aboudou / tinywiremcp23008

TinyWireMCP23008 is a library that ease the use of the MCP23008 I²C port expander with an ATtiny85 microcontroller.

ArduTemperatureMonitor

TinyWireMCP23008 is a library that ease the use of the MCP23008 I²C port expander with an ATtiny85 microcontroller.

• Project's page

Sources

TinyWireMCP23008 use multiple libraries:

• TinyWireM.* and USI_TWI_Master.*: comes from http://playground.arduino.cc/Code/USIi2c, and slighty modified to work on a 8 MHz ATtiny85 and with Fast Mode I²C.
• TinyWire_MCP23008.*: comes from https://github.com/adafruit/Adafruit-MCP23008-library, and adapted to work with TinyWire instead of Wire library.
• TinyWireMCP23008.ino: simple example to show how to use TinyWireMCP23008.

ATtiny85 frequency and I²C bus mode

TinyWireMCP23008 was tested (and works) with a 8 MHz ATtiny85 and I²C standard bus mode and I²C fast bus mode.

TinyWireMCP23008 was not tested with ATtiny85 other frequencies, but should work (I can't guarantee that fast bus mode will work with a 1 MHz ATtiny85).

TinyWireMCP23008 should work with other ATtiny microcontrollers.

If your ATtiny does not run at 8 MHz, you have to adapt the following line into USI_TWI_Master.cpp:

#define F_CPU 8000000UL

(Example : #define F_CPU 1000000UL for a 1 MHz ATtiny85)

If you want to disable I²C fast bus mode, you have to comment the following line into USI_TWI_Master.h:

#define TWI_FAST_MODE

You can find all the schematics for the provided example into “doc/TinyWireMCP23008.fzz”, to open with Fritzing.

The breadboard assembly and schematics