User manual

1-Wire Application Guide v1.04 Page 6 of 41
2 1-Wire Installations
2.1 1-Wire – What is it?
1-Wire® was a system originally developed by Dallas Semiconductor, now
Maxim, to provide an easy way to communicate between microprocessors and
peripheral devices using a minimum pin count, hence 1-Wire. 1-Wire devices
only require 1 microprocessor pin, and a common ground connection, to achieve
bi-directional communication. The 1-Wire system is sometimes also called
MicroLAN, or iButton®.
The original concept was to provide simplified communications on a single PCB
(Printed Circuit Board). With the release of several Sensors Magazine articles by
Dallas Semiconductor’s Dan Awtrey in the late 1990’s (see References),
however, 1-Wire became a very popular method of providing remote, in other
words, off-PCB, sensor data to a microprocessor. This popularity extended to
weather station monitoring, which is where TEMP08 has its roots.
Without getting too technical, since there are many white papers that get into the
technical details already, 1-Wire provides a way of powering and communicating
bi-directionally to remote sensors using only two wires, DQ and Ground. Sensor
types are discussed later in the guide.
1-Wire powering can be done “parasitically”, that is, at the same time as
communications. This is possible since the sensors store the received logic 1
signals as power whenever they are received.
2.2 Types of 1-Wire Networks
As for any other kind of network, there are different topologies possible. The two
main 1-Wire network types are bus and star.
2.2.1 Bus Network