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Trouble with manual PWM

 
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Gerhard



Joined: 30 Aug 2007
Posts: 144
Location: South Africa

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Trouble with manual PWM
PostPosted: Wed Sep 26, 2007 2:31 pm     Reply with quote
I ran the following code on a LED but the led doesn't start from zero brightness and end at full brightness. I tried everything and I am running out of idees. Can somebody please advice why the Led doesnt start at zero brightness until full brightness.

[/double aan = 0;
double af=10000;
int i;
portb=0;
set_tris_a(all_in);
set_tris_b(all_out);

for (i =0;i<=100000;++i)
{
aan = aan+0.1;
af = af-0.1;
output_low(pin_b0);
delay_us(af);
output_high(pin_b0);
delay_us(aan);

}]
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Wed Sep 26, 2007 2:39 pm     Reply with quote
Quote:
int i;
portb=0;
set_tris_a(all_in);
set_tris_b(all_out);

for (i =0;i<=100000;++i)

For starters, an 'int' in CCS is an unsigned 8-bit number.
It's not ANSI C. It can only hold a value of 0 to 255.

There is a very good chart in the latest CCS manual, which
shows the CCS data types and their range of values.
Download the manual here:
http://www.ccsinfo.com/downloads/CReferenceManual.pdf
The chart is on page 49 in the Acrobat reader.

All integer data types are 'unsigned' by default.
Gerhard



Joined: 30 Aug 2007
Posts: 144
Location: South Africa

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PostPosted: Wed Sep 26, 2007 2:46 pm     Reply with quote
thanks. It seems to work.
Will this be equavalent to a normal PWM output on a port if I just fine tune the frequency?
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