user54819: According to the Arduino pin Mapping
20  PB12    SDA 3   6
21  PB13    SCL 3   6
70  PA17    SDA1    3   6
71  PA18    SCL2    15  9

The first one seems pretty obvious, the second one though is confusing. They have different labels. I also do not see other SDA or SCL in the table. So is this a typo?

user31105: According to the Wire library documentation https://forum.arduino.cc/index.php?topic=132130.0:

The Arduino Due has two I2C / TWI interfaces SDA1 and SCL1 are near to
  the AREF pin and the additional one is on pins 20 and 21.

And the table:
Arduino Due: 20 (SDA), 21 (SCL), SDA1, SCL1
So it seems in your table SCL2 should be SCL1.

54819: <p>According to the <a href="https://www.arduino.cc/en/Hacking/PinMappingSAM3X" rel="nofollow noreferrer">Arduino pin Mapping</a></p>

<pre><code>20  PB12    SDA 3   6
21  PB13    SCL 3   6
70  PA17    SDA1    3   6
71  PA18    SCL2    15  9
</code></pre>

<p>The first one seems pretty obvious, the second one though is confusing. They have different labels. I also do not see other SDA or SCL in the table. So is this a typo?</p>
 31105: <p>According to the Wire library documentation <a href="https://forum.arduino.cc/index.php?topic=132130.0" rel="nofollow noreferrer">https://forum.arduino.cc/index.php?topic=132130.0</a>:</p>

<blockquote>
  <p>The Arduino Due has two I2C / TWI interfaces SDA1 and SCL1 are near to
  the AREF pin and the additional one is on pins 20 and 21.</p>
</blockquote>

<p>And the table:</p>

<p>Arduino Due: 20 (SDA), 21 (SCL), SDA1, SCL1</p>

<p>So it seems in your table SCL2 should be SCL1.</p>
