ARM Summer Students 2013 Workshop

Table of Contents

  1. Welcome to the ARM Summer Workshop!
  2. Documents
  3. Useful numbers
  4. Library
  5. Hello World
  6. Example

Welcome to the ARM Summer Workshop!

/media/uploads/CBindahouse/_scaled_pololu_m3pi.jpg

Documents

Useful numbers

  • Speed of rotation: 720 degrees per second at half speed
  • Forward/Backward: 470mm per second at half speed

Library

Import library
m3pi - m3pi Class Reference

Public Member Functions

m3pi ()
Create the m3pi object connected to the default pins.
m3pi (PinName nrst, PinName tx, PinName rx)
Create the m3pi object connected to specific pins.
void reset (void)
Force a hardware reset of the 3pi.
void left_motor (float speed)
Directly control the speed and direction of the left motor.
void right_motor (float speed)
Directly control the speed and direction of the right motor.
void forward (float speed)
Drive both motors forward as the same speed.
void backward (float speed)
Drive both motors backward as the same speed.
void left (float speed)
Drive left motor backwards and right motor forwards at the same speed to turn on the spot.
void right (float speed)
Drive left motor forward and right motor backwards at the same speed to turn on the spot.
void stop (void)
Stop both motors.
float pot_voltage (void)
Read the voltage of the potentiometer on the 3pi.
float battery (void)
Read the battery voltage on the 3pi.
float line_position (void)
Read the position of the detected line.
char sensor_auto_calibrate (void)
Calibrate the sensors.
void calibrate (void)
Set calibration manually to the current settings.
void reset_calibration (void)
Clear the current calibration settings.
void leds (int val)
Write to the 8 LEDs.
void locate (int x, int y)
Locate the cursor on the 8x2 LCD.
void cls (void)
Clear the LCD.
int putc (int c)
Send a character directly to the 3pi serial interface.
int getc ()
Receive a character directly to the 3pi serial interface.
int print (char *text, int length)
Send a string buffer to the 3pi serial interface.

Hello World

Repository: m3pi_HelloWorld

Example

Import program
m3pi_LineFollower - main.cpp

00001 #include "mbed.h"
00002 #include "m3pi.h"
00003 
00004 m3pi m3pi;
00005 
00006 int main() {
00007 
00008     // Parameters that affect the performance
00009     float speed = 0.2;
00010     float correction = 0.1;   
00011     float threshold = 0.5;
00012 
00013     m3pi.locate(0,1);
00014     m3pi.printf("Line Flw");
00015 
00016     wait(2.0);
00017     
00018     m3pi.sensor_auto_calibrate();
00019     
00020     while (1) {
00021 
00022         // -1.0 is far left, 1.0 is far right, 0.0 in the middle
00023         float position_of_line = m3pi.line_position();
00024 
00025         // Line is more than the threshold to the right, slow the left motor
00026         if (position_of_line > threshold) {
00027             m3pi.right_motor(speed);
00028             m3pi.left_motor(speed-correction);
00029         }
00030 
00031         // Line is more than 50% to the left, slow the right motor
00032         else if (position_of_line < -threshold) {
00033             m3pi.left_motor(speed);
00034             m3pi.right_motor(speed-correction);
00035         }
00036 
00037         // Line is in the middle
00038         else {
00039             m3pi.forward(speed);
00040         }
00041     }
00042 }
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