Multiple I2C Devices connected parallel I have two Lidar Lites, connected to one APM. I have no issue with getting data from one of them, i use the code below 

#include &lt;I2C.h&gt;
#define    LIDARLite_ADDRESS   0x62          // Default I2C Address of LIDAR-Lite.
#define    RegisterMeasure     0x00          // Register to write to initiate ranging.
#define    MeasureValue        0x04          // Value to initiate ranging.
#define    RegisterHighLowB    0x8f          // Register to get both High and Low bytes in 1 call.


void setup(){
  Serial.begin(9600); //Opens serial connection at 9600bps.     
  I2c.begin(); // Opens &amp; joins the irc bus as master
  delay(100); // Waits to make sure everything is powered up before    sending or receiving data  
  I2c.timeOut(50); // Sets a timeout to ensure no locking up of sketch if I2C communication fails
}

void loop(){
 // Write 0x04 to register 0x00
  uint8_t nackack = 100; // Setup variable to hold ACK/NACK resopnses     
  while (nackack != 0){ // While NACK keep going (i.e. continue     polling until sucess message (ACK) is received )
    nackack = I2c.write(LIDARLite_ADDRESS,RegisterMeasure, MeasureValue); // Write 0x04 to 0x00
    delay(1); // Wait 1 ms to prevent overpolling
  }

  byte distanceArray[2]; // array to store distance bytes from read function

  // Read 2byte distance from register 0x8f
  nackack = 100; // Setup variable to hold ACK/NACK resopnses     
  while (nackack != 0){ // While NACK keep going (i.e. continue polling until sucess message (ACK) is received )
    nackack = I2c.read(LIDARLite_ADDRESS,RegisterHighLowB, 2, distanceArray); // Read 2 Bytes from LIDAR-Lite Address and store in    array
   delay(1); // Wait 1 ms to prevent overpolling
  }
  int distance = (distanceArray[0] &lt;&lt; 8) + distanceArray[1];  // Shift high byte [0] 8 to the left and add low byte [1] to create 16-bit int

  // Print Distance
  Serial.println(distance);
}


i can get the distance fine, now have two connected, as follows



So my noob question is how to i get data from the 2, my guess is the wiring is ok.

I am using the code from https://github.com/PulsedLight3D/LIDARLite_v2_Arduino_Library

any help would be appreciated. thanks.
Connect one at a time and run the change address sketch mentioned by Yeti.

Naturally change each one (one at a time) to different addresses (ex. 0x62, 0x64, 0x66).


  i still don't know whats the address of the 2nd one 


The address is what you change it to.

Then connect them all back up again and run the I2C scanner. You should see all 3 addresses.




  documents state that address changes will be gone when i power it off


If that is true, save the address for each module in EEPROM. Then use that code to change the module address in setup.



See the address in the code you posted?

#define    LIDARLite_ADDRESS   0x62          // Default I2C Address of LIDAR-Lite.


If you don't want to save the address in EEPROM just upload three versions of the sketch with a different address in each one. Note that the address must be even (eg. 0x62, 0x64, 0x66).

But it would be very simple just to read from EEPROM in setup and keep the address in a variable rather than a #define.