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derricko
Joined: 03 Sep 2010
Posts: 8
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| Create do re mi with 16f887 using 8Mhz crystal |
 Posted: Mon Nov 22, 2010 4:21 am |
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| Code: |
const int s_table[] = {128,176,218,246,255,246,218,176,
128,79,37,9,0,9,37,79};
static int t0preload,frequency=150;
#int_timer2
void pwm_load(void) {
setup_ccp1(CCP_PWM);
set_pwm1_duty(s_table[s_tableidx++ % 8]);
set_timer2(t0preload);
}
main()
{
setup_ccp1(CCP_PWM);
t0preload = 100;//256 - (62500 / frequency);
setup_timer_2(T2_DIV_BY_4,frequency,1);
blah blah....
}
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I try to create a code as modified from
http://www.ccsinfo.com/forum/viewtopic.php?t=36540
I try to work out a code to generate a good Do Re Mi Tone for my project.
It doesn't seem to work well, the tone generated is generally some kind of noise with 2 tones. I have no idea what I have done wrong. Guess my knowledge on timer with PWM is very limited. Quite confused with the frequency component as stated in the thread.... Anybody can help? Appreciated.  |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Wed Nov 24, 2010 3:29 pm |
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Try modifying the CCS example file, Ex_Tones.c and the driver file for it, tones.c.
I did this. I edited the Ex_tones.c file and removed the data for their
"Happy Birthday" music. I added the DoReMi notes. It works.
These are the changes I made above main():
| Code: | #define SIZE 8
const struct
{
long tone;
long length;
}doremi[] = {
C_note[0], 400
D_note[0], 400,
E_note[0], 400,
F_note[0], 400,
G_note[0], 400,
A_note[0], 400,
B_note[0], 400,
C_note[1], 800 // Use next higher octave for last note
}; |
In main(), I edited the code in the for() loop to use the 'doremi' data:
| Code: |
generate_tone(doremi[i].tone, doremi[i].length); |
In the Tones.c file, I changed the output pin to be Pin C2, because my
PicDem2-Plus board has a beeper on pin C2:
| Code: | | #define TONE_PIN PIN_C2 |
To make it work with an 8 MHz crystal, edit the #use delay() statement
so it has 8 MHz in it:
| Code: | #include <16F877.h>
#fuses HS,NOWDT,NOPROTECT,NOLVP
#use delay(clock=8000000) |
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derricko
Joined: 03 Sep 2010
Posts: 8
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| Posted: Sun Nov 28, 2010 7:33 pm |
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Thank you PCM, I will give a try  |
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gpsmikey
Joined: 16 Nov 2010
Posts: 588
Location: Kirkland, WA
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| Posted: Sun Jan 16, 2011 1:31 pm |
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| Quote: |
In the Tones.c file, I changed the output pin to be Pin C2, because my
PicDem2-Plus board has a beeper on pin C2: |
In looking at the PicDem2-Plus board schematics, I see they are creating sort of a fake "H drive" to the Piezo buzzer" but with their configuration, there is always a DC voltage applied to the piezo element. In reading the spec sheets for a number of them, it indicates you should not have a DC bias on the piezo element. Has this been a problem for those with the PicDem board or does it seem to work just fine ?
mikey
_________________
mikey
-- you can't have too many gadgets or too much disk space !
old engineering saying: 1+1 = 3 for sufficiently large values of 1 or small values of 3 |
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