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haxan7
Joined: 27 Jul 2013
Posts: 79
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| #USE TIMER, can't generate 1s ticks |
 Posted: Tue Aug 13, 2013 2:05 pm |
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Compiler Version 4.140.
Frequency of osc = 16Mhz
| Code: | | #USE TIMER(TIMER=1,TICK=500ms,BITS=16,NOISR) |
Timebase wrong for this timer
| Code: | | #USE TIMER(TIMER=1,TICK=700ms,BITS=16,NOISR) |
Timer 1 tick time is 8.19 ms.
| Code: | | #USE TIMER(TIMER=1,TICK=1024ms,BITS=16,NOISR) |
Timer 1 tick time is 65.54 ms.
| Code: | | #USE TIMER(TIMER=1,TICK=1s,BITS=16,NOISR) |
Timer 1 tick time is 16.38 ms.
It is completely haywire...
How do i generate ticks for 1s? |
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alan
Joined: 12 Nov 2012
Posts: 357
Location: South Africa
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| Posted: Tue Aug 13, 2013 2:21 pm |
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Have you defined your
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#use delay(frequency);
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Ttelmah
Joined: 11 Mar 2010
Posts: 19568
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| Posted: Tue Aug 13, 2013 2:21 pm |
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You can't.....
One key thing with setting like this, is _you_ need to work within the limits of the chip.
Timer1 Max prescaler=/8
16bit = /65536
Chip internally feeds prescaler with FOSC/4.
So maximum division = /(4*65536*8) = /2097152
So just under 8 ticks per second.
Much better and safer to setup the timer yourself, and check the numbers you use....
The ticks function can do this automatically, but you need to allow a larger counter (32bit), and unless you are calling the get_ticks function quite frequently, you should use the ISR option.
You really want to let the tick run much faster (1mSec), and then 1 sec has passed when 'get_ticks' increments by 1000.
Best Wishes |
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temtronic
Joined: 01 Jul 2010
Posts: 9255
Location: Greensville,Ontario
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| Posted: Tue Aug 13, 2013 2:32 pm |
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Have a look in the 'code library' forum here...
There's a software RTC program that should help you.
hth
jay |
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haxan7
Joined: 27 Jul 2013
Posts: 79
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| Posted: Wed Aug 14, 2013 2:12 am |
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| Ttelmah wrote: | You can't.....
One key thing with setting like this, is _you_ need to work within the limits of the chip.
Timer1 Max prescaler=/8
16bit = /65536
Chip internally feeds prescaler with FOSC/4.
So maximum division = /(4*65536*8) = /2097152
So just under 8 ticks per second.
Much better and safer to setup the timer yourself, and check the numbers you use....
The ticks function can do this automatically, but you need to allow a larger counter (32bit), and unless you are calling the get_ticks function quite frequently, you should use the ISR option.
You really want to let the tick run much faster (1mSec), and then 1 sec has passed when 'get_ticks' increments by 1000.
Best Wishes |
I thought every things was managed by the compiler. I will try and write a timer myself |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19568
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| Posted: Wed Aug 14, 2013 2:24 am |
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Yes, it is, but within the limitations of the hardware.
'Ticks' don't do anything. They are just a count.
It doesn't generate interrupts at the tick interval, or do anything at the tick interval, except 'count'. It has though, to have some way of counting 'at' the specified interval. 1second is just too slow for any tick to happen (at your crystal frequency, with the specified counter size).
The code Temtronic refers you to, is a _very efficient_ (more than any generic version the compiler can generate) way to handle doing accurate times with a hardware tick at an interval that is not an exact sub multiple of the 'time' required.
Or as I said before, use a 'tick' at something like a mSec, and then do the job you want when this reaches 1000.
Best Wishes |
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