A minimal Forth-like core for AVR (ATmega328P), designed to experiment with unified RAM and FLASH word handling using __memx pointers in C. This project should result in small tool for pin manipulation on both atmega328P and atmega2560. Based on memxFORTH-init
- Unified handling of dictionary words in both RAM and FLASH
- Explore low-footprint interpreter design in C
- Use __memx for flexible word list chaining and execution
- Small tool for HW testing - mainly pin manipulation
- Targets: atmega328P and atmega2560
- Dictionary traversal using __memx pointers / uint32_t
- Execution of basic hardcoded words in FLASH and RAM
- Basic words for building new words ( : ; CREATE )
- Basic structures ( IF ELSE THEN FI )
- debugging tools ( dump show noinfo nodebug )
- PORTx, PINx, DDRx for all x on platform
- Modular, small codebase suitable for embedded hardware debugging
- Uses C and AVR-GCC (also Arduino IDE compatible)
Compile as usual with avr-gcc, tested on ATmega328P.
Arduino IDE:
- Open memxFORTH-core.ino
- Select "Arduino Nano" with ATmega328P
- Upload as usual
- Developed for ANSI terminal on a wide monitor
- Serial speed: 115200 baud
- Colors can be disabled in colors.h
- After upload, the program: - Show some hints for copy-paste - Runs internal test on DOUBLE and show WORDS - Run classical loop on INTERPRETER
- This project is attempt to build small usable tool
- show (xt -- ) "disasseble" a word - ' DOUBLE show
- dump (Daddr -- ) dump some memory around given address - LATEST @ 20 - dump
- ff ( -- 0xFF ) - constant
- aa ( -- 0xAA ) - constant
- PORTx PINx DDRx - A..H on atmega2560 A..C on atmega328P - ff DDRD !C aa PORTD !C ff PINC !C
- nodebug (bool -- ) set debugging prints on(true)/off(false)
- noinfo (bool -- ) set info level on(true)/off(false)
- cw2h (Dcw -- Dh) convert pointer to codeword to pointer to head
- bin dec hex (--) set BASE to 2 10 16 respectively
- BRANCH 0BRANCH - branch, branch if zero - next field is offset in pointer increases - -2=prev instruction, -1=loop(self), 0=crash (jump inside instruction), +1=nop(next instruction), +2=skip next instruction
- WORDS2 - WORDS but in RAM
- ELSE THEN FI IF - THEN is synonymum for FI
- : ;
- HIDE (--) HIDE WORD hide given word
- HIDDEN (Daddr -- ) hide/unhide word at address
- QUIT - loops INTERPRETER
- <=0 <0 >=0 >0 !=0 ==0 - tests
- IMMEDIATE (Daddr -- ) make word at address IMMEDIATE
- ' - "TICK" read next word and push address of its codeword
- FIND (str n -- Daddr) find word in vocabulary
- ] (--) STATE=st_compiling
- [ (--) STATE=st_executing
- CREATE (str n --) create head from WORD result
- WORDS (--) print all words. Immediate words have red background, hidden words have grey text.
- INTERPRET - read word from input and execute it
- . (n -- ) print number
- NUMBER (str n -- num bad) decode string for number, return decoded number and count of unconverted chars
- , (Daddr--) - "COMMA" put address to *HERE and increments HERE
- WORD (-- str n) read word from input to data stack
- KEY (-- c) read character from input
- EXIT end words definition
- /4D (D -- D/4)
- /2D (D -- D/2)
- /D (D1 D2 -- D1/D2)
- *D (D1 D2 -- D1*D2)
- -D (D1 D2 -- D1-D2)
- +D (D1 D2 -- D1+D2)
- SWAP2 (D1 D2 -- D2 D1)
- DUP2 (D1 -- D1 D1)
- /4 (n -- n/4)
- /2 (n -- n/2)
- / (n1 n2 -- n1/n2)
- * (n1 n2 -- n1*n2)
- - (n1 n2 -- n1-n2)
- + (n1 n2 -- n1+n2)
- SWAP (n1 n2 -- n2 n1)
- DUP (n1 -- n1 n1)
- D@ (Daddr -- D) "DOUBLE AT"
- C@ (Daddr -- c) "Char AT"
- @ (Daddr -- n) "AT"
- !D (D Daddr --) "SET DOUBLE"
- !C (c Daddr --) "SET Char"
- ! (n Daddr --) "SET"
- LIT2 (-- D) push next pointer to datastack as DOUBLE
- LIT (-- n) push next pointer to datastack as single CELL
- DOCOL (-- &f_docol) constant = codeword for words
- BASE (-- Daddr) variable = numerical base
- STATE (-- Daddr) variable = STATE
- LAST (-- Daddr) variable = start of latest head
- HERE (-- Daddr) variable = first unused character in RAM
- PORTx DDRx PINx - addreses for pin manipulation (x=A..L for atmega2560, x=B..C for atmega328P)
GPL 2 or GPL 3 - choose the one that suits your needs.
Gilhad - 2025