====== Dallas 1-Wire Support ======

  * Support for Dallas 1 Wire is included on Kernel 3.14.29-29 and upwards. Make sure you are updated.
  * Will cover an example of a temperature sensor well known **DS1820** other 1 wire IC's are supported too.

<WRAP left round tip 70%>
You have to check **/etc/modprobe.d/w1_gpio.conf** file to enable the 1-wire driver.
</WRAP>
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Default GPIO for 1-Wire is **Pin #7 (GPIOX.BIT21)**

  * **Connection: With External-Supply**
{{:en:1-wire-external-power.png?750|}}

Pin 1 (Left): Ground (-)

Pin 2 (Middle): Pin #7 C2 (GPIOX.BIT21)

Pin 3 (Right): VCC (3.3V)

You also need to add a resistor from 4.7k to 10k between pin 2.

  * **Connection: Supplying the Parasite-Powered**
{{:en:1-wire-parasite-power.png?750|}}

Pin 1 (Left): Ground (-)

Pin 2 (Middle): Pin #7 C2 (GPIOX.BIT21)

Pin 3 (Right): Ground (-)

You also need to add a resistor from 4.7k to 10k between pin 2.

  * Load the required kernel modules: <code>modprobe w1-gpio && modprobe w1-therm</code>
  * Check if your sensor is working: <code>odroid@odroid64:~$ cd /sys/bus/w1/devices/
odroid@odroid64:/sys/bus/w1/devices# ls
10-000802f41d67  w1_bus_master1
odroid@odroid64:/sys/bus/w1/devices#</code>

As you can see my sensor is detected as **10-000802f38c57**, each sensor has a different id. So yours will be different.

  * Read the temperature:
<code>
odroid@odroid64:/sys/bus/w1/devices$ cd 10-000802f38c57
odroid@odroid64:/sys/bus/w1/devices/10-000802f38c57# cat w1_slave
33 00 4b 46 ff ff 03 10 30 : crc=30 YES
33 00 4b 46 ff ff 03 10 30 t=25562
odroid@odroid64:/sys/bus/w1/devices/10-000802f38c57#
</code>

Temperature is t=25562 or 25.562 degree's Celsius.


Multiple sensors can be connected on the same line as the draw below.

{{:en:untitled_sketch_bb2.png?750|}}

<code>
odroid@odroid64:/sys/bus/w1/devices# ls
10-000802f38c57  10-000802f41d67  w1_bus_master1
</code>
Two sensors in parallel.

====== Change the Default GPIO pin for 1-Wire interface ======
Ex) Default GPIO pin change to GPIOX.BIT19 \\
Please refer to below links for details related to gpio mapping in the device-tree.\\
[[https://github.com/hardkernel/linux/blob/odroidc2-3.14.y/include/dt-bindings/gpio/gxbb.h | C2 gpio mapping in the device-tree]] \\

<code>
odroid@odroid64:~$ sudo apt-get install device-tree-compiler
odroid@odroid64:~$ fdtget /media/boot/meson64_odroidc2.dtb /onewire gpios
18 113 0
odroid@odroid64:~$ fdtput /media/boot/meson64_odroidc2.dtb /onewire gpios 18 111 0
odroid@odroid64:~$ fdtget /media/boot/meson64_odroidc2.dtb /onewire gpios
18 111 0
odroid@odroid64:~$ sudo reboot
</code>
If the reboot doesn't affect the dtb update, you need a hard reset(power off/on).\\

**Use the first number in the fdtget command output when you run fdtput command. For example, 18(0x12) is the GPIO group number.**

DS1820 is connected to Pin #11

Pin 1 (Left): Ground (-)

Pin 2 (Middle): Pin #11 C2 (GPIOX.BIT19)

Pin 3 (Right): Ground (-)