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Table of Contents
1-Wire
Introduction
This document mainly introduces the usage of 1-Wire bus on 40-Pin Header.
1-Wire Information
You can find the default PIN used for 1-Wire bus from the table below.
| PIN | GPIO(#number) | DT Overlays Node | Device Node | |
|---|---|---|---|---|
| VIM1/2 | 37 | GPIOH_5(#421) | onewire | /sys/bus/w1/devices |
| VIM3/3L | 15 | GPIOH_6(#433) | ||
| VIM4 | ||||
| Edge1 | 30 | GPIO4_A0 |
Enable 1-Wire Bus
In order to use the 1-Wire, you need to enable the 1-Wire function via Device Tree Overlay.
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.
overlays=onewire
VIM4
Edit /boot/dtb/amlogic/kvim4.dtb.overlay.env to add onewire node to fdt_overlays node if it doesn't exist.
e.g. Enable onewire, you need to add onewire to node fdt_overlays if it doesn't exist.
fdt_overlays=onewire
Reboot to effect.
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 device tree overlays configration file.
Get Sensor Data
Here we attach a 1-Wire device DS18B20 temperature sensor to the 1-Wire bus.
Enter the driver directory:
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:
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:
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