serial LCD display?

Hello everbody,
Iam Interested in constructing a serial lcd display like the commercially available back pack.I tried using the serin command of Pic basic to receive the items( string of characters ) and display it on a 16*2 lcd Hitachi module in the 4 bit mode.It displayed junk.I was successful in displaying single variable but not string.can any one help me ? can any one give code example with serin2 with over flow pin,str(string variable).Preferably on pic16f84.A good explanation on its working will greatly be appreciated.
Thanks.
ra68gi.

Hi,

The PIC is to slow to manage the seriel communication and the LCD-work in software !
You have to use an hardware-UART !
Try to use also an 32-byte-ringbuffer for the received data (Interrupt-service-routine in assembler).
I realized the same with an I2C-communication on a 16F872. The PIC is to big, but it is one of our "favorites".

Look at the melabs site.
I know they have some examples for the lab X1 board and they may have it for others.
Victor

I did this with a 'F88 - worked fine at 2400 baud (at 4MHz XT) so it should work fine on a 'F84/'F84A

I had it storing stuff in a buffer until it saw a chr$(13), then sending it all out to the LCD in one go...

Here's my code:

'Serial Control LCD
'for 24-char x 2 line display
'Serial data in at 2400 baud on PA0
'LCDout connections:
' PB0-PB3: DB4-DB7 ON LCD
' PB4: RS ON LCD
' PB5: E on LCD
' PB6: active high LCD backlight output
' R/W on LCD must be connected to GND
'
'Serial mode depends on the status of PA1 on powerup
' PA1=0:non-inverted mode (pic-to-pic)
' PA1=1:inverted mode (RS-232)
'
'turn the LCD backlight on/off by sending <1><13> or <0><13> respectively

DEFINE LCD_DREG PORTB 'set LCD data port
DEFINE LCD_DBIT 0 'Set starting Data bit (0 or 4) for 4-bit bus
DEFINE LCD_RSREG PORTB 'set LCD register select port
DEFINE LCD_RSBIT 4 'set LCD register select BIT
DEFINE LCD_EREG PORTB 'set LCD enable port
DEFINE LCD_EBIT 5 'set LCD enable bit
DEFINE LCD_BITS 4 'LCD bus size (4 or 8)
DEFINE LCD_LINES 2 'number of lines on LCD
DEFINE LCD_COMMANDUS 2000 'set command delay time in microseconds
DEFINE LCD_DATAUS 50 'set data delay time in microseconds
'
sermode VAR BYTE
mybyte VAR BYTE
pointer VAR BYTE
sendline VAR BYTE[24]
'
TRISA=63 'all inputs
TRISB=255 'all outputs
'note: pulldown PB3 if using 16F88
High PORTB.6

'read PA1 on powerup to determine mode
'jumper to ground for PIC-PIC communication (non-inverted, non-driven)
'jumper to + for RS-232 communication (inverted, driven)

IF PORTA.1=0 Then
sermode=0
Else
sermode=4
EndIF

Pause 1000 'initial pause before using the LCD
LCDOut $FE,1,"Display Initialized" 'clear display, send message
IF sermode=0 Then
LCDOut $FE,$C0,"PIC mode @2400 baud"
Else
LCDOut $FE,$C0,"RS-232 mode @2400 baud"
EndIF

Pause 2000 'wait 2 seconds
LCDOut $FE,1 'clear display again

NEWLINE:
pointer=0

GETMORE:
SerIn PORTA.0,sermode,,mybyte 'get 1 byte at a time
IF mybyte = 13 Then GoTo processme
sendline[pointer] = mybyte
pointer=pointer+1
GoTo getmore

processme:
IF pointer=1 AND sendline[0]=0 Then
Low PORTB.6 'turn off the LCD light if <0><13>
GoTo newline
EndIF

IF pointer=1 AND sendline[0]=1 Then
High PORTB.6 'turn on the lcd light if <1><13>
GoTo newline
EndIF

IF pointer=2 AND sendline[0]=$FE Then
IF sendline[1]=$01 Then 'clear display
LCDOut $FE,1
EndIF
IF sendline[1]=$02 Then 'return home
LCDOut $FE,2
EndIF
IF sendline[1]=$0C Then 'cursor off
LCDOut $FE,$0C
EndIF
IF sendline[1]=$80 Then 'beginning of first line
LCDOut $FE,$80
EndIF
IF sendline[1]=$C0 Then 'beginning of 2nd line
LCDOut $FE,$C0
EndIF
GoTo newline
EndIF


LCDOut STR sendline\pointer
GoTo newline
End

--------------Picster-------------

Picster,
Thanks for the code.I will soon try it out.I have a few more questions with regard to the code you have sent.
First,
' PA1=0:non-inverted mode (pic-to-pic)
' PA1=1:inverted mode (RS-232)

is there some sort of a convention to use non-inv mode for pic to pic & inverting mode for RS-232.
Please explain.

Second,
GETMORE:
SerIn PORTA.0,sermode,,mybyte 'get 1 byte at a time

I can see two comas after sermode.Is that right.
ra68gi

Quote:

---

Originally Posted by ra68gi

Picster,
Thanks for the code.I will soon try it out.I have a few more questions with regard to the code you have sent.
First,
' PA1=0:non-inverted mode (pic-to-pic)
' PA1=1:inverted mode (RS-232)

is there some sort of a convention to use non-inv mode for pic to pic & inverting mode for RS-232.
Please explain.

---

You must use inverted mode (through a resistor) if you're using RS-232 voltage levels (i.e. - to a PC serial port). For PIC-PIC serial communication, this is not necessary, you can merely use non-inverted, TTL levels.

Quote:

---

Originally Posted by ra68gi

Second,
GETMORE:
SerIn PORTA.0,sermode,,mybyte 'get 1 byte at a time

I can see two comas after sermode.Is that right.
ra68gi

---

Yes, because there is no "qualifier" to satisfy, you put 2 commas in as placeholders.

----------------------Picster----------------------