abstandsmesser.cpp

00001 /***************************************************************************************/
00002 /*****************        Facharbeit Jannick Pötzel 23.12.2011    **********************/
00003 /*****************         SRF08 Ultrasonic Range Finder          **********************/
00004 /***************************************************************************************/
00005 
00006 #include "mbed.h"
00007 #include "TextLCD.h"
00008 
00009 
00010 // allocation of variables
00011 TextLCD lcd(p24, p25, p26, p27, p28, p29, p30);
00012 
00013 DigitalOut mled0(LED1);
00014 DigitalOut mled1(LED2);
00015 DigitalOut mled2(LED3);
00016 DigitalOut mled3(LED4);
00017 
00018 I2C sonar(p9, p10);                         // Define SDA, SCL pins
00019 Serial pc(USBTX, USBRX);                    // Define Tx, Rx for PC
00020 const int addr = 0xE0;                      // I2C device address for SRF08
00021 char cmd[2];
00022 char echo[2];
00023 
00024 // start amin programm
00025 int main() {
00026 
00027 // Set up SRF08 max range and receiver sensitivity over I2C bus
00028     cmd[0] = 0x02;                          // Range register
00029     cmd[1] = 0x1C;                          // Set max range about 100cm
00030     sonar.write(addr, cmd, 2);
00031     cmd[0] = 0x01;                          // Receiver gain register
00032     cmd[1] = 0x1B;                          // Set receiver gain
00033     sonar.write(addr, cmd, 2);
00034 
00035 while(1)
00036 {
00037 
00038 // Get range data from SRF08
00039 // Send Tx burst command over I2C bus
00040         cmd[0] = 0x00;                      // Command register
00041         cmd[1] = 0x51;                      // Ranging results in cm
00042         sonar.write(addr, cmd, 2);          // Send ranging burst
00043 
00044         wait(0.07);                         // Wait for return echo
00045 
00046 // Read back range over I2C bus
00047         cmd[0] = 0x02;                      // Address of first echo
00048         sonar.write(addr, cmd, 1, 1);       // Send address of first echo       
00049         sonar.read(addr, echo, 2);          // read two-byte echo result
00050        
00051 // calculate distance            
00052       int x = (echo[0]<<8)+echo[1];
00053 
00054 // clear LCD       
00055       lcd.cls();
00056 // if distance bigger than 99 cm write out of R to LCD
00057       if (x > 99)
00058       {
00059       lcd.writeData(' ');
00060       lcd.writeData('o');
00061       lcd.writeData('u');
00062       lcd.writeData('t');
00063       lcd.writeData(' ');
00064       lcd.writeData('o');
00065       lcd.writeData('f');
00066       lcd.writeData(' ');
00067       lcd.writeData('R');
00068       }
00069 // write distance to LCD
00070       else
00071       {
00072       int x1=0x30+x%10;
00073       int x2=x/10;
00074       x2=0x30+x2%10;
00075       lcd.writeData(' ');
00076       lcd.writeData(x2);
00077       lcd.writeData(x1);
00078       lcd.writeData(' ');
00079       lcd.writeData('c');
00080       lcd.writeData('m');
00081       }
00082 
00083 // Power in LEDs in dependence of measured distance
00084       
00085         if (x <= 40)
00086         {
00087             mled0 = 1;
00088             mled1 = 0;
00089             mled2 = 0;
00090             mled3 = 0; 
00091         }
00092        if (x <= 30)
00093         {
00094            mled0 = 1;
00095            mled1 = 1;
00096            mled2 = 0;
00097            mled3 = 0;
00098         }
00099        if (x <= 20)
00100         {
00101           mled0 = 1;
00102           mled1 = 1;
00103           mled2 = 1;
00104           mled3 = 0;
00105         }
00106        if (x <= 10)
00107         {
00108           mled0 = 1;
00109           mled1 = 1;
00110           mled2 = 1;
00111           mled3 = 1;
00112         }
00113        else if (x > 40)
00114         {
00115           mled0 = 0;
00116           mled1 = 0;
00117           mled2 = 0;
00118           mled3 = 0;
00119         }
00120   }       
00121 }