title: A20 OLinuXino-Micro 4GB from Olimex - understanding GPIOs
body: <p>i am using a A20 OLinuXino Micro 4GB from Olimex with Debian on SD Card.</p>
  
  <p>I want to use the GPIOs and have some short question about the configuration of the GPIOs. The GPIO-1 connector on the board has pins numbered from 1 to 39. In the manual I have entries like that:</p>
  
  <p>Pin # | Signal name  | Processor pin</p>
  
  <p>23 | PG9 | C19</p>
  
  <p>...</p>
  
  <p>39 | LRADC1 | AB22</p>
  
  <p>In the fex file, I find this:</p>
  
  <pre><code>[gpio_para]
  gpio_used = 1
  gpio_num = 64
  ...
  gpio_pin_10 = port:PG09&lt;0&gt;&lt;default&gt;&lt;default&gt;&lt;default&gt;
  </code></pre>
  
  <p>How is defined that the processor pin C19 is routed to port PG9? 
  And port means exactly what?</p>
  
  <p>How is defined that the port PG9 is routed to pin23 of the connector?</p>
  
  <p>Can the gpio_pin_10 designation be chosen arbitrarily?</p>
  
  <p>At the end I would like to use the LRADC1, to sample a signal, but the fex file doesn't have any LRADC1 entry. Why is that?</p>
  
  <p>Maybe somebody could answer may questions in 2 or 3 sentences so it makes sense to the rest of what I read. Thanks!</p>