SRF02.cpp

00001 
00002 
00003 /*Library for SRF02 ultrasonic range finder*/
00004 #include "SRF02.h"
00005 
00006 
00007 
00008 SRF02::SRF02(PinName sda, PinName scl, int addr) : m_i2c(sda, scl), m_addr(addr){
00009     //no initialisation code required here
00010     }
00011     
00012 SRF02::~SRF02(){
00013 
00014 }
00015 
00016 float SRF02::measurecm() {
00017    float result = dosonar(0x51);
00018    return result;
00019 }
00020 
00021 float SRF02::measureus() {
00022    float result = dosonar(0x52);
00023    return result;
00024 }
00025 
00026 float SRF02::measurein() {
00027    float result = dosonar(0x50);
00028    return result;
00029 }
00030 
00031 
00032 float SRF02::dosonar(char rangetype){
00033     //local variables
00034     const char m_addr = 0xE0;  //srf02 default slave address
00035     char commandsequence[2];
00036     
00037     // Get range data from SRF02 in cm
00038         // Send Tx burst command over I2C bus
00039         commandsequence[0] = 0x00;               // Command register
00040         commandsequence[1] = rangetype;          // Ranging results type
00041         m_i2c.write(m_addr, commandsequence, 2); // Request ranging from sensor
00042         wait(0.07);  // Average wait time for sonar pulse and processing
00043         // Read back range over I2C bus
00044         commandsequence[0] = 0x02;                   // 
00045         m_i2c.write(m_addr, commandsequence, 1, 1);  // 
00046         m_i2c.read(m_addr, commandsequence, 2);             // Read two-byte echo result
00047         //combine upper and lower bytes in to a single value
00048         float range = ((commandsequence[0] << 8) + commandsequence[1]);
00049         return range;
00050 
00051 }
00052