Diff: main.cpp

Revision:

0:f154cd1e30ff

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Thu Dec 16 10:52:45 2010 +0000
@@ -0,0 +1,106 @@
+// EDP & mbed demonstration program using I2C and PWM: W.G.Marshall 2010
+// Requires EDP-AM-MC1 DC motor module
+// Uses SRF08 Ultrasonic Range Finder on I2C address 0xE0
+// Option link J217 on EDP mbed carrier changed from 1-2 to 2-3
+// Jumpers on EDP MC1 module will require setting to suit GPIO signals
+
+#include "mbed.h"
+
+I2C sonar(p9, p10);                         // Define SDA, SCL pins
+Serial pc(USBTX, USBRX);                    // Define Tx, Rx pins
+PwmOut motor(p23);                          // Define PWM output (EDP: EVG0_GPIO40)
+DigitalOut Brake(p19);                      // Define brake      (EDP: GPIO0)
+DigitalOut Direction(p24);                  // Define direction  (EDP: EVG1_GPIO42)
+DigitalOut L1(LED1);                        // User LEDs form bargraph
+DigitalOut L2(LED2);
+DigitalOut L3(LED3);
+DigitalOut L4(LED4);
+
+const int addr = 0xE0;                      // I2C device address for SRF08
+char cmd[2];
+char echo[3];
+// echo[0] = light level
+// echo[1] = MSB echo
+// echo[2] = LSB echo
+float temp8;
+float range;   
+float MotorPWM;
+
+int main() {
+
+// Set up SRF08 max range and receiver sensitivity
+    cmd[0] = 0x02;                          // Range register
+    cmd[1] = 0x1C;                          // Set max range about 100cm
+    sonar.write(addr, cmd, 2);
+    cmd[0] = 0x01;                          // Receiver gain register
+    cmd[1] = 0x1B;                          // Set max receiver gain
+    sonar.write(addr, cmd, 2);
+
+// Set up PWM and motor control
+    motor.period(0.00005);                  // Set PWM frequency = 20kHz
+    motor.write(1);                         // Motor speed = 0
+    Brake = 0;                              // Brake on = 1, Brake off = 0
+    Direction = 0;
+   
+    printf("\n\n\rCollision Avoidance Program Vsn 1.2\n\r");
+    printf("\n\r Range   Light\n\r");
+    
+    while (1) {
+    
+// Get range data and light level from SRF08
+// Send Tx burst command over I2C bus
+        cmd[0] = 0x00;                      // Command register
+        cmd[1] = 0x51;                      // Ranging results in cm
+        sonar.write(addr, cmd, 2);          // Send ranging burst
+
+        wait(0.07);
+
+// Read back light level and range over I2C bus
+        cmd[0] = 0x01;                      // Address of light level
+        sonar.write(addr, cmd, 1, 1);       // Send address of light level       
+        sonar.read(addr, echo, 3);          // read light and echo result
+        
+// Generate PWM mark/space ratio from range data
+        range = (echo[1]<<8)+echo[2];
+        MotorPWM = range/100;               // Turn range into PWM ratio
+        if (temp8 != 0) {
+           motor.write(1-MotorPWM);         // Update PWM ratio (0 -> 1.0)
+        }
+        else {
+           motor.write(1);                  // PWM ratio = 0
+        }
+        pc.printf("  %3.0f", range);
+        pc.printf("     %3d\r", echo[0]);
+        
+// Keyboard input to toggle start/stop motor
+        if (pc.readable()) {                // Check for keyboard input
+           pc.getc();                       // Key pressed, clear buffer 
+           if (temp8 == 0) {                // Motor already stopped?
+              Brake = 0;                    // Brake off, start motor
+              temp8 = range;
+           }
+           else {                           // Motor running
+              Brake = 1;                    // Brake on, stop motor
+              temp8 = 0;
+           }
+        }
+        wait(0.1);                          // Wait for 100ms
+
+// Bargraph with mbed user LEDs
+        if (range > 70) {
+           L1 = 1, L2 = 1, L3 = 1, L4 = 1;
+        }
+        else if (range > 40) {
+           L1 = 1, L2 = 1, L3 = 1, L4 = 0;
+        }
+        else if (range > 25) {
+           L1 = 1, L2 = 1, L3 = 0, L4 = 0;
+        }
+        else if (range > 7) {
+           L1 = 1, L2 = 0, L3 = 0, L4 = 0;
+        }
+        else {
+           L1 = 0, L2 = 0, L3 = 0, L4 = 0;
+        }
+    }
+}