FAQ

Where do I find more information?

There are 2 documentation files: a User’s Manual written by Karl Lunt and a more Technical Guide.

A lot of information is in the cookbook. There you can find many small recipes on a specific topic. Most of them can be combined.

More can be found in the Maillinglist archive

How do I start with amforth?

First: You will have to build your own amforth first. To do this you really want to make copy of the appl/template directory and edit the files in it to fit your environment: controller type, cpu frequency, serial port settings etc. The files are well documented. Once the assembler produces two hex files and no errors (warnings should not come up either) you can proceed. If you are using the Atmel studio, make sure that the project settings include the generation of the eep files. This settings may be disabled by default.

Second you need a programmer to transfer the hex files you generated to the controller. The only programmers that can be used are those that can work on bare (micro controller) systems: ISP (e.g. the Atmel AVRISPmk2 or stk200 or ponyser), JTAG (e.g. the AVR Dragon), High Voltage programming (rarely used) or DebugWire (same: rarely used). Programming tools that relies on a boot loader on the micro-controller itself can not load amforth (the reasons are explained in the Technical Guide.

The program to talk with the programmer is avrdude. It is a swiss army knife like tool, that works for almost all devices on all operating systems (Linux, Windows, MacOS and few more). The Makefiles / ANT files use it. Other programs (just like the famous Atmel Studio) are never used by me, you are on your own.

After you transferred “burned” both hex files (one for the flash memory, one for the EEPROM memory), you can begin working with amforth on the serial connection.

How do I use amforth interactively?

At the command prompt you can enter any command and can explore the controller. To simply add two numbers just do the following:

> 24 42 + .
66 ok
>

To get the content of an IO register just use the memory mapped address (the example reads the 16bit return stack pointer which the just the normal mcu stack pointer):

> $5d @ .
1101  ok
> rp@ .
1101  ok
>

8bit registers just use the c@ command instead of the @. Writing to any address is just as simple:

> 17 pad !
 ok
 > pad @ .
 17  ok
 >

What means ??

At the terminal prompt the ?? means that an error occured. If it is displayed, the normal interpreter command prompt got active. Interrupts will continue to work. It is followed by at least one number, if the error occures during a commoand session a second number may appear.

The first number is the error code. Technically it is a negative number. The numbers are in fact an exception code, that is not handled. The standard systems uses a few of them.

The second number is the position in the current input line at which the error has been detected. E.g. when the error code is -13 (not found), the second number points to the last character of the word that could not be found.

There are no hexfiles in the distribution archive!

Hex-files are very specific to the hardware, even the change of the oscillator frequency needs a rebuild. And every processor wants its own settings. There would be far too many different hex-files. For some targets a hex-file is provided (e.g AVR Butterfly).

I get no serial prompt!

You need to program two hex files, one for the flash memory and one for the EEPROM. The makefiles do that already automatically.

Next check are the frequency settings. Atmegas need a configuration (fuse setting) to use an external clock source. By default they run with an unstabilized 1MHz internal clock source, which is not well suited for serial communication. Check the datasheet of your controller to find the correct fuse settings, they are different for different atemgas and very sensitive, be absolutly careful! Rebuilt the hex files with the proper frequency (F_CPU setting).

Finally check the terminal settings: For the AVR devices the default settings come from the file preamble.inc and are set to 38400 8N1, no flow control. It is possible and the preferred way to overwrite these settings in you application setup file. Some example application do so. The MSP430 defaults (9600 8N1) are hard coded inside the device settings and cannot be changed easiely (currently).

Finally check the hardware. You may add a LED (or a scope) to the TX pin to check wether the controller sends out the boot message upon reset. Plug off all programmers (they may keep the RESET pin).

Check the mailing list archive for other hints or (finally) ask there for help.

What do all the words do?

amforth tries to implement the Forth 2012 dialect of forth. The last public version is available at (e.g.) Taygeta Archive

I miss a word!

The default configuration includes most but not all words. A few words are written in assembly and can be found in the platform/words directory. The file names usually reflect the forth names. If you need on of those words, you’ll have to edit your project files and recompile amforth. A lot more words are available as forth code. To use them you only need to send the forth code to the controller. The Amforth-Shell may become your friend for that.

Can I embed amforth into other programs?

Embedding amforth into other programs (e.g. written in C) is almost impossible. Amforth is designed to run stand-alone and does not follow any conventions that may be used on other systems.

Can I use code written in C (or any other language) with/in amforth?

Short answer: no.

What means the GPL for my programs?

As long as you don’t use your (Forth) program with amforth: Nothing. It’s your code and you decide everything.

If you combine your code with amforth, the result is GPL licensed, no matter what you think about it. That means your users (sometimes called customers or business partners) have access to your code together with amforth under the GPL. It doesn’t matter whether you use the GPLv2 (older versions of amforth) or newer ones. I kindly ask these users to send me a copy.

Why should I send you my code?

Really simple: I want to improve amforth. The best way to do so is to study code using it. That includes ports of modules to other Forth’s.

Does amforth run on hardware xy?

amforth is targeted to Atmel AVR Atmega controllers. It does not and never will run on Attiny controllers or on completely different architectures like PIC or 8051 etc. Work is currently under way to port to the Texas Instruments MSP430.

What about the fuses?

Just set them to the factory defaults and adjust the oscillator settings only. amforth uses the self programming capabilities so if any boot loader works, amforth should do so. Make sure that the boot loader size is as large as the NRWW flash size, otherwise the flash write operation may fail silently and crash your system completely.

What about boot loaders?

amforth overwrites them, they are no longer existent. And this can only be changed for boot loaders with an application usable API to use the flash self programming feature. There are none currently available. With such an API the only word that’s need to be rewritten is !i.

What do I need for linux?

The linux assembler avra comes without the controller definition files. They need to copied from the Atmel AVR Studio. Please use the version 1 of the files from the AvrAssembler/appnotes directory. The Makefiles in the applications expect the files in the directory ~/lib/avra. Please note that these files are horribly outdated and do not cover all controller types. For those controllers you need the Atmel AVR Assembler version2. See next note.

How do I use Atmel’s assembler with linux?

First you need a working setup of a recent wine. Then put the avrasm2.exe and the Appnotes directory somewhere on your system. Then edit the makefile to look similiar too:

AVRDUDE=/usr/local/bin/avrdude

PP=-c stk200  -P /dev/parport0
JTAG=-c jtag1 -P /dev/ttyUSB2

AVRASM=wine ~/projects/avr/AvrAssembler2/avrasm2.exe
AVRASMOPTS=-fI -I ~/projects/avr/AvrAssembler2/Appnotes -e $@.eep -l $@.lst -m $@.map

p8.hex: *.asm words/*.asm devices/*.asm
  $(AVRASM) $(AVRASMOPTS) p8.asm

p8: p8.hex
  $(AVRDUDE) $(PP) -p atmega644 -e -U flash:w:p8.hex:i -U eeprom:w:p8.hex.eep:i

please note that the file names are slightly different from the avra generated code. Good luck.

What resources are available in my own assembly words?

You can use any resource if you take care. There are some things you need to obey: Never use the T flag in the machine status register SREG. Only the CPU registers named temp0..temp5 are save to use without the need of restoration. Any other register change may be harmful.

What is the release policy?

Releases are made when there are ready. Usually the list of changes is limited to only a few things. Every release is considered stable and ready for production use. The version number gets increased by 0.1 with every release. That means, that a .0 release is nothing special.

How do I send forth code to the system?

Basically send them as ascii text via the terminal line. A command line like:

> ascii-xfr -s -c 10 -l  100  devices/atmega32.frt > /dev/ttyS0

can be used. amforth does not currently support any kind of flow control. Any transfer has to be slow enough to not overrun the buffers. A more sophisticated approach is described in Use of the amforth-shell.py utility

I found a bug

Too bad. Please send all information to the Mailling List