Hello,
did you ever try the multitasker, that is included with amforth?
It did work, however, it did not survive switching power off and on
again.
Matthias Trute and I have spent some effort to fix this and change
the implementation accordingly. So please find the following new
items:
1. a new version of trunk/lib/multitask.frt
http://amforth.svn.sourceforge.net/svnroot/amforth/trunk/lib/multitask.frt
this will be included in release/4.7 and later.
Changes:
- address of the task control block and stack
sizes are now stored permanently in flash.
- task-init will recreate the task control block
in RAM from scratch. Typically this would be used
in a "starttasker" or similar word (see below).
2. a piece of detailed documentation at
http://amforth.sourceforge.net/recipes/single_multitasker.pdf
This explains in considerable detail, how the multitasker works.
It includes example code and a commented version of multitask.frt
3. Example code
included below in this post. This will be added to the repository
as well.
Feel free to test and use this. Comments and questions are
definitely welcome.
We are aware that the implementation of the multitasker
can be moved into the amforth core and changed in such a way
that the programmer hardly notices it's there. However, we
decided to release this and see, if anything else is needed.
Thanks to Matthias and the nice folks on
irc.belwue.de #forth-ev (german irc) for help in various ways.
Cheers,
Erich
--- example code -----------------------------------------------------
\ run_multitask -- tested with amforth-4.7, atmega-32
$38 constant PORTB
$37 constant DDRB
include lib/multitask.frt \ load the multitasker
: ms ( n -- ) 0 ?do pause 1ms loop ; \ call pause on wait
variable N
: init
$ff PORTB c! \ portB: all pins high
$ff DDRB c! \ all pins output
0 N !
;
: run-demo \ --- task 2 ---
begin
N @ invert PORTB c!
1 N +!
&500 ms
again
;
$20 $20 0 task: task_demo \ create task, allot tcb + stack space
: start-demo
task_demo tcb>tid activate
\ words after this line are run in new task
run-demo
;
: starttasker
task_demo task-init \ create TCB in RAM
start-demo \ activate tasks job
onlytask \ make cmd loop task-1
task_demo tcb>tid alsotask \ start task-2
multi \ activate multitasking
;
: run-turnkey
applturnkey
init
starttasker
;
' run-turnkey is turnkey \ make run-turnkey start on power up
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