Barcode reader with PIC16f877A ?

[iugmoh]

Hi all,
I need your help in attendance registration project : I decide to register my students attendance automatically where each student has ID card with he's own number printed in barcode format with 11 digits like this "120061235" when we scaned it.
I read alot about barcode reader ps/2 protocol and know how it works and how i can interface with PIC16f877a , but i don't where is the problem I don't know how to display this ID number on an LCD for example

I use the interrupt to get clock
please anyone have an idea how to read barcode reader and display on LCD ?

here is my code:
Include "Modedefs.Bas"
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

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


symbol SCL = PORTC.3 ' I2C CLOCK pin
symbol SDA = PORTC.4 ' I2C DATA pin
symbol clock_barcode=portb.0
symbol data_barcode=portb.1
input clock_barcode
input data_barcode
output portd.1
symbol but1=portb.2
input but1
portd.1=0

ON INTERRUPT GOTO reg_id
OPTION_REG = %00000101 ; falling edge of clock
pause 2000
INTCON = %10010000 ' Enable RB0 interrupt

Addr Var byte ' 8-bit memory address in EEPROM
EE_ByteOut Var Byte ' Variable whose value is to be stored to EEPROM
EE_ByteIn Var Byte ' Variable for storing the value read from EEPROM
ID var bit[250]
char var byte
countstep var byte
counter var byte

counter=0
TRISD = 0 ' Port D is output
EE_ByteOut=0

lcdout Ins,clr,INS,Line1,"Please Ins. ID card"
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

DISABLE ' Disable interrupts in handler
reg_id:



if clock_barcode=0 then ; test falling edge
id[counter]=data_barcode

endif

counter=counter+1

portd.1=data_barcode ' Turn on LED when interrupted
intcon.1=0 ; reset int
RESUME ' Return to main program
ENABLE ' Enable interrupts after handler

[skimask]

I read alot about barcode reader ps/2 protocol and know how it works and how i can interface with PIC16f877a , but i don't where is the problem I don't know how to display this ID number on an LCD for example

please anyone have an idea how to read barcode reader and display on LCD ?

A bit contradictory, dontcha think?

Anywhos...
Usually, I put my On Interrupt near the beginning of a program, and skip over it into my main program. Some say it's good practice, others say they don't care, and still others say it straightens out execution sometimes. I don't know, I just know it works for me.

So, assuming you really have a good handle on your hardware and how the barcode scanner actually works, then this little bit of a rewrite should work for you.
(yes it's all crammed together, that's just the way I roll, you can reformat it all you want)

<-----LCD & Other DEFINES.....
<-----
clr con 1 : line1 con 128 : line2 con 192 : line3 con 148 : line4 con 212
ins con 254 : scl var portc.3 : sda var portc.4 : clock_barcode var portb.0
data_barcode var portb.1 : input clock_barcode : input data_barcode
output portd.1 : but1 var portb.2 : input but1 : portd.1 = 0 : option_reg = 5
pause 2000 : intcon = $90 : addr var byte : char var byte
ee_byteout var byte : ee_bytein var byte : id var bit[250]
countstep var byte : counter var byte : counter = 0 : trisd = 0 : ee_byteout = 0
On Interrupt Goto reg_id
goto mainloop
DISABLE ' Disable interrupts in handler
reg_id:
intcon.1 = 0
if clock_barcode=0 then   ; test falling edge
    id[counter]=data_barcode
endif
counter=counter+1 : portd.1=data_barcode
RESUME ' Return to main program
ENABLE ' Enable interrupts after handler[/QUOTE]
mainloop:     lcdout Ins,clr,Line1,"Please Ins. ID card"
Main:
if but1=0 then
    lcdout ins,clr,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

And it looks to me as if the whole code isn't here...

[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