amforth-devel

[Amforth-devel] Set hook from word / Timers / Praise!

[<ha...@hu...>]

Hi Matthias,

I have a forth and an amforth question:

On the web page, it is descibed that

' mypause 'pause !

sets the pause hook to the word mypause.  That works just fine from
immediate mode, but not from within another word.  How would I achieve
the same thing from within another word?

Also, on the home page under Bugs, "Using timer interrupt may cause
strange effects." is mentioned.  I would like to use a timer to
refresh my multiplexed LED display, can you let me know what the
"strange effects" are?

I love amforth!  Being able to iteratively develop on the AVR is so much fun!

Thanks!
Hans

Re: [Amforth-devel] Set hook from word / Timers / Praise!

[<ha...@hu...>]

2007/3/13, Hans H=FCbner <ha...@hu...>:
> On the web page, it is descibed that
>
> ' mypause 'pause !
>
> sets the pause hook to the word mypause.  That works just fine from
> immediate mode, but not from within another word.  How would I achieve
> the same thing from within another word?

I checked the ANS specification
(http://www.taygeta.com/forth/dpans.htm) and found the answer myself,
['] in a word definition does what ' does in immediate mode, so my
code now reads

: start-display ( -- )
    init-display
    0 set-display
    ['] refresh-display 'pause !
;

-Hans

Re: [Amforth-devel] Set hook from word / Timers / Praise!

[<ha...@hu...>]

2007/3/13, Matthias Trute <mt...@we...>:
> Hans H=FCbner wrote:
> > Also, on the home page under Bugs, "Using timer interrupt may cause
> > strange effects." is mentioned.  I would like to use a timer to
> > refresh my multiplexed LED display, can you let me know what the
> > "strange effects" are?
>
> If the frequency is too high (say 100Hz on a 16MHz controller) the
> controller stops responding. And regardless of the frequency you are not
> able to use the flash write operation i! and all words using it. I have
> no idea why it happens...

For fun, I have connected a four digit 7 segment display to my
ATMEGA32 running at 16 Mhz.  The display is multiplexed in two pairs,
so I need to refresh fast enough to get a stable display.  To do so, I
use TIMER0 with the overflow interrupt mapped to vector three.  I
prescale the timer by 256, thus my interrupt handler is called at
about 240 Hz.  It just works.  Also, I have observed no anomalies
working in immediate mode while my display refresh was active, so I
could still compile works.  What a gas!  Great stuff :)

-Hans

If anyone's interested:

I had to patch devices/atmega32.asm:

.org=09OVF0addr ; Overflow0 Interrupt Vector Address
    rjmp int3_isr

\ Ansteuerung der vierstelligen 7-Segment-Anzeige

\ Port A =3D> 1. und 3. Stelle
\ Port B =3D> 2. und 4. Stelle
\ Port C =3D> Bit 0: 1. und 2. Stelle ausw=E4hlen
\           Bit 1: 3. und 4. Stelle ausw=E4hlen
\           Bit 1 und 3 d=FCrfen nicht gleichzeitig auf 1 gesetzt werden!

decimal

\ Tabelle f=FCr die Umsetzung von Ziffern in Bits f=FCr die 7-Segment-Anzei=
ge

create 7seg-digit-map
 63 invert ,   6 invert ,  91 invert ,  79 invert ,
102 invert , 109 invert , 125 invert ,   7 invert ,
127 invert , 111 invert ,

\ Umrechnen einer Ziffer in Bits f=FCr die 7-Segment-Anzeige

: 7seg-digit ( n -- m )
    7seg-digit-map 1+ + i@
;

\ Variable f=FCr die aktuell angezeigten Display-Bits

0 variable display 3 allot

\ Eine Zahl ins Display-Register schreiben
: set-display ( n -- )
    4 0 do
        10 /mod
    loop
    drop
    7seg-digit display 3 + c!
    7seg-digit display 2 + c!
    7seg-digit display 1 + c!
    7seg-digit display     c!
;

\ Initialisieren der Schnittstelle zum Display
: init-display

    \ Erst mal die Bits so einstellen, da=DF alle LEDs aus sind
    255 PORTA c!
    255 PORTB c!
    0 PORTC c!
    \ Jetzt die Datenrichtungsregister setzen, so da=DF die
entsprechenden Bits alle
    \ als Ausgang konfiguriert sind.
    255 DDRA c!
    255 DDRB c!
    7 DDRC c!
;

\ Aktuell aktive Display-H=E4lfte
0 variable field

\ Wechseln der Display-H=E4lfte und anzeigen der passenden Ziffern.  Jedes
\ Mal, wenn das Wort refresh-display aufgerufen wird, wird wird das Display
\ umgeschaltet.  Wenn man refresh-display schnell genug hintereinander aufr=
uft,
\ ergibt sich ein stehendes Bild.
: refresh-display ( -- )
    0 PORTC c!
    field c@
    dup if
        display     c@ PORTA c!
        display 1 + c@ PORTB c!
        2 PORTC c!
    else
        display 2 + c@ PORTA c!
        display 3 + c@ PORTB c!
        1 PORTC c!
    then
    not field c!
;

\ Demo f=FCr refresh-display
: refresh-display-demo ( -- )
    begin
        refresh-display
        1ms
    key? until
    key drop
;

\ Anzeige aller vier Ziffern im Hintergrund.  Die Umschaltung erfolgt
\ durch den Timer-Interrupt.
: start-display ( -- )
    init-display
    0 set-display

    ['] refresh-display 3 intvector !

    \ Timer clock =3D> sysclk / 256
    4 TCCR0 c!
    \ Timer0 einschalten
    1 TIMSK c!
;

: count ( -- )
    10000 0 do
        i set-display
        1ms
    loop
;

Re: [Amforth-devel] Set hook from word / Timers / Praise!

[<ha...@hu...>]

Am 13.03.07 schrieb Hans H=FCbner <ha...@hu...>:
> For fun, I have connected a four digit 7 segment display to my
> ATMEGA32 running at 16 Mhz.  The display is multiplexed in two pairs,
> so I need to refresh fast enough to get a stable display.  To do so, I
> use TIMER0 with the overflow interrupt mapped to vector three.  I
> prescale the timer by 256, thus my interrupt handler is called at
> about 240 Hz.  It just works.  Also, I have observed no anomalies
> working in immediate mode while my display refresh was active, so I
> could still compile works.  What a gas!  Great stuff :)

Just an observation:  While compiling, the display flickers.  It seems
that IRQs are being disabled during flash programming, which is a good
thing.  Other than that, the timer driven refresh code has now been
running for several hours without a hitch.

-Hans

Re: [Amforth-devel] Set hook from word / Timers / Praise!

[Matthias T. <mt...@we...>]

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Hi Hans,

Hans H=FCbner schrieb:
> Am 13.03.07 schrieb Hans H=FCbner <ha...@hu...>:
>> For fun, I have connected a four digit 7 segment display to my
>> ATMEGA32 running at 16 Mhz.  The display is multiplexed in two pairs,
>> so I need to refresh fast enough to get a stable display.  To do so, I
>> use TIMER0 with the overflow interrupt mapped to vector three.  I
>> prescale the timer by 256, thus my interrupt handler is called at
>> about 240 Hz.  It just works.  Also, I have observed no anomalies
>> working in immediate mode while my display refresh was active, so I
>> could still compile works.  What a gas!  Great stuff :)
>=20
> Just an observation:  While compiling, the display flickers.  It seems
> that IRQs are being disabled during flash programming, which is a good
> thing.

This is really a good news. In my tests the controller always
freezes when the flash gets written. I should re-do the tests...

Thanks+Bye
Matthias

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