Revision 2:cb489f486ece, committed 2016-06-22

Comitter:

eencae

Date:

Wed Jun 22 15:49:12 2016 +0000

Parent:

1:8e6587d88773

Commit message:

Added method to change the address of the sensor on the bus. Address is specified using the constructor method.

Changed in this revision

diff -r 8e6587d88773 -r cb489f486ece SRF02.cpp
--- a/SRF02.cpp	Sun Mar 08 14:21:40 2015 +0000
+++ b/SRF02.cpp	Wed Jun 22 15:49:12 2016 +0000
@@ -7,12 +7,15 @@
 #include "mbed.h"
 #include "SRF02.h"
 
-SRF02::SRF02(PinName sdaPin, PinName sclPin)
+SRF02::SRF02(PinName sdaPin, PinName sclPin, char addr)
 {
     i2c = new I2C(sdaPin,sclPin); // create new I2C instance and initialise
     i2c->frequency(400000);       // I2C Fast Mode - 400kHz
     leds = new BusOut(LED4,LED3,LED2,LED1);
 
+    w_addr_ = addr; // set write address of sensor
+    r_addr_ = w_addr_ + 1;  // read address has the lowest bit set (i.e. + 1)
+
 }
 
 int SRF02::getDistanceCm()
@@ -22,7 +25,7 @@
     // need to send CM command to command register
     data[0] = CMD_REG;
     data[1] = CM_CMD;
-    int ack = i2c->write(SRF02_W_ADD,data,2);  
+    int ack = i2c->write(w_addr_,data,2);  
     if (ack)
         error();  // if we don't receive acknowledgement, flash error message
         
@@ -31,12 +34,12 @@
     
     // we can now read the result - tell the sensor we want the high byte
     char reg = RANGE_H_REG;   
-    ack = i2c->write(SRF02_W_ADD,&reg,1);  
+    ack = i2c->write(w_addr_,&reg,1);  
     if (ack)
         error();  // if we don't receive acknowledgement, flash error message
     
     // if we read two bytes, the register is automatically incremented (H and L)
-    ack = i2c->read(SRF02_R_ADD,data,2); 
+    ack = i2c->read(r_addr_,data,2); 
     if (ack)
         error();  // if we don't receive acknowledgement, flash error message
 
@@ -44,6 +47,47 @@
     return (data[0] << 8) | data[1];
 }
 
+void SRF02::changeAddress(char addr) {
+    
+    char data[2];
+    
+    // sequence to change I2C (https://www.robot-electronics.co.uk/htm/srf02techI2C.htm)
+    // need to write this sequence to the command register, followed by the new address
+    
+    data[0] = CMD_REG;
+    data[1] = 0xA0;  // 1st byte in sequence
+    int ack = i2c->write(w_addr_,data,2);  
+    if (ack)
+        error();  // if we don't receive acknowledgement, flash error message
+        
+    wait_ms(50);  // small delay in between 
+    
+    data[0] = CMD_REG;
+    data[1] = 0xAA;   // 2nd byte in sequence
+    ack = i2c->write(w_addr_,data,2);  
+    if (ack)
+        error();  // if we don't receive acknowledgement, flash error message
+        
+    wait_ms(50); // small delay in between 
+    
+    data[0] = CMD_REG;
+    data[1] = 0xA5;  // 3rd byte in sequence
+    ack = i2c->write(w_addr_,data,2);  
+    if (ack)
+        error();  // if we don't receive acknowledgement, flash error message
+        
+    wait_ms(50);  // small delay in between 
+    
+    data[0] = CMD_REG;  
+    data[1] = addr;  // new address
+    ack = i2c->write(w_addr_,data,2);  
+    if (ack)
+        error();  // if we don't receive acknowledgement, flash error message
+    
+    wait_ms(50);
+    
+}
+
 void SRF02::error()
 {
     while(1) {

diff -r 8e6587d88773 -r cb489f486ece SRF02.h
--- a/SRF02.h	Sun Mar 08 14:21:40 2015 +0000
+++ b/SRF02.h	Wed Jun 22 15:49:12 2016 +0000
@@ -8,10 +8,6 @@
 #ifndef SRF02_H
 #define SRF02_H
 
-// addresses
-#define SRF02_R_ADD    0xE1
-#define SRF02_W_ADD    0xE0
-
 // registers
 #define CMD_REG         0x00
 #define RANGE_H_REG     0x02
@@ -28,16 +24,18 @@
 @brief Library for interfacing with SRF02 Ultrasonic Sensor in I2C
 @see http://www.robot-electronics.co.uk/htm/srf02tech.htm
 
-@brief Revision 1.0
+@brief Revision 1.1
 
 @author Craig A. Evans
-@date   March 2014
+@date   June 2016
  *
  * Example:
  * @code
 
  #include "mbed.h"
  #include "SRF02.h"
+ 
+ SRF02 sensor(p28,p27,0xE0);  // SDA, SCL, address
 
  int main() {
 
@@ -62,15 +60,22 @@
     *
     * @param sdaPin - mbed SDA pin 
     * @param sclPin - mbed SCL pin
+    * @param addr - write address of the SRF02 sensor 
     * 
     */
-    SRF02(PinName sdaPin, PinName sclPin);
+    SRF02(PinName sdaPin, PinName sclPin, char addr);
     /** Read distance in centimetres
     *
     * @returns distance in centimetres (int)
     * 
     */
     int getDistanceCm();
+    /** Change I2C address of SRF02  sensor
+    *
+    * @param address - @see https://www.robot-electronics.co.uk/htm/srf02techI2C.htm for valid addresses
+    *
+    */
+    void changeAddress(char addr);
 
 private:
     /** Hangs in infinite loop flashing 'blue lights of death'
@@ -82,6 +87,9 @@
 private:  // private variables
     I2C* i2c;
     BusOut* leds;
+    
+    char w_addr_; // write address of sensor
+    char r_addr_; // read address (= write address + 1)
 };
 
 #endif
\ No newline at end of file