Example code on how to connect a HD44780 or compatible LCD display to an amForth powered device
This is my first attempt on writing Forth code to interface an HD44780 based LCD to an Arduino running AmForth. For now, the pin setup is hardwired to the scheme shown below, but this will be changed in a future version. The code is tested with AmForth 5.7, the Forth kernel is build with the following dict_appl.inc:
; this dictionary contains optional words
; they may be moved to the core dictionary if needed
.include "dict/compiler2.inc" ; additional words for the compiler
.include "words/applturnkey.asm"
;; provide .s for interactive debugging
.include "words/dot-s.asm"
;; the following are needed to get the LCD code running
.include "words/edefer.asm"
.include "words/ms.asm"
The base ideas for the forth code came from an article at http://www.mikrocontroller.net. I just adapted their assembler code to Forth.
The LCD will work in 4bit mode, with the following connections:
| Display Pin | Atmega Pin | Arduino Name |
|---|---|---|
| D7 | PD7 | Digital 7 |
| D6 | PD6 | Digital 6 |
| D5 | PD5 | Digital 5 |
| D4 | PD4 | Digital 4 |
| Enable (E) | PD3 | Digital 3 |
| RS | PD2 | Digital 2 |