====== UART interface using the Tinkering Kit ======
There are two UART ports on the C2. \\
They are 3.3Volt (LVTTL) interface and there is no 5Volt tolerance.

The first one is mapped to /dev/ttyS1 which is connected to 40-pin header Pin #8 & #10 & ground pin.\\

The second one is mapped to /dev/ttyS0 which is connected to Serial Console Port CON5.

==== How to test external UART pin on the 40-pin header ====

You need to prepare below items.
  * **ODROID-C2**
  * USB-UART Module Kit
  * jumper wire x4
  * serial comunication utility on your Host PC

You will connect jumper wire as below picture.\\
Connect the USB-PORT of USB-UART Module to your HOST PC\\
**The RXD and TXD must be twisted each other.**\\

{{:en:c1:odroidc1_uart.jpg?300|}}

1. HOST PC setup.\\
You will open USB Module Device on your HOST PC.\\
**Ubuntu**\\
Install serial comunication utility.
  sudo apt-get install minicom
After check your usb serial node, Open serial port.
  ls /dev/ttyUSB*
  sudo minicom -b 115200 -D /dev/ttyUSB0
  
2. Target board(**ODROID-C2**) setup.\\
Set a serial node on your **ODROID-C2**
  stty -F /dev/ttyS1 115200

3. **ODROID-C2** -> HOST PC test.\\
**ODROID-C2**
  echo 1 > /dev/ttyS1
  
4. HOST PC -> **ODROID-C2** test.\\
**ODROID-C2**
  cat /dev/ttyS1
HOST PC\\
Send characters via minicom.

==== Pin Map : UART pin on the 4-pin CON5 connector ====
<code>
_____UART____
|           |
|Pin 4 - GND|
|Pin 3 - RXD|
|Pin 2 - TXD|
|Pin 1 - VCC|
|_          |
  |_________|
</code>
3.3V LVTTL


==== Another UART port on 40pin header ====
If you don't use an I2C interface(i2c-1) on pin#3 & pin#5, you can use them to activate the UART2.\\
Just follow **campbell**'s development note to have a new UART2 port via /dev/ttyS2.\\
Note that Pin#3(SDA1) is mapped to Tx and Pin#5(SCL1) is Rx.\\
[[http://forum.odroid.com/viewtopic.php?f=139&t=25371|How to enable a third UART ttyS2 by "campbell"]]


==== Automatically configure the UART settings. ====
This is an example of default setting for a GPS module which has a 9600bpsN81 UART interface.\\
Add the following to the end of /etc/rc.local (before the exit 0)\\
<code>/bin/stty -F /dev/ttyS2 raw 9600 cs8 clocal -cstopb > /dev/null 2>&1</code>
This way the tty port is setup for use with the gps on system boot, without user interaction.\\


=== Tips for UART port ===
[[http://forum.odroid.com/viewtopic.php?f=115&t=17279|How to enable the RTS/CTS]]

==== How to enable UART_B and UART_C ports ====
Up to 4 ports can be used for UART in ODROID-C2---UART_A0(Serial console), UART_A, UART_B and UART_C.\\
There are UART_A, UART_B and UART_C in [[http://odroid.com/dokuwiki/doku.php?id=en:c2_hardware#expansion_connectors|expansion connectors of ODROID-C2]].

  * //<UART pin>// | //<Pin number>// 
  * UART_A TX | 8
  * UART_A RX | 10
  * UART_B TX | 3
  * UART_B RX | 5
  * UART_C TX | 32
  * UART_C RX | 26

In order to enable UART_B and UART_C ports, it is necessary to modify the //meson64_odroidc2.dts// file.

1. Kernel source download

<code>
sudo apt-get update
sudo apt-get install git
git clone --depth 1 https://github.com/hardkernel/linux.git -b odroidc2-3.14.y
</code>

2. Delete I2C_A definition

I2C_A uses same pins as UART_B by pinmux. So, i2c_a definition needs to be removed.

  * //($LINUX)/arch/arm64/boot/dts/meson64_odroidc2.dts//
<code>
iff --git a/arch/arm64/boot/dts/meson64_odroidc2.dts b/arch/arm64/boot/dts/meson64_odroidc2.dts
index e6a25b0..db09b04 100755
--- a/arch/arm64/boot/dts/meson64_odroidc2.dts
+++ b/arch/arm64/boot/dts/meson64_odroidc2.dts
@@ -813,18 +813,6 @@
 
 };
 
-&i2c_a {
-       status = "okay";
-
-       /* Hardkernel I2C RTC */
-       pcf8563: pcf8563@51     {
-               status = "disabled";
-               compatible = "nxp,pcf8563";
-               reg = <0x51>;
-               #clock-cells = <0>;
-       };
-};
-
 &i2c_b {
        status = "okay";

</code>

3. Add UART_B and UART_C definitions
  * //($LINUX)/arch/arm64/boot/dts/meson64_odroidc2.dts//
<code>
diff --git a/arch/arm64/boot/dts/meson64_odroidc2.dts b/arch/arm64/boot/dts/meson64_odroidc2.dts
index e6a25b0..fd41552 100755
--- a/arch/arm64/boot/dts/meson64_odroidc2.dts
+++ b/arch/arm64/boot/dts/meson64_odroidc2.dts
@@ -31,6 +31,8 @@
        aliases {
                serial0 = &uart_AO;
                serial1 = &uart_A;
+               serial2 = &uart_B;
+               serial3 = &uart_C;
        };
 
        gpu_dvfs_tbl: gpu_dvfs_tbl {
@@ -459,6 +461,32 @@
                pinctrl-0 = <&a_uart_pins>;
        };
 
+       uart_B: serial@c11084dc {
+               compatible = "amlogic, meson-uart";
+               reg = <0x0 0xc11084dc 0x0 0x18>;
+               interrupts = <0 75 1>;
+               status = "okay";
+               clocks = <&clock CLK_XTAL>;
+               clock-names = "clk_uart";
+               fifosize = < 64 >;
+               pinctrl-names = "default";
+               pinctrl-0 = <&b_uart_pins>;
+               resets = <&clock GCLK_IDX_UART1>;
+       };
+
+       uart_C: serial@c1108700 {
+               compatible = "amlogic, meson-uart";
+               reg = <0x0 0xc1108700 0x0 0x14>;
+               interrupts = <0 93 1>;
+               status = "okay";
+               clocks = <&clock CLK_XTAL>;
+               clock-names = "clk_uart";
+               fifosize = < 64 >;
+               pinctrl-names = "default";
+               pinctrl-0 = <&c_uart_pins>;
+               resets = <&clock GCLK_IDX_UART2>;
+       };
+
        canvas {
                compatible = "amlogic, meson, canvas";
                dev_name = "amlogic-canvas";
</code>

  * [[https://gist.githubusercontent.com/bkrepo/ae548109e3f94fd41fed2defa270057b/raw/b50265071e0c4bfe22fcc418aba938bf843bfa8a/meson64_odroidc2.dts|meson64_odroidc2.dts]]

4. Install modified dtb file
<code>
make odroidc2_defconfig
make dtbs
sudo cp -f arch/arm64/boot/dts/meson64_odroidc2.dtb /media/boot/
sudo reboot
</code>
5. Done