Heres the slightly modified master reader sketch from the wire libray examples, the slave ping code i got off the net, i'll try and find the original , which has inches to seconds conversion and is fully commented and may has an author. The ultrasonic sensor is from radio shack; 3 pin (plugs into breadboard). the master sketch delay probably has to be adjusted down to get more pings. Also if you're using processing to read serial you can multiply by n the final result of the ping calculation - return (microseconds / 29 / 2)*n;
if you need to scale it and dont know how in processing. the slave code is above(posted by nick), heres the master incase you were wondering.
Thanks again to Nick
Wire Master Reader
// by Nicholas Zambetti <http://www.zambetti.com>
// Demonstrates use of the Wire library
// Reads data from an I2C/TWI slave device
// Refer to the "Wire Slave Sender" example for use with this
// Created 29 March 2006
// This example code is in the public domain.
#include <Wire.h>
void setup()
{
Wire.begin(); // join i2c bus (address optional for master)
Serial.begin(9600); // start serial for output
}
void loop()
{
Wire.requestFrom(2, 1); // request 1 bytes from slave device #2
while(Wire.available()) // slave may send less than requested
{
char c = Wire.read(); // receive a byte as character
Serial.print(c,DEC);
Serial.print("\t"); // I tab the data so i can copy and import
//to labview and see it on strip chart, wavegraph etc
}
delay(500);
}