;************************************************************************ ; * ; Filename: BA_L10-ADC_Vdd-measure.asm * ; Date: 25/1/10 * ; File Version: 1.2 * ; * ; Author: David Meiklejohn * ; Company: Gooligum Electronics * ; * ;************************************************************************ ; * ; Architecture: Baseline PIC * ; Processor: 16F506 * ; * ;************************************************************************ ; * ; Files required: none * ; * ;************************************************************************ ; * ; Description: Lesson 10, example 3 * ; * ; Demonstrates use of 0.6V ref with ADC to test supply voltage * ; * ; Continuously samples 0.6V internal reference, * ; displaying result as 2 x hex digits on multiplexed 7-seg displays * ; Turns on warning LED if measurement > threshold * ; * ;************************************************************************ ; * ; Pin assignments: * ; AN0 = voltage to be measured (e.g. pot or LDR) * ; RB5, RC0-5 = 7-segment display bus (common cathode) * ; RB4 = tens enable (active high) * ; RB1 = ones enable * ; RB2 = warning LED * ; * ;************************************************************************ list p=16F506 #include radix dec ;***** CONFIGURATION ; ext reset, no code protect, no watchdog, 4MHz int clock __CONFIG _MCLRE_ON & _CP_OFF & _WDT_OFF & _IOSCFS_OFF & _IntRC_OSC_RB4EN ; pin assignments #define TENS PORTB,4 ; tens enable #define ONES PORTB,1 ; ones enable #define WARN PORTB,2 ; warning LED ;***** CONSTANTS constant MINVDD=3500 ; Minimum Vdd (in mV) constant VRMAX=255*600/MINVDD ; Threshold for 0.6 V ref measurement ;***** VARIABLE DEFINITIONS UDATA_SHR digit res 1 ; digit to be displayed ;***** RESET VECTOR ***************************************************** RESET CODE 0x000 ; effective reset vector movwf OSCCAL ; update OSCCAL with factory cal value pagesel start goto start ; jump to main program ;***** Subroutine vectors set7seg ; display digit on 7-segment display pagesel set7seg_R goto set7seg_R ;***** MAIN PROGRAM ***************************************************** MAIN CODE ;***** Initialisation start ; configure ports clrw ; configure PORTB and PORTC as all outputs tris PORTB tris PORTC clrf CM1CON0 ; disable Comparator 1 (RB0, RB1, RB2 usable) clrf CM2CON0 ; disable Comparator 2 (RC0, RC1, RC4 usable) clrf VRCON ; disable CVref (RC2 usable) ; configure ADC movlw b'00111101' ; 00------ no analog inputs (ANS = 00) -> RB0-2 usable ; --11---- clock = INTOSC/4 (ADCS = 11) ; ----11-- select 0.6 V reference (CHS = 11) ; -------1 turn ADC on (ADON = 1) movwf ADCON0 ; configure timer movlw b'11010111' ; configure Timer0: ; --0----- timer mode (T0CS = 0) -> RC5 usable ; ----0--- prescaler assigned to Timer0 (PSA = 0) ; -----111 prescale = 256 (PS = 111) option ; -> increment every 256 us ; (TMR0<2> cycles every 2.048ms) ;***** Main loop main_loop ; sample 0.6 V reference bsf ADCON0,GO ; start conversion w_adc btfsc ADCON0,NOT_DONE ; wait until conversion complete goto w_adc ; test for low Vdd (measured 0.6 V > threshold) movlw VRMAX subwf ADRES,w ; if ADRES > VRMAX btfsc STATUS,C bsf WARN ; turn on warning LED ; display high nybble for 2.048 ms w10_hi btfss TMR0,2 ; wait for TMR0<2> to go high goto w10_hi swapf ADRES,w ; get "tens" digit andlw 0x0F ; from high nybble of ADC result pagesel set7seg call set7seg ; then output it pagesel $ bsf TENS ; enable "tens" display w10_lo btfsc TMR0,2 ; wait for TMR<2> to go low goto w10_lo ; display ones for 2.048 ms w1_hi btfss TMR0,2 ; wait for TMR0<2> to go high goto w1_hi movf ADRES,w ; get ones digit andlw 0x0F ; from low nybble of ADC result pagesel set7seg call set7seg ; then output it pagesel $ bsf ONES ; enable ones display w1_lo btfsc TMR0,2 ; wait for TMR<2> to go low goto w1_lo ; repeat forever goto main_loop ;***** LOOKUP TABLES **************************************************** TABLES CODE 0x200 ; locate at beginning of a page ; Lookup pattern for 7 segment display on port B ; RB5 = G get7sB addwf PCL,f retlw b'000000' ; 0 retlw b'000000' ; 1 retlw b'100000' ; 2 retlw b'100000' ; 3 retlw b'100000' ; 4 retlw b'100000' ; 5 retlw b'100000' ; 6 retlw b'000000' ; 7 retlw b'100000' ; 8 retlw b'100000' ; 9 retlw b'100000' ; A retlw b'100000' ; b retlw b'000000' ; C retlw b'100000' ; d retlw b'100000' ; E retlw b'100000' ; F ; Lookup pattern for 7 segment display on port C ; RC5:0 = ABCDEF get7sC addwf PCL,f retlw b'111111' ; 0 retlw b'011000' ; 1 retlw b'110110' ; 2 retlw b'111100' ; 3 retlw b'011001' ; 4 retlw b'101101' ; 5 retlw b'101111' ; 6 retlw b'111000' ; 7 retlw b'111111' ; 8 retlw b'111101' ; 9 retlw b'111011' ; A retlw b'001111' ; b retlw b'100111' ; C retlw b'011110' ; d retlw b'100111' ; E retlw b'100011' ; F ; Display digit passed in W on 7-segment display set7seg_R movwf digit ; save digit call get7sB ; lookup pattern for port B movwf PORTB ; then output it movf digit,w ; get digit call get7sC ; then repeat for port C movwf PORTC retlw 0 END