m4k3r-org / tinylcd_i2c

Firmware for LCD I2C backpack based on ATtiny84

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:

{
  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.

BOM

THT-Board:

• 220nF Cer Cap
• 100k(R4), 4.7k(R2), 150R(R3)
• ATtiny84A-PU
• 14 Pin DIP socket (optional)
• Header female (16pins)
• 2x3 Pin Header male

SMD-Board:

• 220nF Cer Cap
• 100k, 1k, 150R
• ATtiny84-SU (SOIC)
• Header female (16pins)
• 2x3 Pin Header male

Forum / contact

Issues around the tinyLCD_I2C board and firmware can be discussed 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