7.96Hz Sinewave Generator Using A Pic Chip - Joe's Cat Website


This small project was a quick solution for someone that had an interest in generating a slow sinewave with a frequency of 7.96Hz similar in frequency with the Earth's magnetism and resonances.


HOW THIS WORKS

Basically, this circuit runs on a crystal at 4MHz for timing, and from this speed, the program produces a 0 to 255 sinewave value which is output to a Digital-to-Analog resistor ladder on PORTB that can be used by another circuit.


GET THE FILE

You can download Sinewave Generator, or you can copy and paste the code shown below into your ASM code editor.

	title  '7.96 Hertz Sinewave Program, Copyright Jose Da Silva, Nov95'
	list   p=16C54,f=INHX8M,C=120,T=on,ST=off
	#include "P16C5X.INC"
	__fuses  _CP_OFF&_WDT_ON&_XT_OSC
	__idlocs h'9511'	;year/month

	org	08h		;scratch variables
acca	equ	.8		;res	1
accb	equ	.9		;res	1
accc	equ	.10		;res	1

;best times for a 4MHz xtal: 243(wavetable)*517(wait increment)=7.9598Hz+%error

	org	0
;******************************************************************************
;Wave table values for PORTB Digital-to-Analog resistor ladder, from 0..255..0
;enter	:w=table.position
;exit	:w=value
;time	:4cycles
wav_tbl addwf	PCL,f		;get next sinewave increment
	dt	000,000,000,000,001,001,002,002,003,004,004,005,006,007,008,009
	dt	00B,00C,00E,00F,011,012,014,016,018,01A,01C,01E,020,022,024,027
	dt	029,02C,02E,031,033,036,039,03C,03E,041,044,047,04A,04D,050,053
	dt	056,059,05D,060,063,066,069,06D,070,073,076,07A,07D,080,084,087
	dt	08A,08D,091,094,097,09A,09E,0A1,0A4,0A7,0AA,0AD,0B0,0B4,0B7,0B9
	dt	0BC,0BF,0C2,0C5,0C8,0CA,0CD,0D0,0D2,0D5,0D7,0D9,0DC,0DE,0E0,0E2
	dt	0E4,0E6,0E8,0EA,0EC,0EE,0EF,0F1,0F2,0F4,0F5,0F6,0F7,0F8,0F9,0FA
	dt	0FB,0FC,0FD,0FD,0FE,0FE,0FE,0FF,0FF,0FF,0FF,0FF,0FE,0FE,0FE,0FE
	dt	0FD,0FD,0FC,0FB,0FA,0F9,0F8,0F7,0F6,0F5,0F4,0F2,0F1,0EF,0EE,0EC
	dt	0EA,0E8,0E6,0E4,0E2,0E0,0DE,0DC,0D9,0D7,0D5,0D2,0D0,0CD,0CA,0C8
	dt	0C5,0C2,0BF,0BC,0B9,0B7,0B4,0B0,0AD,0AA,0A7,0A4,0A1,09E,09A,097
	dt	094,091,08D,08A,087,084,080,07D,07A,076,073,070,06D,069,066,063
	dt	060,05D,059,056,053,050,04D,04A,047,044,041,03E,03C,039,036,033
	dt	031,02E,02C,029,027,024,022,020,01E,01C,01A,018,016,014,012,011
	dt	00F,00E,00C,00B,009,008,007,006,005,004,003,003,002,002,001,001
	dt	000,000,000
wav_len equ	$-wav_tbl-1

	org	0FFh
;******************************************************************************
;main pause for 4Mhz xtal
;enter	:
;exit	:w=0, f=:acca=0,accb=0
;time	:(proper time delay)=517-13-4
m_pause movlw	0A4+1		;init pause delay
	movwf	acca
m_pausl decfsz	acca,f		;wait a moment
	goto	m_pausl
	clrwdt			;(make sure watch dog still okay)
	nop			;(time adjustment)
	retlw	0
;******************************************************************************
main	clrwdt			;initialize watch dog timer
	movlw	b'00001111'	;set options register
	option
	movlw	0		;init ports as outputs only (no loose inputs)
	movwf	PORTA
	movwf	PORTB
	tris	PORTA
	tris	PORTB
#ifdef __16C55
	movwf	PORTC
	tris	PORTC
#endif
#ifdef __16C57
	movwf	PORTC
	tris	PORTC
#endif
	clrf	acca		;init scratch variables
	clrf	accb
;do the 'wave'
mainLp	call	m_pause		;wait a bit
	incf	accb,f		;update wave table pointer
	movlw	wav_len		;(reset to zero if end of table)
	subwf	accb,w
	skpnz
	movwf	accb
	movf	accb,w		;get next sinewave increment
	call	wav_tbl
	movwf	PORTB		;output sinewave increment
	goto	mainLp
;******************************************************************************
#ifdef __16C54
	org	1FFh
#endif
#ifdef __16C55
	org	1FFh
#endif
#ifdef __16C57
	org	3FFh
#endif
#ifdef __16C58
	org	3FFh
#endif
start	goto	main		;program starts here on reset
	end

If you find this program useful for yourself, or a project, I will appreciate a little credit for providing it here for your use/project (for example, in your source code comments, or even a web link back to this web page is great if you have a project that uses it that you want to show/demonstrate).

Thanks.

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