please dont rip this site

16F877 A/D IO Sample Programs

...the ground pin next to the port A pins is used internally in a way that is much closer to the A/D converter, and is thus meant to be the analog ground.

JB says:

After trying unsucessfully to get Microchip's example code (among others) to work, I hacked out this modification which seems to do the job, at least for me. If anyone else is having as a much difficulty as I did, this may help get things going. FWIW, the remaining least-significant bits are in ADRESL but this example makes use of the most-significant 8 bits left justified into ADRESH. 
;16f877 a/d test routine
;
;TEST CIRCUIT:
;pin 11 & 32 = 5VDC
;pin 12 & 31 = 0VDC
;pin 1 = 5VDC
;pin 2 = 0 - 5 VDC analog input (center tap on 20k variable resistor)
;pin 13 & 14 = 4MHz crystal with 18pF capacitors to 0VDC
;pin 15,16,17,18,23,24,25,26 PORTC outputs each to 330 ohm resistor
;       in series with LED to 0VDC
;**********************************************************

        __config _LVP_OFF & _XT_OSC & _WDT_OFF & _PWRTE_ON & _CP_OFF & _BODEN_OFF
& _DEBUG_OFF
        list p=16f877

        include "p16f877.inc"

        ; Start at the reset vector
        org     0x000
        goto    Start
        org     0x004
Interrupt
        retfie
Start
        bsf     STATUS,RP0      ;bank 1
        bcf     STATUS,RP1
        movlw   H'00'
        movwf   TRISC           ;portc [7-0] outputs
        clrf    ADCON1          ;left justified, all inputs a/d
        bcf     STATUS,RP0      ;bank 0
        movlw   B'01000001'     ;Fosc/8 [7-6], A/D ch0 [5-3], a/d on [0]
        movwf   ADCON0
Main
        call    ad_portc
        goto    Main


ad_portc
                                ;wait for acquision time (20uS)
                                ;(non-critical for this test)

        bsf     ADCON0,GO       ;Start A/D conversion
Wait
        btfsc   ADCON0,GO       ;Wait for conversion to complete
        goto    Wait

        movf    ADRESH,W        ;Write A/D result to PORTC
        movwf   PORTC           ;LEDs
        return

        end

Mark Willcox modified Tony Nixons program 

;pwm.asm to learn CCP/PWM of 16f873. Last edited 5/23/2000
;Originated by Tony Nixon and modified by Mark Willcox.
;Grahm
;   This code will light a LED on portC pin RC2/CCP1 and 
;display the 8 bit hex value on portB LEDs or bargraph. The CCP1 LED
;will glow from bright to dim as the pot varies the pulse width. 
;Connect an O-scope to CCP1 and watch the PW vary. This code can be 
;used on other PICs but you will have to change the code to fit it's 
;instruction set. One wire on pot goes to +Vdd and the other end 
;of the pot goes to -Vss/ground. The wiper goes to RA0 input pin.
;You can use any input signal source as long as you don't exceed the 
;chips max specs. For example, a slow sine or ramp wave(1-5Hz) will 
;flash the CCP1 LED. Make sure you use a common ground for the 
;signal generator and PIC board.


        #include <p16F873.inc>
        LIST p=16F873
	errorlevel 1,-302	;to disable MPLAB bank warnings.
        __config _XT_OSC & _PWRTE_ON & _WDT_OFF & _LVE_OFF
		;Some versions of MPLAB use _LVP_OFF
		;This sets all portB pins to output.
;/*---------Declare Registers
STATUS	EQU	03
ADCON	EQU	08
PORTB	EQU	06
F       EQU     1
W       EQU     0
;/*---------Set up chip parameters
	CLRF	CCP1CON	;CCP MODULE IS OFF
	CLRF	TMR2	;CLEAR TIMER2
	MOVLW	0X7F	;
	MOVWF	PR2
	CALL	A2D
	CLRF	INTCON		;DISABLE INTRPTS ANDCLEAR T0IF
	BSF	STATUS,RP0
	BCF	TRISC,2		;MAKE PIN 2 PWM OUTPUT
	CLRF	PIE1		;DISABLE PERIPHERAL INTS
	BCF	STATUS,RP0
	CLRF	PIR1		;CLR PER INT FLAGS
	MOVLW	0X2C		;PWM  MODE, 2LSBs OF DUTY CYCLE=10
	MOVWF	CCP1CON
	BSF	T2CON,TMR2ON	;TIME2 STRTS TO INCREMENT
	;
	 ;CCP1 INT IS DISABLED
	 ;DO POLLING ON THE TMR2 INT FLAG BIT
	;
PWM_PERIOD_MATCH
	BTFSS	PIR1,TMR2IF
	GOTO	PWM_PERIOD_MATCH
	;
	 ;UPDATE THIS PWM PERIOD AND THE FOLLOWING PWM DUTY CYCLE
	;
	BCF	PIR1,TMR2IF
A2D     bsf     STATUS,RP0
        MOVLW   B'00000001'
        MOVWF   TRISA           ;All outputs except RA0.
        CLRF    TRISB		;RA0 is wiper of 50k pot/Vin
        CLRF    TRISC		;PortB is 8 LED output to show 
        MOVLW   B'00001110'     ;Hex value of Vin from pot.
        MOVWF   ADCON1		;left justified, RA0 = input
;/*-----Set up A2D parameters
        MOVLW   B'11010111'     ;prescaler 1:256 tmr0, internal clock
        MOVWF   OPTION_REG
        BCF     STATUS,RP0
        MOVLW   B'01000001'     ;a2d = on, ch0, fosc/8
        MOVWF   ADCON0
;/*-----Delay loop to settle A2D, similar to de-bounce???
mnloop  btfss   INTCON,T0IF     ;50us loop delay @ 4Mhz
        goto    mnloop
;/*-----Stop timer0 interrupt
        BCF     INTCON,T0IF
        BSF     ADCON0,GO_DONE  ;start a2d conversion
WAITA2D NOP                     ;wait 4 finish
        BTFSC   ADCON0,GO_DONE
        GOTO    WAITA2D
;/*-----Put A2D/PWM value in W and send to ports.
        MOVF    ADRESH,W        ;upper 8 bits-ignor lower 3
        MOVWF	CCPR1L		;PWM is output on pin 13 of 16F873
        MOVWF   PORTB		;output Hex value to LEDs
        RETURN			;DUTY CYCLE IS 25% OF PWM PERIOD
        
   END

See:

Questions:

Comments:

file: /Techref/microchip/16f877adsamp.htm, 11KB, , updated: 2011/9/12 15:58, local time: 2024/12/25 05:11,
TOP NEW HELP FIND: 
3.129.70.138:LOG IN
 ©2024 These pages are served without commercial sponsorship. (No popup ads, etc...).Bandwidth abuse increases hosting cost forcing sponsorship or shutdown. This server aggressively defends against automated copying for any reason including offline viewing, duplication, etc... Please respect this requirement and DO NOT RIP THIS SITE. Questions?
Please DO link to this page! Digg it! / MAKE!

<A HREF="http://massmind.org/techref/microchip/16f877adsamp.htm"> 16F877A/D sample programs</A>
After you find an appropriate page, you are invited to your to this massmind site! (posts will be visible only to you before review) Just type a nice message (short messages are blocked as spam) in the box and press the Post button. (HTML welcomed, but not the <A tag: Instead, use the link box to link to another page. A tutorial is available Members can login to post directly, become page editors, and be credited for their posts.


Link? Put it here: 
if you want a response, please enter your email address: 
Attn spammers: All posts are reviewed before being made visible to anyone other than the poster.
Did you find what you needed?
 

Welcome to massmind.org!

 

Welcome to massmind.org!

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

  .