amforth-devel

[Amforth] Question about Timer1 - is there a bug?

[Jan K. <kro...@ho...>]

Hi,

I have taken the TIMER_1 example, and make some small change.
Instead of the timer1.tick I toggle pin-7 of the Arduino.
With the values as in the listing I measure a frequency of 15,2 Hz with my scoop.

When I change some of the preload value by hand no change is seeing.
Frequency is staying at 15,2 Hz.

When I print the value of TCNT1 after setting, and compare this one after
timer1.start there is a difference

First value = 63536 and the Second value = 31033.

I think some where in amForth TCNT1 is overwritten!

Please can you take a look.

I included my program.

Cheers,

Jan

\ TIMER1_interrupt

marker --timer1_interrupt--

PORTD 7 portpin: PD7
PD7 pin_output

&26 constant TIMER1_OVFAddr

: togglePD7
   PD7 pin_high? if PD7 low else PD7 high then
;

: timer1.isr
  \ toggle output PD7
  togglePD7
;

\ preload for overflow interrupt every 1 ms
\ preload = 65536 - (f_cpu / (prescaler * 1000))

: timer1.preload
   f_cpu #1000 um/mod nip 8 / negate  \ <===== if i change the value #1000 notting is change
;

: timer1.init ( -- )
    timer1.preload TCNT1 !
    TCNT1 @ u. cr   \ <===============  print value of TCNT1 ===========
    ['] timer1.isr TIMER1_OVFAddr int!
;

: timer1.start
    -int
    timer1.init
    %00000010 TCCR1B c! \ prescaler 8
    %00000001 TIMSK1 c! \ enable overflow interrupt
    +int
;

: timer1.stop
   %00000000 TCCR1B c! \ stop timer
   %00000000 TIMSK1 c! \ stop interrupt
;

Re: [Amforth] Question about Timer1 - is there a bug?

[Tristan W. <ho...@tj...>]

Jan,

> I think some where in amForth TCNT1 is overwritten!

Indeed. Every time timer1 overflows. 

> When I change some of the preload value by hand no change is seeing.
> Frequency is staying at 15,2 Hz.

Yes. You are seeing a frequency of

16000000 divided by 8      (for the prescaler)
         divided by 65536  (for each rollover of the timer1)
	 divided by 2      (for the LED toggle)

which gives a theoretical 15.3Hz , close to your observed value.

Are you looking to generate something for multiplexing a display?
There might be an easier way, if that is the case.

Best wishes,
Tristan

On 02Nov18 20:09, Jan Kromhout wrote:
> Hi,
> 
> I have taken the TIMER_1 example, and make some small change.
> Instead of the timer1.tick I toggle pin-7 of the Arduino.
> With the values as in the listing I measure a frequency of 15,2 Hz with my scoop.
> 
> When I change some of the preload value by hand no change is seeing.
> Frequency is staying at 15,2 Hz.
> 
> When I print the value of TCNT1 after setting, and compare this one after
> timer1.start there is a difference
> 
> First value = 63536 and the Second value = 31033.
> 
> I think some where in amForth TCNT1 is overwritten!
> 
> Please can you take a look.
> 
> I included my program.
> 
> Cheers,
> 
> Jan
> 
> \ TIMER1_interrupt
> 
> marker --timer1_interrupt--
> 
> PORTD 7 portpin: PD7
> PD7 pin_output
> 
> &26 constant TIMER1_OVFAddr
> 
> : togglePD7
>    PD7 pin_high? if PD7 low else PD7 high then
> ;
> 
> : timer1.isr
>   \ toggle output PD7
>   togglePD7
> ;
> 
> \ preload for overflow interrupt every 1 ms
> \ preload = 65536 - (f_cpu / (prescaler * 1000))
> 
> : timer1.preload
>    f_cpu #1000 um/mod nip 8 / negate  \ <===== if i change the value #1000 notting is change
> ;
> 
> : timer1.init ( -- )
>     timer1.preload TCNT1 !
>     TCNT1 @ u. cr   \ <===============  print value of TCNT1 ===========
>     ['] timer1.isr TIMER1_OVFAddr int!
> ;
> 
> : timer1.start
>     -int
>     timer1.init
>     %00000010 TCCR1B c! \ prescaler 8
>     %00000001 TIMSK1 c! \ enable overflow interrupt
>     +int
> ;
> 
> : timer1.stop
>    %00000000 TCCR1B c! \ stop timer
>    %00000000 TIMSK1 c! \ stop interrupt
> ;
> 
> 
> 
> _______________________________________________
> Amforth-devel mailing list for http://amforth.sf.net/
> Amf...@li...
> https://lists.sourceforge.net/lists/listinfo/amforth-devel
> 

Re: [Amforth] Question about Timer1 - is there a bug?

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

> I think some where in amForth TCNT1 is overwritten!

I can assure you, that there is no code in plain amforth
that overwrites your settings. It's either your code or
the hardware itself.

Matthias

Re: [Amforth] Question about Timer1 - is there a bug?

[Richard B. <ric...@gm...>]

Hi Jan

I suggest that the ISR has to toggle the pin and re-load the timer1 counter.

>From memory timer1 counts upwards and once it overflows it just keeps
counting up from zero unless you re-load it.

Regards
Richard

On 11/3/18, Jan Kromhout <kro...@ho...> wrote:
> Hi,
>
> I have taken the TIMER_1 example, and make some small change.
> Instead of the timer1.tick I toggle pin-7 of the Arduino.
> With the values as in the listing I measure a frequency of 15,2 Hz with my
> scoop.
>
> When I change some of the preload value by hand no change is seeing.
> Frequency is staying at 15,2 Hz.
>
> When I print the value of TCNT1 after setting, and compare this one after
> timer1.start there is a difference
>
> First value = 63536 and the Second value = 31033.
>
> I think some where in amForth TCNT1 is overwritten!
>
> Please can you take a look.
>
> I included my program.
>
> Cheers,
>
> Jan
>
> \ TIMER1_interrupt
>
> marker --timer1_interrupt--
>
> PORTD 7 portpin: PD7
> PD7 pin_output
>
> &26 constant TIMER1_OVFAddr
>
> : togglePD7
>    PD7 pin_high? if PD7 low else PD7 high then
> ;
>
> : timer1.isr
>   \ toggle output PD7
>   togglePD7
> ;
>
> \ preload for overflow interrupt every 1 ms
> \ preload = 65536 - (f_cpu / (prescaler * 1000))
>
> : timer1.preload
>    f_cpu #1000 um/mod nip 8 / negate  \ <===== if i change the value #1000
> notting is change
> ;
>
> : timer1.init ( -- )
>     timer1.preload TCNT1 !
>     TCNT1 @ u. cr   \ <===============  print value of TCNT1 ===========
>     ['] timer1.isr TIMER1_OVFAddr int!
> ;
>
> : timer1.start
>     -int
>     timer1.init
>     %00000010 TCCR1B c! \ prescaler 8
>     %00000001 TIMSK1 c! \ enable overflow interrupt
>     +int
> ;
>
> : timer1.stop
>    %00000000 TCCR1B c! \ stop timer
>    %00000000 TIMSK1 c! \ stop interrupt
> ;
>
>
>
> _______________________________________________
> Amforth-devel mailing list for http://amforth.sf.net/
> Amf...@li...
> https://lists.sourceforge.net/lists/listinfo/amforth-devel
>

Re: [Amforth] Question about Timer1 - is there a bug?

[Jan K. <kro...@ho...>]

Hi,

Thanks all for the suggestions. After reload the timer after every interrupt it is working great.

My leaving question is the word   “f_cpu” in the code of Timer1.frt. When I execute it I get two values on the stack.

What is the meaning of this two values?

Cheers,

Jan





Op 3 nov. 2018, om 12:31 heeft Richard Burden <ric...@gm...<mailto:ric...@gm...>> het volgende geschreven:

Hi Jan

I suggest that the ISR has to toggle the pin and re-load the timer1 counter.

From memory timer1 counts upwards and once it overflows it just keeps
counting up from zero unless you re-load it.

Regards
Richard

On 11/3/18, Jan Kromhout <kro...@ho...<mailto:kro...@ho...>> wrote:
Hi,

I have taken the TIMER_1 example, and make some small change.
Instead of the timer1.tick I toggle pin-7 of the Arduino.
With the values as in the listing I measure a frequency of 15,2 Hz with my
scoop.

When I change some of the preload value by hand no change is seeing.
Frequency is staying at 15,2 Hz.

When I print the value of TCNT1 after setting, and compare this one after
timer1.start there is a difference

First value = 63536 and the Second value = 31033.

I think some where in amForth TCNT1 is overwritten!

Please can you take a look.

I included my program.

Cheers,

Jan

\ TIMER1_interrupt

marker --timer1_interrupt--

PORTD 7 portpin: PD7
PD7 pin_output

&26 constant TIMER1_OVFAddr

: togglePD7
  PD7 pin_high? if PD7 low else PD7 high then
;

: timer1.isr
 \ toggle output PD7
 togglePD7
;

\ preload for overflow interrupt every 1 ms
\ preload = 65536 - (f_cpu / (prescaler * 1000))

: timer1.preload
  f_cpu #1000 um/mod nip 8 / negate  \ <===== if i change the value #1000
notting is change
;

: timer1.init ( -- )
   timer1.preload TCNT1 !
   TCNT1 @ u. cr   \ <===============  print value of TCNT1 ===========
   ['] timer1.isr TIMER1_OVFAddr int!
;

: timer1.start
   -int
   timer1.init
   %00000010 TCCR1B c! \ prescaler 8
   %00000001 TIMSK1 c! \ enable overflow interrupt
   +int
;

: timer1.stop
  %00000000 TCCR1B c! \ stop timer
  %00000000 TIMSK1 c! \ stop interrupt
;



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Amforth-devel mailing list for http://amforth.sf.net/
Amf...@li...<mailto:Amf...@li...>
https://lists.sourceforge.net/lists/listinfo/amforth-devel



_______________________________________________
Amforth-devel mailing list for http://amforth.sf.net/
Amf...@li...<mailto:Amf...@li...>
https://lists.sourceforge.net/lists/listinfo/amforth-devel

Re: [Amforth] Question about Timer1 - is there a bug?

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

> My leaving question is the word   “f_cpu” in the code of Timer1.frt.
> When I execute it I get two values on the stack.

It's the current clock the controller is running at.
It's a double cell number, since the 16bit controllers
run too fast to keep this number in a single cell.

Matthias