title: How to use both UARTs on Raspberry Pi 3 Compute module
body: <p>I am working on a project which has a Raspberry Pi 3 Compute Module integrated into a hardware design where the PCB provides access to both Serial Ports on the compute module:</p>
  
  <ul>
  <li>One serial port with TX/RX on GPIO 14/15 (pins 51/53 of module)</li>
  <li>One serial port with CTS/RTS/TX/RX on GPIO 31/31/32/33 (pins 34/36/46/48 of the module)</li>
  </ul>
  
  <p>As far as I understand there is one full 16650 compatible UART available in the BCM2835 called the "PL011", and one mini-UART which is normally used to communicate with the internal BlueTooth chip.</p>
  
  <p>When booting Raspbian Jesse, I see the <code>/dev/ttyAMA0</code> device which seems to communicate on GPIO pins 14/15, and according to what I have read this communication runs through the PL011 full UART chip. I have tried to create a <code>/boot/config.txt</code> file which has the following device tree overlays:</p>
  
  <pre><code>dtoverlay=uart1,txd1_pin=32,rxd1_pin=33
  enable_uart=1
  </code></pre>
  
  <p>This does not seem to provide me with a <code>/dev/ttyAMA1</code> device. This seems consistent with the description in the <code>/boot/overlays/README</code> file which states:</p>
  
  <pre><code>Name: Uart1
  Info: Enable uart1 in place of uart0
  </code></pre>
  
  <p>I did find a limited driver for the mini-UART which is fixed at 115200 baud, which seems like a driver to use the mini-UART instead of the full UART.</p>
  
  <p>What I'd like to do is: without redesigning the hardware, configure the "PL011" full UART to use the CTS/RTS/TX/RX port, <em>and</em> the mini-UART to use the TX/RX port, so that I can use <em>both</em> serial ports in my application.</p>