user34829: I am trying to use four of the same accelerometer on the same bus and acquire data from each of them using an SD card. Because I am using four of the same accelerometer I need to be able to differentiate between them and I dont know how to find their specific address. I need the specific address so I can tell my arduino which accelerometer to pull data from. essentially it would pull data from 1 then 2 then 3 then 4 and loop back to 1.

user4143: You can't have 4 of those on one bus. The maximum is 2.
The pin SA0 defines the least significant bit of the I2C address. From the datasheet:

7 | SA0 | I2C least significant bit of the device I2C address, I2C 7-bit address = 0x1C (SA0 = 0), 0x1D (SA0 = 1). 

In fact, as it states on the Adafruit website (if you'd care to read it sometime):

A is the I2C Address select pin. By default this is pulled down to ground with a 10K resistor, for an I2C address of 0x1C. You can also connect it to the 3Vo pin for an address of 0x1D

If you want more than 2 you will either have to have multiple I2C busses or use an I2C multiplexer (such as this one) to select different branches on the same bus.

34829: <p>I am trying to use four of the same accelerometer on the same bus and acquire data from each of them using an SD card. Because I am using four of the same accelerometer I need to be able to differentiate between them and I dont know how to find their specific address. I need the specific address so I can tell my arduino which accelerometer to pull data from. essentially it would pull data from 1 then 2 then 3 then 4 and loop back to 1.</p>
 4143: <p>You can't have 4 of those on one bus. The maximum is 2.</p>

<p>The pin <code>SA0</code> defines the least significant bit of the I2C address. From <a href="http://www.nxp.com/assets/documents/data/en/data-sheets/MMA8451Q.pdf" rel="nofollow noreferrer">the datasheet</a>:</p>

<blockquote>
  <p>7 | SA0 | I2C least significant bit of the device I2C address, I2C 7-bit address = 0x1C (SA0 = 0), 0x1D (SA0 = 1). </p>
</blockquote>

<p>In fact, as it states on the <a href="https://learn.adafruit.com/adafruit-mma8451-accelerometer-breakout/pinouts" rel="nofollow noreferrer">Adafruit website</a> (if you'd care to read it sometime):</p>

<blockquote>
  <p>A is the I2C Address select pin. By default this is pulled down to ground with a 10K resistor, for an I2C address of 0x1C. You can also connect it to the 3Vo pin for an address of 0x1D</p>
</blockquote>

<p>If you want more than 2 you will either have to have multiple I2C busses or use an I2C multiplexer (such as <a href="https://learn.adafruit.com/adafruit-tca9548a-1-to-8-i2c-multiplexer-breakout/overview" rel="nofollow noreferrer">this one</a>) to select different branches on the same bus.</p>
