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Rob_975
Joined: 14 Aug 2012
Posts: 16
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| PIC18F452 @ 20MHz slowdown by LED. |
 Posted: Tue Oct 30, 2012 2:34 pm |
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Hi,
I have a PIC18F452 with 20MHz crystal behaving strange.
When I insert the lines :
| Code: |
output_low(PIN_D7);
delay_ms(1500);
output_high(PIN_D7);
delay_ms(100); |
The PIC seems to be slow and the text on the LCD display is changing slowly (like when a LCD is working at low temperature). The LED is blinking OK.
When those lines are greyed out, everything is fine, and the display is reactive.
Compiler 4.120
Cheers. |
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Mike Walne
Joined: 19 Feb 2004
Posts: 1785
Location: Boston Spa UK
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| Posted: Tue Oct 30, 2012 2:40 pm |
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You're adding a 1.6 second delay into your system.
Why are you surprised that everything seems to be so tardy?
Mike |
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temtronic
Joined: 01 Jul 2010
Posts: 9162
Location: Greensville,Ontario
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| Posted: Tue Oct 30, 2012 2:42 pm |
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Every delay_ms(xxx),delay_us(xxx),etc. the PIC will 'twiddle it's thumbs' and do NOTHING except loop around and around, counting down until the total time expires for the 'delay'.
NOTHING else can happen until the PIC exits the delay routine...
If you printout the listing and read the delay_aa(xxx) code, you'll see why.
If you want the PIC to do anything else while a 'delay' is in progress, you need to run timers and interrupts to achieve 'multitasking'.
hth
jay |
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