To show just how easy it is to port a program downloaded from the internet into a form that PICbasic can understand (or vice-versa) these two panels show a side by side comparison of some 'traffic lights' software for a PIC16C84
| Code from MPASM | Code from PICbasic |
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; WRITTEN BY Nigel Gardner ; COPYRIGHT Bluebird Electronics ; Web http://www.bluebird-electronics.co.uk ; RESONATOR 4.00 MHz XT ; INSTRUCTION CLOCK 1.00 MHz T= 1uS ; ***** equates ***** tmr0 equ 1 ; timer 0 pcl equ 2 ; program counter optreg equ 81h ; option on page 1 trisa equ 85h ; port direction register page 1 trisb equ 86h ; port direction register page 1 status equ 3 ; status register time equ .156 ; 156 * 32ms = approx 5 seconds porta equ 5 auto equ 0 ; manual auto switch step equ 1 ; sequence step switch portb equ 6 red1 equ 0 ; set a of lights yel1 equ 1 green1 equ 2 red2 equ 3 ; set b of lights yel2 equ 4 green2 equ 5 count equ 0ch ; general purpose counter list p=16c84 org 00 ; reset vector goto init ;************************ subroutines ******************** ; test here to see if manual mode or delay if automatic delay btfsc porta,auto ; test for auto switch on goto dly1 ; automatic mode lp1 btfsc porta,step ; if manual mode, then wait for goto delay ; button press but check if auto btfss porta,step ; and then release before continuing goto $-1 ; to next sequence retlw 0 ; long delay 32ms * value in w register dly1 movlw time ; load timer movwf count ; use this register temporarily del1 clrf tmr0 btfss tmr0,7 ; test tmr0 bit 7 128*256us = 32.768ms goto $-1 decfsz count,f ; decrement, until zero goto del1 retlw 0 ; *********** initalise ports and tmr0 ************* init clrf portb bsf status,5 ; set up page 1 movlw 00h movwf trisb ; port b as outputs movlw 0fh movwf trisa ; port a as inputs movlw b'10000111' ; tmr0 pre-scalar /256 pullup off movwf optreg ; 256us per count internal clock bcf status,5 ; set up page 0 ; ********* program begins here ********************** main bsf portb,red1 bsf portb,green2 movlw time ; delay time call delay bsf portb,yel1 bcf portb,green2 bsf portb,yel2 movlw time ; delay time call delay bcf portb,yel1 bcf portb,red1 bsf portb,green1 bsf portb,red2 movlw time ; delay time call delay bcf portb,green1 bsf portb,yel1 bsf portb,yel2 movlw time ; delay time call delay bcf portb,yel1 bcf portb,yel2 bcf portb,red2 goto main end |
REM WRITTEN BY Nigel Gardner REM COPYRIGHT Bluebird Electronics REM Web http://www.bluebird-electronics.co.uk REM RESONATOR 4.00 MHz XT REM INSTRUCTION CLOCK 1.00 MHz T= 1uS REM ***** equates ***** tmr0 = 1 :REM timer 0 pcl = 2 :REM program counter optreg = &81 :REM option on page 1 trisa = &85 :REM port direction register page 1 trisb = &86 :REM port direction register page 1 status = 3 :REM status register time = 156 :REM 156 * 32ms = approx 5 seconds porta = 5 auto = 0 :REM manual auto switch step = 1 :REM sequence step switch portb = 6 red1 = 0 :REM set a of lights yel1 = 1 green1 = 2 red2 = 3 :REM set b of lights yel2 = 4 green2 = 5 count = &0C :REM general purpose counter W=0 F=1 DIM code% 512 FOR pass = 4 TO 7 STEP 3 P%=00 :REM reset vector O%=code% [OPT pass goto init \************************ subroutines ******************** \ test here to see if manual mode or delay if automatic .delay btfsc porta,auto \ test for auto switch on goto dly1 \ automatic mode .lp1 btfsc porta,step \ if manual mode, then wait for goto delay \ button press but check if auto btfss porta,step \ and then release before continuing goto P%-1 \ to next sequence retlw #0 \ long delay 32ms * value in w register .dly1 movlw #time \ load timer movwf count \ use this register temporarily .del1 clrf tmr0 btfss tmr0,7 \ test tmr0 bit 7 128*256us = 32.768ms goto P%-1 decfsz count,F \ decrement, until zero goto del1 retlw #0 \ *********** initalise ports and tmr0 ************* .init clrf portb bsf status,5 \ set up page 0 movlw #&00 movwf trisb \ port b as outputs movlw #&0F movwf trisa \ port a as inputs movlw #%10000111 \ tmr0 pre-scalar /256 pullup off movwf optreg \ 256us per count internal clock bcf status,5 \ set up page 0 \ ********* program begins here ********************** .main bsf portb,red1 bsf portb,green2 movlw #time \ delay time call delay bsf portb,yel1 bcf portb,green2 bsf portb,yel2 movlw #time \ delay time call delay bcf portb,yel1 bcf portb,red1 bsf portb,green1 bsf portb,red2 movlw #time \ delay time call delay bcf portb,green1 bsf portb,yel1 bsf portb,yel2 movlw #time \ delay time call delay bcf portb,yel1 bcf portb,yel2 bcf portb,red2 goto main ] NEXT |
There is a simple 'get you working' project to try which takes the input voltage on line ADC0 and converts that into a VU bar style LED display.
K2
There is a slightly more complex project that acts as a maximum/minimum temperature display with screen saver and user settable alarm point which could then be used to (for example) open a window or buzz a buzzer. It was called K2 after the mountain, and comes complete with diagrams.
CRCcalc
There is a software only project which calculates the 16 bit CRC of a block of data in the PIC and uses the same polynomial code as the BBC micro's tape filing system. This is a good first project to try with the simulator, PICtracer, since it doesn't require any external stimuli.
Software RS232
There is a skeleton of an RS232 serial comms terminal to build (includes diagram). Using the RTS/CTS flow control mechanism it's maximum baud rate is software definable. For each character it receives it echos back "Rx:<letter><cr><lf>" as a demonstration of its use.
