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LCD on port B and external interrupt B0 together

 
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benoitstjean



Joined: 30 Oct 2007
Posts: 553
Location: Ottawa, Ontario, Canada

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LCD on port B and external interrupt B0 together
PostPosted: Wed Dec 05, 2007 1:58 pm     Reply with quote
Just thought I'd share this info:

I usually use PORT B to drive an LCD display. I have a situation at the moment where I need to use external interrupt on port B0 along with the LCD display. In the LCD.C file provided by PICC compiler, I changed the pinout in the lcd struct to have B0 unused instead of the default (B3 I believe).

Anyhow, the problem I was having was when CCS's LCD driver accessed the LCD display, it would always make B0 an output and stop the external interrupt from responding.

I finally realized that the LCD.C file provided by CCS has one bit on the port that is unused. I changed it to be B0 but didn't realize that the set_tris_b function in the LCD.C file always set that bit to 0, so as output.

Anyhow, changing the bit to a 1 in the LCD.C file solved the problem. I realize it's not a big issue but when you don't think of it, then it's a different story. And if it can be of any help to anyone, then that's great.

Here are my modifications to the original file:
Code:

#define use_portb_lcd TRUE
struct lcd_pin_map
{                                       // This structure is overlayed
           BOOLEAN unused;   // on to an I/O port to gain
           BOOLEAN enable;   // access to the LCD pins.
           BOOLEAN rw;        // The bits are allocated from
           BOOLEAN rs;        // low order up.  ENABLE will
           int     data : 4;     // be pin B1.
        } lcd;

struct lcd_pin_map const LCD_WRITE = {1,0,0,0,0}; // For write mode all pins are out (except B0 which stays as input)

struct lcd_pin_map const LCD_READ = {1,0,0,0,15}; // For read mode data pins are in (except B0 which stays as input)
ateso3486
Guest
Thanks
PostPosted: Thu Jan 03, 2008 6:07 pm     Reply with quote
Thanks you saved my life Smile
I was in your situation. And because of lcd driver, my interrupts only worked for first time. Three days, i was trying to solve this. And this topic, i got the answer. Thanks a lot, benoitstjean.
Gaston



Joined: 05 Nov 2011
Posts: 1
Location: Argentina

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Excelent post !
PostPosted: Sat Nov 05, 2011 1:42 pm     Reply with quote
I know this post maybe a little old !.. BUT.. I was finding that info some hours ! Every day Everybody learns something new !

Thanks Bro !

Gaston from Argentina.
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