A forth implementation for rp2040. Inspired by (obvious if one read the code) - but not a port of - jonesforth.
It will likely never be "complete" - the primary purpose is as a vehicle for me to learn arm (+ rp2040= assembler.
Yes, and lots of them.
Notably, there is no error handling at all. This is by design (as in - I haven't gotten around to fixing it yet). Use an SWD adapter (picoprobe, jlink, ...) with gdb to avoid having to pull the plug all the time. You want one anyway, it makes life easier.
It also hangs when using USB for serial. No idea why. I use an UART adapter when developing and haven't prioritized a fix.
In progress, which is the reason for the switch to platformio from the rp2040 SDK. Prints things, creates words, freezes :-)
| Word | Description | Example |
|---|---|---|
| ." | Print a string terminated with ". Includes final space before last " in output. | ." banana!" |
| SPACE | Print a single space | |
| CR | Print a single newline | |
| CONSTANT | Create a constant from the first value on the stack. Returns its value when called. | 10 CONSTANT TEN TEN . |
| VARIABLE | Create a variable. Returns its address when called | VARIABLE ANSWER ANSWER 42 ! ANSWER @ . |
| BEGIN | Start a BEGIN-UNTIl loop. Compile only | : A 10 BEGIN DUP . 1 - DUP 0 < UNTIL ; A |
| UNTIL | Finish a BEGIN-UNTIL loop. Compile only. Loops until TRUE on top of the stack | See "BEGIN" |
| OVER | Copies the second-from-the-top stack value to the top: w1 w2 – w1 w2 w1 | |
| 0>=, 0>, 0<>, 0<=, 0<, <>, >=, <=, 0=, =, >, < | Various comparisons. See the gforth manual | |
| NOT | Inverts (boolean) the top word on the stack | 1 NOT . |
| MOD | Modulo | 5 3 MOD . |
| / | Division | 6 2 / . |
| /MOD | Div-Mod. a b -- a%b a/b | 6 2 MOD . |
| - | a b -- a-b | 6 2 - . |
| +, * | ||
| INTERPRET | The main loop, starts through the boot sequence and keeps restarting itself until the processor crashes | |
| NOP | No operation | |
| EXECUTE | Broken at the moment | |
| FIND | Find a word from a string pointer/length on the stack. pointer length -- pointer | (Doesn't work) WORD WORDS FIND DROP TYPE |
| RESET | Sometimes restarts the machine correctly. | |
| ROT | x1 x2 x3 -- x2 x3 x1 | |
| DROP | Removes the topmost value from the stack | |
| SWAP | Swaps the two topmost stack values | |
| DUP | Copies the topmost stack value | |
| WORDS | List all words | |
| BASE | Variable controlling the output and input number base. Max radix is 36. 0 is rejected. 1 might give interesting results. | 16 BASE ! 128 a base ! . |
| TYPE | Prints the null-terminated string pointed to by the top of the stack | |
| EMIT | Print the character on the top of the stack | 13 EMIT |
| . | Print the number on the top of the stack | 42 . |
| WORD | Read a word from input. Put a pointer to the string on the top of the stack. Non-persistent | |
| READ-LINE | Reads a line from input and updates the buffer. Useless at the moment | |
| FLUSHSTDIN | Used by the inner loop to clean out cruft from the serial port | |
| KEY | Read one character from the current input buffer | |
| S" | Compile a string to the next free memory. | |
| SKIPSTRING | (Invisible) Helper word to use compiled strings within a compiled word without crashing | |
| [ | Leave compile mode | |
| ] | Enter compile mode | |
| IMMEDIATE | Mark the last created word as immediate | |
| SEE | Decompile (sort of...) a word | SEE A |
| A | Demo word counting down from 10 to 0 | A |
| IF - ELSE - THEN | See [gforth docs}(http://www.complang.tuwien.ac.at/forth/gforth/Docs-html/Selection.html) | |
| BRANCH | Jump to the next execution address as specified in the word in the execution list directly after BRANCH | |
| 0BRANCH | As branch, but only if the top word on the stack is zero | |
| ! | Stores a value in a variable | 16 BASE ! |
| @ | Fetches a value from a variable | BASE @ . |
| HERE | Returns the address to the first free word in the memory | |
| LIT | Indicates that the next word in the execution list is a literal | LIT ' LIT |
| ALIGN | Align the free memory pointer to instruction boundary. Typically good to do if it is in risk of misalignment | |
| c, | Compiles a byte to the end of the memory and increases the free memory pointer with 1 | |
| , | Compiles a word (alignment-safe) to the end of the memory and increases the free memory pointer with 4 | |
| LATEST | Return the pointer to the last defined word and puts it on top of the stack | |
| ; | End of word declaration | : A ." A " ; |
| : | Start of word declaration | : A ." A " ; |
| ' | Interpreter: search for the next word in the stream, put the pointer on the stack (or 0 if failed). Compiler: compile the address of the next word in the stream. Used to compile a word instead of executing it in immediate mode |
|
| HIDDEN | Hides the last created word from FIND | |
| CREATE | Creates a forth header in the word list | |
| STATE | Constant indicating if we are in interpreter mode (0) or compile mode (1) | |
| DEBUG | Variable to enable (1) / disable (0) debug printouts | 1 DEBUG ! |
| SP0 | Constant: The initial value of the stack pointer | |
| SP@ | Constant: The current value of the stack pointer | |
| DEPTH | Constant: The depth of the stack before DEPTH is run | |
| R> | Move top of return stack to top of value stack | |
| >R | Move top of value stack to top of return stack |