PORT A and PORT B using LCD

[cobra1]

Hi Guys

I am having a problem with an LCD im using,

I made a PCB origionally to use the LCD on PORT A, on the latest version of PCB i changed it to PORT B as it was easier to lay out.

Now the problem is that on PORT B it doesnt work properly, it will display a splash screen but after that, the display becomes corrupted and will not display text.

Im using a PIC 18F26K20 and the LCD uses a ST7565R chipset, wired for serial use. (5 wires)

Ok, the question, is PORT A and different to PORT B??
Also why would i be experiencing corruption using PORT B but not PORT A??

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[AtomSoft]

Did you CLEAR ANSELH ? PORTB has INTERRUPTS and PULLUPS

 

[cobra1]

Im not sure, i use flowcode for coding because im a bit thick when it comes to C. I set PORT B to digital I/O on reset if thats what you mean.

Do you have any idea why it will display some things but not others??

 

[AtomSoft]

sounds like a interrupt issue like its triggering when it feels like

 

[cobra1]

RB0, RB1, RB2 are control lines, RB3, RB4 are data and clock.

Is there anything i can do to correct the problem? failing that its another PCB design back to PORT A i think.

 

[AtomSoft]

I never used flow code. Try to disable all interrupts on PORTB

 

[cobra1]

how would i do that in C? i can add in supplimental code

 

[AtomSoft]

try this:

INTCON = 0x00; //No interrupts
INTCON2 = 0x80; //No pullups
INTCON3 = 0x00; //No Interrupts (again) just in case

 

[cobra1]

Hi, i added that code in, but no luck, just does exactly the same thing.

Im just totally confused as to why it is doing this as all i have done is changed the 5 lines to a different port.

 

[AtomSoft]

silly question are you sure you set all the old PORTA to PORTB ? Maybe you missed some ? Can you post code ? is there a demo of this flow code program ?

Found the demo, do you have version 3 or 4 ?

 

[cobra1]

Yeah i changed the port over to PORT B, heres the code:

//Flowcode Defines
#define MX_CONTROL_PORT			portb	//%a
#define MX_CONTROL_TRIS			trisb	//%b
#define MX_CS1				0	//%c  - CS1
#define MX_CON_RES			1	//%d	- RST
#define MX_DAT_INST			2	//%e	- A0
#define MX_SCLK				3	//%f	- SCLK LCD-D6
#define MX_SDATA			                4	//%g	- SDATA LCD-D7

This is the only part that requires changing to set ports

heres what im getting just trying to print the number 23

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[AtomSoft]

are you sure thats all you changed ? looks like a timing or miss alignment more than it not working

 

[cobra1]

yeah thats all, if i change it back to porta, trisa. i can use that on another board i made perfectly, obviously it uses PORT A instead for the LCD

 

[cobra1]

Same model LCD on a different board using PORT A

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[AtomSoft]

thats crazy, heh this might sound even crazier ... have you tried replacing the MCU ?

 

[cobra1]

yeah tried that too, i even built a second board up to try, using my last LCD both do exactly the same thing,

I have 50 of these boards, i didnt think this would be an issue when i had them made.

 

[AtomSoft]

wow! this is a weird issue tho. PORTB should be technically the same.

Im reading the datasheet and only difference i see is...PORTB has the below which PORTA doesnt have:

Interrupts
Internal Pullup Resistors

it seems like your program is working meaning the LCD is getting data but not all the time. or at the right time.
perhaps its a hardware issue. are there any resistors you might have forgotten to move from PORTA to PORTB like

for the CS, SCL,SDA lines ? Is this a SPI LCD ? may i ask where did you get it from. It looks so cool!

 

[cobra1]

The LCD can be used in both parallel or serial, im using serial/SPI

I dont have any resistors on either of the ports so nothing to move, the LCDs are from NEWHAVEN DISPLAY

 

[cobra1]

I guess im gonna have to bite the bullet and redesign the board using PORT A again.

 

[AtomSoft]

wow just wait... im sure other people will also try to help.

ah you have one of these:
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