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otavio_fisica
Joined: 20 Jul 2006
Posts: 29
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| LCD 16x2 doesn't receive last bit |
 Posted: Tue Jul 17, 2007 6:09 am |
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Hi everyone.
I have a problem when trying to use a 16X2 lcd with the CCS lcd driver. I have already verified all the connections, but they are all ok. I wrote the following lines:
| Code: | #include <16F689.h>
#device adc=8
#FUSES NOWDT //No Watch Dog Timer
#FUSES XT //Crystal osc <= 4mhz
#FUSES NOPROTECT //Code not protected from reading
#FUSES NOBROWNOUT //No brownout reset
#FUSES NOMCLR //Master Clear pin used for I/O
#FUSES NOCPD //No EE protection
#FUSES NOPUT //No Power Up Timer
#FUSES NOIESO //Internal External Switch Over mode disabled
#FUSES NOFCMEN //Fail-safe clock monitor disabled
#use delay(clock=4000000)
#include <lcd.c>
void main()
{
lcd_init();
printf(lcd_putc,"\fabcdefghklmnopqr");
while (true){
output_high(PIN_B7); //this is a led pin
delay_ms(100);
output_low(PIN_B7);
delay_ms(100);
}} |
but the result I got in the LCD was "`bbddffhjllnn``b" instead of "abcdefghklmnopqr". I've consulted the ascii table and I realized that the binary code for "a" is "0110 0001" and the code for "`" is "0110 0000", i.e., the difference is in the last bit. It should be sent as a 1, but it was sent as a 0. This happens for the other letters and it is interesting that the code for "p" is "0111 0000". The only difference between "p" and "`" is the last bit for the first part of the byte. The same for the "q" and the "r". So, as the driver sends by nibble mode, I suspected that there might be a problem with the connection of the last pin bit. But, it is ok!!
I don't know what to do. Does anyone have any suggestion?
I use PIC16F689 and the connections are the following:
PIN_C4-->LCD_D4
PIN_C5-->LCD_D5
PIN_C6-->LCD_D6
PIN_C7-->LCD_D7
PIN_C0-->LCD_EN
PIN_C1-->LCD_RS
PIN_C2-->LCD_RW
I tried the flexlcd driver already posted here. It didn't work. It hasn't showed anything. Even after changing the delay_ms(15) to a delay_ms(50).
The version of my CCS is
IDE 4.010, PCB, PCM and PCH 4.013.
I have searched the forum for a similar problem, but I still haven't found it. Any help would be of great value.
Thanks,
Otávio Gomes. |
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Bill Boucher
Joined: 04 Feb 2005
Posts: 34
Location: Chatham,ON,CA
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| Posted: Tue Jul 17, 2007 9:50 am |
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Add the following line to your powerup or initialization section:
| Code: | | setup_comparator(NC_NC_NC_NC); // kill comparators |
The 16F689 has comparators and they are on by default. The comparator output on PIN_C4 may be overriding your LCD data.
Good luck.
As follows:
| Code: |
void main()
{
setup_comparator(NC_NC_NC_NC); // kill comparators
lcd_init();
printf(lcd_putc,"\fabcdefghklmnopqr");
while (true)
{
output_high(PIN_B7); //this is a led pin
delay_ms(100);
output_low(PIN_B7);
delay_ms(100);
}
}
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otavio_fisica
Joined: 20 Jul 2006
Posts: 29
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| Posted: Tue Jul 17, 2007 1:46 pm |
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| Thank you very much. Now it works correctly. I knew there was something happening with the pin but I couldn't realize what it was... thank you again... very much. |
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