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1-Wire interface

1-Wire is a device communications bus system designed by Dallas Semiconductor Corp. This article explains how to use it on the CM3-HOME-B and CM3-HOME-F boards

What is a 1-wire bus ?

The most popular use of 1-wire bus is to use the Dallas DS18B20 temperature sensors. The image below illustrates how to wire it on the screw terminals available on the CM3-Home board. It is possible to wire more than one sensor.

As depicted on the , the 1-wire data line is interfaced through a dedicated buffer in order to allow a more robust bus, therefore it doesn't require a pullup.


To use the 1-wire sensor port add this lines to config.txt file and reboot:

# Enable the 1-wire bus 

The sensor wired are automatically detected by the Linux Kernel and a new directory is created on the folder /sys/bus/w1/devices for each of them.

$ ls /sys/bus/w1/devices/

In this case a temperature sensor with id=28-000006c423d3 has been detected. To read the temperature value type:

$ cat /sys/bus/w1/devices/28-000006c423d3/w1_slave 
a4 01 4b 46 7f ff 0c 10 da : crc=da YES
a4 01 4b 46 7f ff 0c 10 da t=26250

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