When I recently ordered some stuff from an Amazon dealer, I saw, that he offered LCD displays like that from the "I2C LCD Kit" for just 3€. So I could not resist and ordered three.
I knew, that they had no I2C backpack, but I remembered that in the info-directory of the DigisparkLCD library there was a schematic diagram, how the display should be connected.
Unfortunately that picture showed a possible wiring, which is however incompatible with the digisparc library.
So I unsoldered the backpack from my official shield and did some reverse engineering.
In the picture from the library, they have changed the lower and higher nibble of the 8 data ports from the PCF8574:
They are referring:
Pin 4-7 -> LCD Pin11-14 (4-bit data)
Pin 9-11 -> LCD En/RW/RS
Pin 12 -> backlight (with pnp-transistor)
The backpack from the official shield connects:
Pin 4-6 -> LCD RS/RW/En
Pin 7 -> backlight with npn-transistor
Pin 9-12 -> LCD Pin11-14 (4-bit data)
The following schematic works with the digisparc library. I combined the I2C pullups from the shield into that schematic. With this backpack you should be able to connect all 1-4 line HD44780 compatible displays to the digisparc.
http://en.wikipedia.org/wiki/Hitachi_HD44780_LCD_controllerAlmost all character-displays are descendants of that controller. It looks like, that in the arduino world there are several I2C backpacks around, which makes I2C enabled displays depended from the used serial/parallel converter and wiring.
@Erik feel free, to include my picture into the DigisparkLCD library.
regards
gogol
