Barcode reader with PIC16f877A ?

[iugmoh]

Thank you for your reply and your information, i will try to change my code now and see if it's working.

[iugmoh]

I modify my code, and it's more stable and better than previous which give me the number of bits were scanned counter=96 but previous it's not the same,
Here is my code after modifications
====================================

DEFINE LCD_DREG PORTD 'LCD data port
DEFINE LCD_DBIT 4 'LCD data starting bit 0 or 4
DEFINE LCD_RSREG PORTD 'LCD register select port
DEFINE LCD_RSBIT 2 'LCD register select bit
DEFINE LCD_EREG PORTD 'LCD enable port
DEFINE LCD_EBIT 3 'LCD enable bit
DEFINE LCD_BITS 4 'LCD bus size 4 or 8
DEFINE LCD_LINES 4 'Number lines on LCD
DEFINE OSC 4 ' We're using a 4 MHz oscillator

symbol clock_barcode=portb.0 ; clock of barcode reader ps/2
symbol data_barcode=portb.1 ; data of barcode reader ps/2
symbol but1=portb.2

ID var bit[250]
char var byte
countstep var byte
counter var byte

Clr CON 1 ' Serial LCD command to clear LCD
LINE1 CON 128 ' Line #1 of serial LCD
LINE2 CON 192 ' Line #2 of serial LCD
LINE3 CON 148 ' Line #3 of serial LCD
LINE4 CON 212 ' Line #4 of serial LCD
Ins CON 254 ' Instruction for LCD command-mode



input clock_barcode
input data_barcode
output portd.1
input but1

OPTION_REG = %00000101 ; falling edge of clock
INTCON = %10010000 ' Enable RB0 interrupt
counter=0

pause 2000 ; time for lcd to turn on
ON INTERRUPT GOTO reg_id
lcdout Ins,clr,INS,Line1,"Please Ins. ID card"
goto main

;;;;;;; interrupt service routine
DISABLE ' Disable interrupts in handler
reg_id:
intcon.1=0 ; reset int
if clock_barcode=0 then ; test falling edge
id[counter]=data_barcode
counter=counter+1
endif

RESUME ' Return to main program
ENABLE ' Enable interrupts after handler
;;;;;;;;;;;;;;;;;


Main:


if but1=0 then
lcdout ins,clr,ins,line1,#counter,ins,line2 : pause 3000
for countstep=0 to counter : lcdout #id[countstep] : pause 2000 : next
counter=0
endif

goto main ' Remain in loop

end


=========================

please if one can tell me if my code is true or not ,which it's collect data from barcode reader ps/2 every falling edge trigger of clock which this will tell the microcontroller interrupt service routine to save the data bit on this edge!

[skimask]

One of the problems you're going to have is the fact that you won't get an interrupt in the middle of a statement.
For instance,
Pause 3000...
The On Interrupt won't trigger for at least 3 seconds.
(However, instead of Pause 3000, you can use:
for x = 1 to 300 : pauseus 10 : next x...at least then the PIC will check for an interrupt every 10 microseconds)

Any LCDOUT command won't let an On Interrupt trigger during the execution of the LCDOUT command, which can take a few milliseconds, an eternity when dealing with fast signals.

In general, all interrupts are checked BEFORE or AFTER every statement (I don't remember which). So, if you're executing a single command, an ON INTERRUPT won't happen in the middle of it.

Either recode your program to keep anything in the main loop from holding up an interrupt or think about researching and switching over to DT's Instant Interrupts.

[iugmoh]

[QUOTE=skimask;49542]One of the problems you're going to have is the fact that you won't get an interrupt in the middle of a statement.
QUOTE]

oky I avoid this problem by placing If statement " If but1=0 " which all commands inside this if statement will not execute untill I press the button placed on portb.2

but I want to ask if there is something wrong in my code

[skimask]

oky I avoid this problem by placing If statement " If but1=0 " which all commands inside this if statement will not execute untill I press the button placed on portb.2

You sure did...missed that one, but it's still a valid point for future reference.

but I want to ask if there is something wrong in my code

Does it work?

If code_works = 1 then
nothing_wrong_with_code = 1
else
nothing_wrong_with_code = 0
something_wrong_with_code = 1
endif

[iugmoh]

You sure did...missed that one, but it's still a valid point for future

oky for testing my code I insert ID card with this number "120063718" and the barcode give me a sound that the scanning completed , then if the scanning stage I pressed the button to display the data collected from this barcode reader the data output as follows

counter=96
data bits=
10100001001111100010000011111100111110001000000111 0100101101011000000111010000011111100 ...........

I want to know how to decode this data to display this ID number 120063718

[skimask]

oky for testing my code I insert ID card with this number "120063718" and the barcode give me a sound that the scanning completed , then if the scanning stage I pressed the button to display the data collected from this barcode reader the data output as follows
counter=96
data bits=
10100001001111100010000011111100111110001000000111 0100101101011000000111010000011111100 ...........
I want to know how to decode this data to display this ID number 120063718

For one thing, we don't know which barcode scanner you're using (not that it would matter much).
Second thing, how does your scanner encode the information that it outputs?
Obviously you've got data there. Whether it's good data or not is another story.
What do the dots mean? Do they mean that there is more data to follow or are those the end of the string?
Is this some sort of ASCII encoded data? BCD? Grey code? Otherwise? 8 bit data chunks? 12 bit? 4 bit repeated/inverted?