Overview

amforth is a compact forth interpreter and compiler for the atmel avr atmega micro controller family. It is implemented in assembly language and forth itself. It is an interactive system runnung completly on the controller. It does not need additional hardware beyond a power supply. A (serial) terminal is a nice to have ;=)

amforth is published under the GNU Public License v2 (GPL).

amforth implements an ANS94 indirect threading 16bit Forth with very few missing CORE words, some words from the extension word sets and a few own words.

amforth can be downloaded from the project page.

Karl Lunt has written an excellent User guide on how to use and work with amforth. Thank you Karl! A more technical description is the Documentation (PDF, 6.5.2008). which is slowly growing.

News

• trunk

  • core: Bernard Mentink wrote a Atmega128 device file, Thanks alot.
  • core: Atmega88 & Atmega168 work well (arduino).
  • core: Fix regression for atmega128.
  • core: Moved serial interface words to application dictionary (not every amforth installation may have a serial terminal).

5.4.2007: release 2.7

• core, lib and sample applications are now in one package.
• restructured repository layout. Now the trunk has most of the sources.
• core: re-arranged the register mapping.
• core: m* was in fact um*.
• core: double cell numbers changed stack order: TOS is now the most significant cell.
• library: new: assembler written by Lubos Pekny, www.forth.cz. Thank you!

• 27.1.2008: release 2.6

  • core: new defining words code and end-code. code starts a new dictionary header with the XT set to the data field. The 2nd one appends the jmp NEXT call into the dictionary.
  • core: removed the pre-assembled case / endcase words. Added them as forth library.
  • core: new words -jtag (turns off JTAG at runtime) and -wdt (turns off watch dog timer at runtime. They need to be implemented as primitives due to timing requirements.
  • core: quit: Keep base when handling an exception.
  • library: TWI/I2C EEPROM Support.

• 6.12.2007: release 2.5

  • Bug: hex 8000 . froze the controller. Now it prints -8000. Thanks to Lubos for the hint.
  • Moved init of base from quit to cold. turnkey be used to change it permanently. Thanks to Lubos for the hint.
  • nice looking dumper words for RAM/EEPROM/FLASH, dropped idump.asm.
  • Extended Upload utility (tools/amforth-upload.py) from piix: include files using following syntax:

    		\ demo file
    		#include ans94/marker.frt
    		marker empty
    		

  • usart transmit (tx0) made more robust.
  • User Area restructured for the new multitasker.
  • added documentation: Karl's User guide and a Technical guide.

• 11.10.2007: release 2.4

  • Added AT90CAN128. Other Atmega128 style controllers should work too.
  • lot of fine tuning.
  • dropped the assembler device init portion.
  • New file: dict_compiler.inc. Without these words the forth system is (more or less) a pure interactive system without extensibility.
  • new words [char], fill.
  • re-arranged usart code. fixed bug when usart baud rate calculation leads to values greater 255.
  • renamed /int to -int and int to +int, it's more fortish ;=)

• 29.7.2007: release 2.3

  • new words spaces and place.
  • Improved i!.
  • bugfixing runtime parts of do/loop and co.
  • re-coded find and icompare for better readability.
  • eliminated code duplets in some primitives.
  • moved usart init from cold to application specific turn key action. Added error checking in receive module.

• 17.6.2007: release 2.2

  • new download section: application
  • optional dictionary is now part of the application, therefore renamed to dict_appl.
  • new words: leave and ?do.

• 22.5.2007 release 2.1

  • changed stack effect for # to ansi (from single cell value to double cell). Double cell values do not work (yet).
  • introduced deferred words instead of tick-variables. Works for EEPROM based vectors (turnkey), RAM based (PAUSE) and User based (EMIT etc) vectors.
  • new words: wdr (Watchdog reset), d> and d< (double cell compare).

• Older News

Notes

amforth uses the serial line uart0 (hard coded) as the terminal. Serial line settings are 9600 8N1, no flow control.

Development hardware is a evaluation board running varios atmega at 8 MHz or 16MHz with a few led's and pushbuttons. Targets for the final version are robots (asuro and ct-bot) and model railroad systems using atmega32 and atmega8. Some special notes for the Atmel Butterfly.

The source is developed with avra (linux) and sometimes debugged in the simulator from the AVR Studio 4.13 (Windows).

Known Bugs

These are known effects that one may call bugs for the lastest development revision (trunk). They may or may not get fixed for the next release(s).

• The following code does not work: : x0 ." " ; (compiling a string with len 0 (zero)). This is due to the fact that ." uses word internally which skips the leading characters used as delimiters. Thanks to Michael Kalus for this analysis.

• up to and including core version 2.6 double cell values have the order: TOS low part, NOS high part. Since 2.7 this is the other way around. You should always use s>d and d>s for conversion.

• The return stack has an off-by-one effect when using it's addresses:

  > : rstest 1234 >r rp@ @ . r@ . r> ;
   ok
  > rstest
   3405 1234 ok
  > : rstest2 1234 >r rp@ 1+ @ . r@ . r> ;
   ok
  > rstest2
   1234 1234 ok
  >    
  	    

• # has double cell stack effects but does not work with values beyond single cell.

Differences to ANS94

amforth has the following known differences to ans94. This list is not complete and the entries here are not considered bugs.

• +loop and loop assume signed values for both loop counter and loop limit.