Datasheet

PIC16(L)F1938/9
DS40001574C-page 154  2011-2013 Microchip Technology Inc.
15.2.6 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 (Refer to the TRIS
register)
• Configure pin as analog (Refer to the ANSEL
register)
2. Configure the ADC module:
• Select ADC conversion clock
• Configure voltage reference
• Select ADC input channel
• 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 15-1: 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: Refer to Section 15.4 “A/D Acquisition
Requirements”
.
;This code block configures the ADC
;for polling, Vdd and Vss references, Frc
;clock and AN0 input.
;
;Conversion start & polling for completion
; are included.
;
BANKSEL ADCON1 ;
MOVLW B’11110000’ ;Right justify, Frc
;clock
MOVWF ADCON1 ;Vdd and Vss Vref
BANKSEL TRISA ;
BSF TRISA,0 ;Set RA0 to input
BANKSEL ANSEL ;
BSF ANSEL,0 ;Set RA0 to analog
BANKSEL ADCON0 ;
MOVLW B’00000001’ ;Select channel AN0
MOVWF ADCON0 ;Turn ADC On
CALL SampleTime ;Acquisiton delay
BSF ADCON0,ADGO ;Start conversion
BTFSC ADCON0,ADGO ;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