your source file, the preprocessor
replaces it by its value. So, for instance, every "pi" in your source code
will be replace by 3.1415. The compiler will only see the value 3.1415
in your code, not "pi". Every "pi" is just replaced by its value.
Conditional Statements
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The if statement is used to conditionally execute a block of
code based on whether a test condition is true. If the condition
is true the block of code is executed, otherwise it is skipped.
int main()
{
int number = 5;
if (number == 5)
{
number = 2;
}
}
Final C comments
 C has many more syntax and command
structure which would require a lot more
training.
 One other command that might be of
interest is the ++ operator.
 In basic the command x=x+1 can be shortened
to x++. While this is confusing to most
beginners, it allows shorting of the code.
 The x++ command might even be used while
evaluating a command.
int x = 2;
if x++==2
printf(“x=/n”, int x);
Compiling the code
 In MPLAB, select the Project menu and
select the Build All command.
 The Output window will have the comments
on if the build was successful or if there are
errors.
 If there are errors, locate the error and fix.
 Be careful with where the error occurs. The
actual error can be many lines of code
before the syntax error. An example would
be a begin comment marker without an end
marker. All the code will be commented out
until the next end marker.
Loading the code into the RC
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IFI Loader is the program used to download the compiled code.
Make sure that the RC program port is plugged into a serial
com port on the computer.
Set the IFI loader to the com port plugged into.
Press the program button on the RC and then press the
download button.
The terminal window can be used in conjunction with the printf
command to display variables on the terminal window.
Remember that the printf statement will output every time the
command executes. If the printf is in the slow loop it will print
every 26.2ms or even faster in the fast loop. This may be hard
to read with the data scrolling off the screen.
The buffer is a circular buffer so it won’t fill up. The old data
won’t be there either, so you may need some type of logic to
keep the data on the screen.
Pneumatic Controls Block Diagram
Pneumatic Controls
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The air compressor is wired through a relay controlled by the
pressure switch.
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Controlling the pneumatic cylinders is then accomplished
through a single or double solenoid valve.
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When the pressure switch drops below the set switch point, the
relay is energized turning on the air compressor.
When the pressure exceeds the set switch point, the relay is deenergized turning off the air compressor.
“Single-acting” or single solenoid valve will extend the air cylinder
while the solenoid is energized. When the solenoid is deenergized, the air cylinder will close.
“Double-acting” or double solenoid valve will extend or open a air
cylinder when one of the solenoids is activated and will close when
the other solenoid is activated. After either solenoid is
deactivated, the air cylinder will remain open or closed.
These solenoid valves are controlled via a spike.
Spike Truth Table
Single Solenoid Valve (two valves wired to M+ & M-)
INPUTS
OUTPUTS
Fwd
Rev
M+
M-
Indicator
Solenoid Function
0
0
GND
GND
Orange
Off / Brake Condition (Default)
1
0
+12V
GND
Green
Solenoid1 Activates (M+)
0
1
GND
+12V
Red
Solenoid2 Activates (M-)
1
1
+12V
+12V
Off
Solenoid 1 & 2 Activates
Double Solenoid Valve (both positives wired to M+ & M- with grounds to ground block)
INPUTS
OUTPUTS
Fwd
Rev
M+
M-
Indicator
Solenoid Function
0
0
GND
GND
Orange
Off / Brake Condition (Default)
1
0
+12V
GND
Green
Solenoid Activates Direction A
0
1
GND
+12V
Red
Solenoid Activates Direction B
1
1
+12V
+12V
Off
Solenoid Activation is unknown
Summary
 There are other websites for
resources.
 The www.usfirst.org has many
presentations on the subjects
presented here.
 Hopefully this has been informative
and will help in the coming weeks.