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maisy
Joined: 01 Apr 2011
Posts: 3
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| LCD display Question marks(?) instead of card ID |
 Posted: Fri Apr 01, 2011 4:38 am |
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Hi,
I face problem in reading LCD display from RFID reader. There is nothing show when +5V is supply (should display "TEST"). Once i scan card on reader, 10 question marks are displayed.
S/W: PCWH compiler v4.038
H/W: PIC16f877a, 2x16LCD, RFID-IDR-232N (Baud rate:9600, 1 byte Start of heading (0x01), followed by 10 byte of ASCII character (ID) and 1 byte of Start of text (0x02))
Attach with my coding below:
| Code: | #include <16F877A.h>
#fuses HS, NOWDT, NOPUT, NODEBUG, NOLVP, NOBROWNOUT, CPD, PROTECT, NOWRT
#use delay(clock = 20000000)
#include <FLEXLCD2.C>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#use fast_io(B)
#priority RDA
#define LCDlight PIN_C1
//#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7)
#use RS232(BAUD=9600, XMIT=PIN_C6, RCV=PIN_C7, STREAM=COM_A)
#use rs232(baud=9600, xmit=PIN_D2, rcv=PIN_D3, STREAM=COM_B) //only PIN_D3 is connected)
#priority RDA
#zero_ram
int header, end, buffer[10]={}, counter=0;
int1 RFIDscan_fl=0;
////////////////////////////////////////////////////////////////////////////////
#INT_RDA //RS232 receive data available
void isr_rs232(){
header = getc();
if (header == 0x01){
while(counter<10){
buffer[counter] = getc();
counter++;
}
counter=0;
end = getc();
if(end == 0x02){
RFIDscan_fl=1;
}
}
}
void checkIncomingData(){
if(kbhit(COM_B)){
if (fgetc(COM_B) == 0x01){
while(counter<10){
buffer[counter] = fgetc(COM_B);
counter++;
}
counter=0;
end = fgetc(COM_B);
if(end == 0x02){
RFIDscan_fl=1;
}
}
}
}
void display_lcd(){
lcd_putc("\f");
lcd_putc(buffer[0]);
lcd_putc(buffer[1]);
lcd_putc(buffer[2]);
lcd_putc(buffer[3]);
lcd_putc(buffer[4]);
lcd_putc(buffer[5]);
lcd_putc(buffer[6]);
lcd_putc(buffer[7]);
lcd_putc(buffer[8]);
lcd_putc(buffer[9]);
}
//###################################### main program started ##################
void main() {
lcd_init();
output_high(LCDlight);
lcd_putc(" TEST \n");
delay_ms(1000);
while (1) {
checkIncomingData();
if(RFIDscan_fl==1){
display_lcd();
RFIDscan_fl=0;
}
}
}//main() |
Should i attach coding for FLEXLCD2.C?
Thanks! |
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temtronic
Joined: 01 Jul 2010
Posts: 9246
Location: Greensville,Ontario
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| Posted: Fri Apr 01, 2011 6:28 am |
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couple of points....
delete the USE FAST_IO(B)..
..let the compiler handle the DDRs
add 'errors' to the USE RS232(..)..
..let the compiler handle the serial port
does the rfid reader connect via ttl or true RS232 ?
..if RS232, do you have a MAX232 or equal wired in right?
have you hooked up the reader to ,say , a PC and confirmed it works ? |
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maisy
Joined: 01 Apr 2011
Posts: 3
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| Posted: Fri Apr 01, 2011 8:56 am |
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Thanks for your reply.
1) Due to the FLEXLCD2.C, i have to use fast_io(B).
http://www.ccsinfo.com/forum/viewtopic.php?t=24661
2) I have change to code as below:
| Code: | #use RS232(BAUD=9600, XMIT=PIN_C6, RCV=PIN_C7, STREAM=COM_A, errors)
#use rs232(baud=9600, xmit=PIN_D2, rcv=PIN_D3, STREAM=COM_B, errors) |
3)The rfid reader is connect to MAX232 through MCU, but MAX232 is not connected to PC. Actually i already test each of the module on breadboard. After they really work fine, then only i switch to PCB. I have check the connection so many times and should not be h/w problem.
4) I wonder why the lcd display nothing (even no black square,only back light is on) when i run the simple "LCD_display" programming that provided from PCM programmer. But whn i scan the reader, lcd can display question marks. |
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temtronic
Joined: 01 Jul 2010
Posts: 9246
Location: Greensville,Ontario
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| Posted: Fri Apr 01, 2011 9:18 am |
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hmmm... I don't have FLEXLCD2.C driver, just the flexlcd.c driver and use standard_IO mode fine.
sounds like the LCD is not getting initialized or setup correctly then 'gets in sync' later.
might be quirk of the display you're using, or something different in lcd_init() from my version... |
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ckielstra
Joined: 18 Mar 2004
Posts: 3680
Location: The Netherlands
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| Posted: Sat Apr 02, 2011 4:56 am |
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From the specified thread: | Quote: | Disadvantages or Limitations:
1. This driver requires CCS "standard i/o" mode (The default mode
of the compiler). If you want to use fast i/o mode, then use the CCS
driver or Mark's driver: |
I have not scanned all 7 pages of the linked thread, but I assume your FLEXLCD2.C file is the program listed at the top first page?
If yes, then you should not use fast_io. |
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maisy
Joined: 01 Apr 2011
Posts: 3
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| Posted: Sat Apr 02, 2011 8:14 am |
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Hi ckielstra,
Yaya, you are right! Thanks for your correction. I am so blur. However, the coding works fine on breadboard so i never suspect.
After re-wire hardware and found that no voltage supply to LCD. But i wonder why LCD can perform blinking function and display question marks without voltage supply.
All,
Now, my project work as expected. Sorry in wasting your time for my careless mistake. Thanks for all replies  However, I have learn a lot from this forum throughout the issue. This forum is awesome! |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19553
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| Posted: Sat Apr 02, 2011 10:08 am |
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With almost all IC's, there are either deliberately for protection, or 'accidentally' because of the structure of the gates involved, effectively diodes on the input lines, that prevent an incoming signal, from going significantly above the devices 'supply'. Because of this, if you connect such a device, that does not need too much power, to a series of logic lines carrying signals, while leaving the supply disconnected, the signals will tend to 'pump' the rail inside the device up, often to the point where it'll start to work. If there is some capacitance attached to the device, this allows the 'gaps' in the signals to be bridged. 'Partial' operation, can then result. How well it'll actually work, will depend on the available current on the signals, the exact pattern of the signals, the consumption of the device, luck, etc....
So the processor was actually supplying the power for your LCD, with slightly 'indeterminate' results....
Best Wishes |
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