1-Wire

1-Wire is a device communication bus that provides low-speed data over a single conductor. It is also possible to power some devices over the data signal as well, but often a third wire is run for power.

Simple IoT supports 1-wire buses controlled by the 1-wire (w1) subsystem in the Linux kernel. Simple IoT will automatically create nodes for 1-wire buses and devices it discovers.

Bus Controllers

Raspberry PI GPIO

There are a number of bus controllers available but one of the simplest is a GPIO on a Raspberry PI. To enable, add the following to the /boot/config.txt file:

dtoverlay=w1-gpio

This enables a 1-wire bus on GPIO 4.

To add a bus to a different pin:

dtoverlay=w1-gpio,gpiopin=x

A 4.7kΩ pull-up resistor is needed between the 1-wire signal and 3.3V. This can be wired to a 0.1" connector as shown in the following schematic:

See this page for more information.

1-Wire devices

DS18B20 Temperature sensors

Simple IoT currently supports 1-wire temperature sensors such as the DS18B20. This is a very popular and practical digital temperature sensor. Each sensor has a unique address so you can address a number of them using a single 1-wire port. These devices are readily available at low cost from a number of places including eBay -- search for DS18B20, and look for an image like the below: