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OneWire Library

This is just a mirror from Teensyduino

OneWire lets you access 1-wire devices made by Maxim/Dallas, such as temperature sensors and ibutton secure memory. For temperature sensors, the DallasTemperature library can be used in conjunction with this library.

The DS18x20_Temperature has a known bug. Remove "unsigned" from the raw variable on line 88, for correct results below zero degrees Celsius!

Hardware Requirements

OneWire requires a single 4.7K pullup resistor, connected between the pin and +5 volts. Then just connect each 1-wire device to the pin and ground. Some 1-wire devices can also connect to power, or get their power from the signal wire. Please refer to the specifications for the 1-wire devices you are using.

Basic Usage

OneWire myWire(pin);

Create the OneWire object, using a specific pin. Even though you can connect many 1 wire devices to the same pin, if you have a large number, smaller groups each on their own pin can help isolate wiring problems. You can create multiple OneWire objects, one for each pin.

myWire.search(addrArray);

Search for the next device. The addrArray is an 8 byte array. If a device is found, addrArray is filled with the device's address and true is returned. If no more devices are found, false is returned.

myWire.reset_search();

Begin a new search. The next use of search will begin at the first device.

myWire.reset();

Reset the 1-wire bus. Usually this is needed before communicating with any device.

myWire.select(addrArray);

Select a device based on its address. After a reset, this is needed to choose which device you will use, and then all communication will be with that device, until another reset.

myWire.skip();

Skip the device selection. This only works if you have a single device, but you can avoid searching and use this to immediatly access your device.

myWire.write(num);

Write a byte.

myWire.write(num, 1);

Write a byte, and leave power applied to the 1 wire bus.

myWire.read();

Read a byte.

myWire.crc8(dataArray, length);

Compute a CRC check on an array of data.

1-Wire Information

History & Credits

  • Jim Studt wrote OneWire in 2007, originally based on code by Derek Yerger.
  • Tom Pollard added CRC code which eliminated the need for a 256 byte array (in RAM).
  • "RJL20" added the skip function.
  • Robin James rewrote the search function, posting his version here.
  • Paul Stoffregen rewrote the I/O routines for interrupt safety, replaced search with Robin James's code, applied several small optimizations, and started calling it "version 2.0" to distinguish from the many buggy copies online.