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The SPI_LCD board
The SPI_LCD board

This is the documentation page for the I2C_LCD board.


Assembly instructions

The board comes fully assembled.

Possible Configurations

The board can also be configured for SPI operation.

The second SPI port can be used as an ICSP connector by changing a solder-jumper.

External resources


The fet: http://www.irf.com/product-info/datasheets/data/irlml2244pbf.pdf

The CPU: http://www.atmel.com/dyn/resources/prod_documents/doc8006.pdf

Additional software

Related projects


The board has two SPI connectors that are not populated and should not be used in the I2C version. SPI connector pinout The board has two I2C connectors. I2C connector pinout


none. (A future version will have a powerled).

Jumper settings

There are two solder jumpers. The one between the two 6-pin SPI connectors controls the function of the SPI connector furthest from the CPU.

In the non-default configuration, the second SPI connector is the ICSP connector.

The second solder jumper connects "rs" and "vo" of the LCD together (and to one pin of the attiny44 controller on the board) in the default configuration.
In the other configuration, the pin used for SPI slave select can be used as the RS pin. This could be used in the the I2C configuration, but to keep the software simpler this is not done.

There is a 10 mil (very small) PCB trace in the solder jumper in the default configuration. You'll have to cut this trace to move the solderjumper to the other position. If you later decide you want the other configuration again, some solder-wick can be used to remove the solder from one position and then it can be added to the other position.


To display things on the LCD, you need to send things over the I2C bus to the PCB. The protocol is explained here. If you have an older version, 1.2, the protocol is explained here

An example application is called "demo_lcd" and is available at [the bitwizard software download directory] . This appplication was written for the ftdi_atmega board from bitwizard, but can also be used on an arduino. But you'll have to download the hex to your board by hand after compiling.

For arduino, a sample PDE is available, called ar_i2c_lcd_demo.pde, also at [the bitwizard software download directory] .

The software

Future hardware enhancements

Future software enhancements

  • Lock the address. (require a sequence of commands to change the address).
  • Allow setting of the current eeprom address.
  • Allow reading/writing of the eeprom.



  • Initial public release