tinyLCD_I2C/README.md

tinyLCD_I2C
===========

Description:
------------
tinyLCD_I2C is a Firmware for LCD I2C backpack based on ATtiny84 with an Arduino library as drop-in replacment for the LiquidCrystal library.

Instructions
------------
Please make sure to use the TinyWireS library from this repo with the ATtiny implementation from
http://code.google.com/p/arduino-tiny/

Also you should make the following change in ./hardware/tiny/cores/tiny/wiring.c to improve performance of the TinyWireS library:

```ISR(MILLISTIMER_OVF_vect)
{
  sei();
  // copy these to local variables so they can be stored in registers
  // (volatile variables must be read from memory on every access)
```
Basically add the line
```  sei();```
to the ISR(MILLISTIMER_OVF_vect) function so that it looks like above excerpt.

See http://forum.boxtec.ch/index.php/topic,2225.msg2845.html#msg2845 for a discussion on this issue.

Boards / PCBs
-------------
The boards directory contains a Fritzing THT design on which current development is based and an Eagle 6.x SMD design which is currently in production for first prototypes.

Forum / contact
---------------
Issues around the tinyLCD_I2C board and firmware can be discuess here:
- http://forum.boxtec.ch/index.php/topic,2225.0.html

Credits
-------
Credits go to ..

.. brohogan for bringing the TinyWireS library to life in the first place.

.. pylon for fixing all the timing issue and race conditions in above library and enhancing the tinyLCD_I2C greatly (i.e. by adding SPI)

.. MathiasW for adding a SMD design with reduced size