4-line LCD Help - using PortA instead of B

[Tom Gonser]

I have a 4-line LCD with 16 pins, the pin-outs seem to match use of the LCDOUT command.

I am using PortB, tho, and have to use PortA.. (0-3 for data lines, and 4,5 for the other two).. I have it setup as follows:

Define LCD_DREG PORTA
DEFINE LCD_DBIT 0
Define LCD_RSREG PORTA
Define LCD_RSBIT 4
Define LCD_EREG PORTA
Define LCD_EBIT 5
Define LCD_BITS 4
Define LCD_lines 4
Define LCD_Commandus 2000
Define LCD_Dataus 50

However, when I write out using $fe, LCDOUT, - I get nothing.... Any thoughts?

Thanks,
Tom

[NavMicroSystems]

Tom,

see: here

Let us know what brand and model of display you are using.

If it is more than 20 chars per line it is a dual controller display.

It could also be one of the "extended temperature range" models that require a negative voltage on Vee.

What does your hardware setup look like in detail?

You don't want us to guess, do you?

[Tom Gonser]

Sorry!! ;-o

The details - of course!

Crystalfontz 20x4 display - CFAH2004L-YYB-JP. 16 pins LED backlight

1 VSS 0V Ground - Vss
2 VDD 5.0V Supply Voltage for logic -> 5v
3 VO (Variable) Operating voltage for LCD -> I have this pinned to 5V
4 RS H/L H: DATA, L: Instruction code -> to RA4
5 R/W H/L H: Read(MPU→Module) L: Write(MPU→Module) -> to Vss
6 E H,H→L Chip enable signal -> to RA5
7 DB0 H/L Data bit 0 - NA
8 DB1 H/L Data bit 1 - NA
9 DB2 H/L Data bit 2 - NA
10 DB3 H/L Data bit 3 - NA
11 DB4 H/L Data bit 4 -> RA0
12 DB5 H/L Data bit 5 -> RA1
13 DB6 H/L Data bit 6 -> RA2
14 DB7 H/L Data bit 7 -> RA3
15 A - LED +
16 K - LED -
17 Vee
18 NC

I have this hooked to PORTA instead of PORTB because I am using some on PortB, but per earlier post, it seems everything is in place. I just get no data appearing on the screen.

Maybe I have to turn off some register of PortA on the 16F876/A that I don't know about..

--------------------------------------------------------------------------
' 16F876/A

Include "modedefs.bas" ' Include serial modes

ADCON1 = 7

define LCD_DREG PORTA ' Set data pin of LCD to
define LCD_DBIT 0 ' PORTB.0-PORTB.3

define LCD_RSREG PORTA ' Set RS bit of LCD to
define LCD_RSBIT 4 ' PORTA.4

define LCD_EREG PORTA ' Set E bit of LCD to
define LCD_EBIT 5 ' PORTA.5

DEFINE LCD_LINES 4 ' 4 Lines LCD
define LCD_COMMANDUS 2000 ' Command delay time in uSec
DEFINE LCD_DATAUS 100 ' Data delay time in uSec


lcdout $fe, 1
lcdout $fe, 2
LCDOUT "Hellow World"
pause 2000

I have seen others with this unit get success with PBP.. just not me yet..

TG

[anj]

You didnt mention it soooo, Do you have a pullup resistor on RA4?
Read PICmicro MCU specific Issues in the manual ( sect 2.5.1 )

Andrew

[Tom Gonser]

Yes, 4.7k ohm on R4..

[mister_e]

i didn't have any of those LCDs in stock but, can you place a trim pot on Vo pin. or just tie it to ground to see if you get at least some black square on???

Some LCD may need to place unused data pin to ground. Refer to your datasheet for that.

try removing thos DATAUS COMMANDUS defines
try a 2 secondes startup delay