Jeffrey,

At this point in a project I usually decide I have bit off more than I can
chew.  If I were approaching this problem, I'd start with very simple code,
produce a square wave.  You'll probably find there is some really simple bug
that even shows up here.


As far as CCS goes, it automatically puts a SLEEP command at the end of your
code, for no apparent reason.  Most of my CCS programs run inside an
infinite loop:

DO{

... some code...

}While (TRUE);

otherwise the program steps off into the SLEEP command or wanders into
unitiialized code space.

I'll dig out some code I was working on in this vein and post it.


-- Lawrence Lile




----- Original Message -----
From: "Jeffrey Frey" <jeff@TENGAM.COM>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Wednesday, September 27, 2000 9:55 AM
Subject: [PIC]: Sine wave with CCS and 16C774


> Hello everyone, please excuse my ignorance on this topic but I have really
> been trying to figure this out and I'm in need of assistance.  I am trying
> to produce a sine wave output with a 16C774.  I am using CCS's compiler
and
> they have sine function implemented but I feel that I don't need the
> accuracy (floating point) that it provides nor the memory it uses.  I have
> looked at some assembly code that Eric Smith developed using a Sine table
> and I think that it will be the most efficient.  What I will be doing is
> writing the result to an 8-bit D/A converter and sweeping through each of
> the 256 steps.  I think that this resolution is more than enough for my
> application.
>
> Here is my problem, I'm very new to the PIC and especially the compiler.
I
> tried entering the code found here
> http://www.brouhaha.com/~eric/pic/sine.html and I can't figure out for the
> life of me how to get it to compile.  On this webpage it is not really
clear
> on the input and the output either.  Can someone point me in the right
> direction so that I can get my code to compile?
>
> Also, as an aside.  In CCS I was having problems at the end of my main
> function because it put the PIC into sleep mode.  I put an empty do-while
> loop at the end to allow the Interrupts to continue to run.  Is this the
> right way to end in my situation or is there a better way?
>
> Thanks,
> Jeff Frey
>
> Please also RTP so that I don't overlook any replies in the PICList.
>
> Here is my code:
>
> #include "o:\projects\safari\Safari.h"
>
> /// The following are manually added definitions
> #byte PORTB = 6
> #define ALL_OUT 0
> #define ALL_IN  0xff
>
> int angle;
>
> #int_rtcc
> rtcc_isr() {
>
> #asm
>
> sinetbl:
>         addwf   pc
>         retlw    000h,003h,006h,009h,00ch,010h,013h,016h
>         retlw    019h,01ch,01fh,022h,025h,028h,02bh,02eh
>         retlw    031h,033h,036h,039h,03ch,03fh,041h,044h
>         retlw    047h,049h,04ch,04eh,051h,053h,055h,058h
>         retlw    05ah,05ch,05eh,060h,062h,064h,066h,068h
>         retlw    06ah,06bh,06dh,06fh,070h,071h,073h,074h
>         retlw    075h,076h,078h,079h,07ah,07ah,07bh,07ch
>         retlw    07dh,07dh,07eh,07eh,07eh,07fh,07fh,07fh
>         retlw    07fh
> sine:   movwf   temp    ; save arg
>         btfsc   temp,6  ; is arg in the 2nd or 4th quadrant?
>         sublw   0       ; yes, complement it to reduce to 1st or 3rd
>         andlw   07fh    ; reduce to 1st quadrant
>         call    sinetbl ; get magnitude
>         btfsc   temp,7  ; was it 3rd or 4th quadrant?
>         sublw   0       ; yes, complement result
>         return
>
> #endasm
>
> return;
> }
>
> #int_adcc
> adc_isr() {
>
> }
>
> #int_eeprom
> eeprom_isr() {
>
> }
>
> #int_timer1
> timer1_isr() {
>
> }
>
> #int_timer2
> timer2_isr() {
>
> }
>
>
>
> void main() {
>
>    angle = 10;
>    setup_adc_ports(A_ANALOG);
>    setup_adc(ADC_CLOCK_DIV_2);
>    setup_spi(FALSE);
>    setup_psp(PSP_DISABLED);
>    setup_counters(RTCC_INTERNAL,RTCC_DIV_2);
> //   setup_timer_1(T1_INTERNAL|T1_DIV_BY_1);
> //   setup_timer_2(T2_DIV_BY_16,10,1);
>    setup_ccp1(CCP_OFF);
>    setup_ccp2(CCP_OFF);
>    enable_interrupts(INT_RTCC);
> //   enable_interrupts(INT_ADC);
> //   enable_interrupts(INT_EEPROM);
> //   enable_interrupts(INT_TIMER1);
> //   enable_interrupts(INT_TIMER2);
>    enable_interrupts(global);
>
>    set_tris_b(ALL_OUT);    // Set all pins on PORTB as Outputs
>    PORTB = 0;              // Set all pins on PORTB Low
>
>    angle = 0;              // Initialize angle to 0 degrees
>     do {
>
>     } while(TRUE);
>
> }
>
> --
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>

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