====== 1-Wire ======

===== Introduction =====

This page introduces the usage of 1-Wire bus on [[products:sbc:common:applications:gpio:40pin-header|40-Pin Header]].

===== 1-Wire Information =====

You can find the default PIN used for ''1-Wire'' bus from the table below.

|           ^  PIN  ^  GPIO Name  ^  DT Overlays Node  ^  Device Node          ^
^  VIM1/2   |  37   |  GPIOH_5    |  onewire           |  /sys/bus/w1/devices  |
^  VIM3/3L  |  15   |  GPIOH_6    | :::                | :::                   |
^  VIM4     |  37   |  GPIOT_19   | :::                | :::                   |
^  VIM1S    |  36   |  GPIOZ_8    | :::                | :::                   |
^  Edge1    |  30   |  GPIO4_A0   | :::                | :::                   |
|           |       |             | :::                | :::                   |

===== Enable 1-Wire Bus =====

In order to use the 1-Wire, you need to enable the ''1-Wire'' function via [[products:sbc:common:configurations:device-tree-overlay|Device Tree Overlay]].

<tabbox VIM1/2/3/3L/Edge1>

Edit ''/boot/env.txt'' to add the onewire node to ''overlays'' node if it doesn't exist.

Take VIM3 as an example to enable ''1-Wire'', you need to add ''onewire'' node to ''overlays'' node if it doesn't exist.

```shell
overlays=onewire
```
<tabbox VIM3 with 5.15 kernel>

Edit ''/boot/dtb/amlogic/kvim3.dtb.overlay.env'' to add onewire node to ''fdt_overlays'' node if it doesn't exist.


e.g. To enable onewire, you need to add ''onewire'' to node ''fdt_overlays'' if it doesn't exist.

```shell
fdt_overlays=onewire

```

<tabbox VIM3L with 5.15 kernel>

Edit ''/boot/dtb/amlogic/kvim3l.dtb.overlay.env'' to add onewire node to ''fdt_overlays'' node if it doesn't exist.


e.g. To enable onewire, you need to add ''onewire'' to node ''fdt_overlays'' if it doesn't exist.

```shell
fdt_overlays=onewire

```

<tabbox VIM4>

Edit ''/boot/dtb/amlogic/kvim4.dtb.overlay.env'' to add onewire node to ''fdt_overlays'' node if it doesn't exist.


e.g. To enable onewire, you need to add ''onewire'' to node ''fdt_overlays'' if it doesn't exist.

```shell
fdt_overlays=onewire

```
<tabbox VIM1S>

Edit ''/boot/dtb/amlogic/kvim1s.dtb.overlay.env'' to add onewire node to ''fdt_overlays'' node if it doesn't exist.


e.g. To enable onewire, you need to add ''onewire'' to node ''fdt_overlays'' if it doesn't exist.

```shell
fdt_overlays=onewire

```
</tabbox>

<WRAP tip >
Reboot the system for this change to take effect.
</WRAP>


===== Get Sensor Data =====

Here we attach a 1-Wire device ''DS18B20'' temperature sensor to the 1-Wire bus.

Enter the driver directory:
```shell
khadas@Khadas:~$ cd /sys/bus/w1/devices
khadas@Khadas:/sys/bus/w1/devices$ ls
28-0119395ebf91  w1_bus_master1
```

You can see the node of ''ds18b20'' is ''28-0119395ebf91''. Enter this directory:
```shell
khadas@Khadas:/sys/bus/w1/devices$ cd 28-0119395ebf91
khadas@Khadas:/sys/bus/w1/devices/28-0119395ebf91$ ls
driver  id  name  power  subsystem  uevent  w1_slave
```

Read ''w1_slave'' file will get the temperature value:
```shell
khadas@Khadas:/sys/bus/w1/devices/28-0119395ebf91$ cat w1_slave
b1 01 4b 46 7f ff 0c 10 d8 : crc=d8 YES
b1 01 4b 46 7f ff 0c 10 d8 t=27062
```


===== Disable 1-Wire to Use GPIO =====

If you want to use normal GPIO instead of 1-Wire, you can remove the 1-Wire node in [[products:sbc:common:configurations:device-tree-overlay|Device Tree Overlay]].