Hello everyone,

I'de like to share this project, may come handy for hobbyist working around LCD display.

My search for a serial LCD that can receive serial data from 300 to 19200 baud on the internet was not successful
then I roll-up my sleeves and build this LCD backpack that use a common Hitachi HD44780 display. (still popular today)

My project was simple with parts already on hand like PIC16F690, NPN smd transistor, potentiometer, resistor. and PBP3 Basic code.

So enjoy,

Code:
'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' Name  : 16F690 LCD BACKPACK
' Date  : Sep 27-2025
' Note  : 393 words used  of 2048
' Notes : Serin2 Baud Rate 300 ~ 19200 Intrc_OSC 8Mhz
'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
#CONFIG
cfg = _INTRC_OSC_NOCLKOUT 
cfg&= _WDT_OFF
cfg&= _PWRTE_OFF
cfg&= _MCLRE_OFF
cfg&= _CP_OFF
cfg&= _CPD_OFF
cfg&= _BOD_OFF
cfg&= _IESO_OFF
cfg&= _FCMEN_OFF
  __CONFIG cfg
#ENDCONFIG
DEFINE OSC 8        ' Core is running at EXT-CRYSTAL 16MHz PBP 33,217
ANSEL = 0           ' Set all pins digital
ANSELH = 0          ' Set all pins digital
OPTION_REG.7 = 0    ' PORTA/PORTB pull-ups are enabled by individual port latch values
CM1CON0 = 0         ' Analog comparators off


En var Portb.4 : low en
RS var Portb.6 : low rs
B1 var byte : b1 = 0


' 300=3313  600=1646  1200=813  2400=396  4800=188  9600=84  19200=32
BaudR var byte : baudr = 32 


TRISA = 0 : TRISB = 100000 : TRISC = 0
PORTA = 0 : PORTB = 0 : PORTC = 0
OSCCON = $70  


high Porta.0              ' Backlight ON


gosub LCDinit             ' initialise LCD


'Serin2
main:
    serin2 Portb.5,baudr,3,main,[b1]


    if b1 < 253 then     ' Characters
        PORTC = b1 
        HIGH EN : PAUSEus 5 : LOW EN
        goto main        
    elseif b1 = 254 then  ' LCD Command
        low RS            
        serin2 Portb.5,baudr,3,main,[b1]
        PORTC = b1          ' output the data
        HIGH EN : PAUSEus 5 : LOW EN
        high RS           ' character mode
        goto main         
    elseif b1 = 255 then  
        low rs            ' LCD Command


    serin2 Portb.5,baudr,3,main,[b1]
        if b1 = 0 then 
            low porta.0   ' Back Light OFF
        high rs
        endif
        if b1 = 8 then 
            high porta.0  ' Back Light ON
        high rs    
        endif
       goto main             ' loop back to top
    ENDIF


LCDINIT:                  ' Standard LCD Module Initialisation
PORTC = 000001          ' 2, Clear Display
    HIGH EN : PAUSEus 300 : LOW EN ' Send data
    pause 4
PORTC = 000010          ' 4, Return Home
    HIGH EN : PAUSEus 300 : LOW EN
    pause 4
PORTC = 111000         ' 1, 8 bit, 2 line, 5x8 Characters
    HIGH EN : PAUSEus 300 : LOW EN
    pause 4
' PORTC = 001100          ' Display on, no cursor, no blink
PORTC = 001110          ' 1, Display on, cursor, blink
    HIGH EN : PAUSEus 300 : LOW EN
    pause 4
PORTC = 000110          ' 1, Entry mode
    HIGH EN : PAUSEus 300 : LOW EN
    pause 4
    high rs                  ' character mode
RETURN

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