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John Morley
Joined: 09 Aug 2004
Posts: 97
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| Having trouble getting 8x2 LCD working with 16F689 |
 Posted: Wed Apr 11, 2012 4:24 pm |
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Hi All,
I recently upgraded an existing design from a 16F648A to a 16F689 because I needed a couple of additional I/O, and I wanted to take advantage of the higher speed internal oscillator available in the 16F689. Unfortunately, I can't get an 8x2 LCD to work with the new design. The top row is all solid squares like the LCD is not being properly initialized. I am using the Flex_LCD.c driver for this effort.
I've worked with character LCD's for many years, so of course I checked the power connections, and the Vee (contrast) voltage, and everything looks good. All the signal lines from the LCD to the PIC have been rung out, and an LED connected to each signal line at the LCD socket can be flashed. I even went so far as to connect a 16F648A to the new board using wire wrap wires, and the display works on the new board with the old PIC, just not with the 16F689 device. In short, my hardware seems to be OK.
The LCD is the only thing that is not working on the new design. I can flash diagnostic LED's at predictable rates/durations, and my serial Comms are working just fine, so I know that the 16f689 is basically working correctly.
I can run the following test program on the old design:
| Code: |
//-----< Include Files, setup fuses >-----
#include <16f648a.h>
#fuses INTRC_IO, NOWDT, NOPROTECT, NOLVP, NOBROWNOUT
// Tell compiler clock speed is 4.00 MHZ
#use delay(clock=4000000)
#include <flex_lcd.c>
//========================================
void main()
{
lcd_init();
lcd_putc("Hello 1\n");
lcd_putc("World 2");
while(1);
}
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With the following Flex_LCD pin connections:
| Code: |
#define LCD_DB4 PIN_A0
#define LCD_DB5 PIN_A1
#define LCD_DB6 PIN_A2
#define LCD_DB7 PIN_A3
#define LCD_E PIN_B3
#define LCD_RS PIN_A4
// If you only want a 6-pin interface to your LCD, then
// connect the R/W pin on the LCD to ground, and comment
// out the following line.
//#define USE_LCD_RW 1
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And everything works fine.
I cannot run the following test program on the new design:
| Code: |
//-----< Include Files, setup fuses >-----
#include <16f689.h>
#fuses INTRC, NOWDT, NOPROTECT, NOBROWNOUT, PUT
// Tell compiler clock speed is 8.00 MHZ
#use delay(clock=8000000)
#include <flex_lcd_689.c>
//========================================
void main()
{
lcd_init();
lcd_putc("Hello 1\n");
lcd_putc("World 2");
while(1);
}
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With the following Flex_LCD pin connections:
| Code: |
#define LCD_DB4 PIN_C0
#define LCD_DB5 PIN_C1
#define LCD_DB6 PIN_C2
#define LCD_DB7 PIN_C3
#define LCD_E PIN_B4
#define LCD_RS PIN_A2
// If you only want a 6-pin interface to your LCD, then
// connect the R/W pin on the LCD to ground, and comment
// out the following line.
//#define USE_LCD_RW 1
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And the code does not work at all.
I looked at the .lst file for each compilation with Beyond Compare, and they are very similar, except I think for the pin defines. There does seem to be a large block of code at the beginning of Main() for the new design that is not present in the old design, but it's not clear (to me) what it's doing?
I'm using a relatively old version of the PCM compiler, v4.050, and I'm wondering if something isn't being handled properly in this version for the 16f689 device? I'm very hesitant to blame the compiler, but the hardware seems to be OK.
If someone could take a look at the two .lst files and offer an opinion whether the compiler is generating the "correct" code, I'd be grateful. Any other suggestions are also welcome!
Thanks,
John
_________________
John Morley |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Wed Apr 11, 2012 5:24 pm |
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Try adding the lines shown in bold below, in the exact positions shown:
| Quote: |
#byte ANSEL = getenv("SFR:ANSEL")
//==========================
void main()
{
ANSEL = 0x00;
lcd_init(); |
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John Morley
Joined: 09 Aug 2004
Posts: 97
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| Posted: Thu Apr 12, 2012 6:30 am |
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Hi PCM,
I suspect that you are on to something here, but unfortunately my version of the compiler wasn't happy with that fix. The two added lines of code, added in the locations you indicated, resulted in the following errors:
| Code: |
*** Error 12 "LCD_Test_689.c" Line 14(1,2): Undefined identifier
*** Error 12 "LCD_Test_689.c" Line 17(7,12): Undefined identifier ANSEL
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I guess this means that my compiler is "unaware" of the ANSEL register location for this part, so the getenv() function wont work to find it? I think that means I should be able to hard code the address of this register from the datasheet, right? I'll take a look and see if I can figure that out!
John
_________________
John Morley |
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John Morley
Joined: 09 Aug 2004
Posts: 97
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| Posted: Thu Apr 12, 2012 6:41 am |
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Hi PCM,
OK, that was it! Your original hunch was correct!
This code solved my LCD problem:
| Code: |
#byte ANSEL = 0x11e
//========================================
void main()
{
ANSEL = 0x00;
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BTW, I had a similar thought about this issue, and tried adding this line of code to my original project, but it had no effect. It looks like v4.050 doesn't handle the ANSEL register correctly!
| Code: |
Setup_ADC_Ports( NO_ANALOGS);
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Thanks a million, and now I'm off to update my compiler!
John
_________________
John Morley |
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