PIC16F882_09 Datasheet, PDF (105/328 Pages) Microchip Technology – 28/40/44-Pin, Enhanced Flash-Based 8-Bit CMOS Microcontrollers with nanoWatt Technology

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).
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”.
EXAMPLE 9-1: A/D CONVERSION
;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
© 2009 Microchip Technology Inc.
DS41291F-page 103