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SoftWire

Introduction

SoftWire is a software I2C implementation for Arduino and other Wiring-type environments. It utilises the pinMode(), digitalWrite() and digitalRead() functions. The pins to be used for the serial data (SDA) and serial clock (SCL) control lines can be defined at run-time. Alternatively it is possible to override the functions which control the SDA and SCL lines, and read SDA and SCL, thereby allowing direct port manipulation to be used if preferred.

Multiple objects (for multiple software I2C buses) and clock-stretching by slave devices are supported. A timeout feature is included to prevent lockups by faulty or missing hardware. The microcontroller must function as the master device and multiple masters are not supported.

Low-level functions can be used to send start, and stop signals, and to read and write data; no buffers are required. In addition high-level functions provide almost direct compatibility with the Wire library. However, the user must first declare transmit and receive buffers, and configure SoftWire to use them before the high-level functions beginTransmission(), endTransmission(), read(), write() and requestFrom () can be used. Notify SoftWire of the buffers by calling the setTxBuffer() and setRxBuffer() functions, passing in a pointer to a byte or character buffer and the size of the buffer. See the ReadDS1307 fort an exmaple of how this is done.

It is possible to assign (and reassign) the pins associated with SCL and SDA at run-time using the functions setScl() and setSda().

Important changes for users of the v1.* library

To support the high-level functions required for compatibility with the Wire library the original low-level write() function has been renamed llWrite().

The setter functions setSdaLow(), setSdaHigh(), setSclLow(), setSclHigh(), setReadSda(), setReadScl() must be used to override the functions which control and read the SDA and SCL signals.

The functions which actually set SCL/SDA low/high are now named sclLow(), sdaLow(), sclHigh() and sdaHigh(). These functions should not be called directly in normal use but may be required to force some devices into low-power mode.

License

The SoftWire library is licensed with the GNU Lesser General Public License. See LICENSE.txt for details.

Requirements

The AsyncDelay library is required, see https://github.com/stevemarple/AsyncDelay

Contributors

• Steve Marple
• Matthijs Kooijman
• Phonog
• Tutoduino
• Brian Park
• Wayne Piekarski
• nerdyscout

Credits

This library is inspired by Peter Fleury's i2cmaster library.