Datasheet

 2006-2012 Microchip Technology Inc. DS41291G-page 107
PIC16F882/883/884/886/887
9.2.6 A/D CONVERSION PROCEDURE
This is an example procedure for using the ADC to
perform an Analog-to-Digital conversion:
1. Configure Port:
• Disable pin output driver (See TRIS register)
• Configure pin as analog
2. Configure the ADC module:
• Select ADC conversion clock
• Configure voltage reference
• Select ADC input channel
• Select result format
• Turn on ADC module
3. Configure ADC interrupt (optional):
• Clear ADC interrupt flag
• Enable ADC interrupt
• Enable peripheral interrupt
• Enable global interrupt
(1)
4. Wait the required acquisition time
(2)
.
5. Start conversion by setting the GO/DONE bit.
6. Wait for ADC conversion to complete by one of
the following:
• Polling the GO/DONE
bit
• Waiting for the ADC interrupt (interrupts
enabled)
7. Read ADC Result
8. Clear the ADC interrupt flag (required if interrupt
is enabled).
EXAMPLE 9-1: A/D CONVERSION
Note 1: The global interrupt can be disabled if the
user is attempting to wake-up from Sleep
and resume in-line code execution.
2: See Section 9.3 “A/D Acquisition
Requirements”.
;This code block configures the ADC
;for polling, Vdd and Vss as reference, Frc
clock and AN0 input.
;
;Conversion start & polling for completion
; are included.
;
BANKSEL ADCON1 ;
MOVLW B’10000000’ ;right justify
MOVWF ADCON1 ;Vdd and Vss as Vref
BANKSEL TRISA ;
BSF TRISA,0 ;Set RA0 to input
BANKSEL ANSEL ;
BSF ANSEL,0 ;Set RA0 to analog
BANKSEL ADCON0 ;
MOVLW B’11000001’ ;ADC Frc clock,
MOVWF ADCON0 ;AN0, On
CALL SampleTime ;Acquisiton delay
BSF ADCON0,GO ;Start conversion
BTFSC ADCON0,GO ;Is conversion done?
GOTO $-1 ;No, test again
BANKSEL ADRESH ;
MOVF ADRESH,W ;Read upper 2 bits
MOVWF RESULTHI ;store in GPR space
BANKSEL ADRESL ;
MOVF ADRESL,W ;Read lower 8 bits
MOVWF RESULTLO ;Store in GPR space