LCD setup

[ruijc]

Hi guys,

i'm changing my lcd wires from the stardard configuration but i'm not getting this to work ( maybe it's too late and cant think right ) !!!

The idea is to:
lcd RS to pic RA4
lcd E to pic RB4
lcd DB to pic RB0,RB1,RB2,RB3

i'm using these defines:

Define LCD_DREG PORTB
Define LCD_DBIT 0
Define LCD_RSREG PORTA
Define LCD_RSBIT 4
Define LCD_EREG PORTB
Define LCD_EBIT 4

thanks

[nomad]

you show RS on pin ra4 but define says rsbit 3. also typically ra4 is open collector or open drain as an output and will need a pullup resistor. which pic are you using?

[nomad]

hey no fair you changed it while i was posting. lol. ok so that leaves the pullup issue.

[ruijc]

hehehe...

sorry nomad,

right now i'm slow thinking, but i got there ;)

i'm using a 16F628.
Also have a pullup 100K resistor...but still not working...

.

[nomad]

100k might be to large. too weak a pullup. i usually see 10k or even 4.7k as the pullup. check your input/output trisA settings and disable comparators, cmcon=7? ra4 is tied to cmp2.

[nomad]

oh yeah, also make sure the R/W line isn't left floating. needs to be grounded i believe. did you set 4 bit mode? DEFINE LCD_BITS 4. thats all i can think of without having the data sheet here or seeing the code. hope that helps.

[ruijc]

Hi nomad,

i think i know what's going on !

the thing is that i moved the stardard configuration to give me the RA0 and RA1 free and use them for analog input.

I have my code set for all PORTa to be input and analog...dahhh ( therefore the lcd RS to pic RA4 is not working )

TRISA = %11111111 ' Set PORTA to all input
ADCON1 = %10000010 ' Set PORTA analog and right justify result

This is why it doesnt work.

I need to set ONLY PORTA 0 and 1 ports analog and not all.

I will remove the first line ( trisa = %1111111 ) because it doesnt make any sense.

About the second line : ADCON = %10000010...

how can i set only RA0 and RA1 analog and the rest of the portA digital ?

thanks

[nomad]

You need the TRISA line. each bit determines input or output. so if you want ra4 as an output you need to change trisa to %11101111 also need cmcon=7 to disable the comparators. I dont have a data sheet to see what you need for adcon1 but the analog is for input only, and doesn't apply to a pin set to output. (as far as i understand) i think the cmcon and trisa lines should do the trick.

[nomad]

check this thread http://www.picbasic.co.uk/forum/showthread.php?t=561&highlight=16f628+ansel

[mister_e]

you may have some problem with 16F628 and ADCON1... as it don't have any a/d converter.

While it's always a good programming practice to set TRIS register, LCDOUT do it for you.

Faulty i/o
No contrast pot on LCD Vo line
R/W pin not tied to GND
no pull-up (~10K) on OpenCollector output
floating MCLR input if used, or not disabled in code
same thing for LVP mode,
faulty/missing connections
unsufficient LCD startup time

are some things to check.

[nomad]

Didn't know that about lcdout. Learn something new each day lol. That explains why i couldn't remember the settings for adcon1. Thanks MisterE.

[ruijc]

Thank you all for the help.

I started again from scratch and did some experiments moving the RS and E lines arround and all worked fine.
Now i have to sucessfully move the data bus to Portb.

I did not have the time yet to do so, but i will keep this thread updated.

In other hand, i've just realised that i will not able to finish this project because the 16F628 does not have the A/D converter i need to measure temp. - seen the analog input and assumed that it also had A/D :s ( Thanks Mister_E ).

Have to go and buy some 16F88s.

.