Comunication between PIC16f877A and PIC16f877A ?

[iugmoh]

Thanks duncan303 for your feeling with me,

I'm untill now working on a project for queuing system , which have 18 digits of seven segment and PS/2 barcode reader and printer and serial eeproms and other buttons and LCD
The objective of this system is :
1- Student must insert his ID card in barcode reader to get his ID number
2- Microcontroller check its number and look for his information on serial eeprom
3- Microcontroller decide to print his information and serially number on a sheet of paper
4- Student must wait for his number untill it's display on seven segment
5- After that Employee give student the requested service and press on a button to take another number of student

I completed untill now the barcode and the printer stage but I think that the pins of PIC16f877a is not enough so I need another PIC so I worked on this stage.

[duncan303]

Hi again

I was curious as to whether my choice of words might be understood

I also understand that it not actual programming that you need help on but the physical architecture of your proposed project for school, and that you may have run out of I/O pins. You could implement a port expander using a 74LS164 accessed serially that would give you 8 I/O's for every 2 used to control it.


You could consider making use of the hardware comms peripheral features that this chip has.

The difficulty is that your information is still far too vague, for me anyway. It would be useful to list which pins you have connected to what and how you are implementing your existing layout. And exactly what you want to add, ie I have three I/O pins left how can I add a 16 button keypad.

ie I have a printer connected to PORTA I have my LCD connected to PORTB I have my barcode reader connected to PORTC and my button connected to PORTD

Do you have a schematic you could post, or even a photo of your existing work in progress. Perhaps a photo of a quick pencil sketch, a picture speaks a thousand words in any language.


Duncan

[iugmoh]

thanks again for your gold idea 74LS164 which expanding our ports and not to need another PIC .
oky here is the pins and ports are used
- I use portc as data port for printer
- I use RB0 and RB1 for barcode one for clock and other for data
- I use RB3 for busy signal of printer
- I use RB2 for strobe signal of printer
- I use RB4,RB5,RB6 as buttons for registration and financial and cancel for student select

here is what used for the first stage
second stage I will control of 18 seven segments and need also 6 buttons for employes and one pin for indication sound

But I have a strange problem when I add in some way an addition code in our programm , I notice that the intrrupt is not working well

here is the code I added in the begining of our programm
;;;;;;;;;; check the availability of printer
lcdout ins,clr,ins,line1,"Check Printer...."
if busy=1 then
while busy=1
LCDout ins,line2,"Printer Problem"
wend
endif

LCDout ins,line2,"Printer Online"
pause 2000

lcdout Ins,clr,INS,Line1,"Please Ins. ID card"
;;;;;;;;;;;;;;;;;;;;;;;;;
I don't know what is the problem ???????????

[duncan303]

so you have PORTA and PORTD completely free?

why exactly have you run out of I/O's

shortly about to leave to catch "the learning curve" by Libby Purves on Radio 4, tonight has a piece about the government OFSTED inspections that are due very soon, do you have the same sort of thing?

Duncan