DAN128

Build a Serial LCD

  By Michael Simpson

You can build a very fast and functional serial LCD using just the Dios.  The default baud rate is 9600 but you can set it to just about any thing you want.   See the hsersetup command.

Dios Carrier 4

The hookup is simple.  You can change the LCD control pins if you wish.  Just remember to change the LCDinit function.  Also your LCD may need to have a contrast trimmer or backlight connection.

We will only be using one pin to connect to the serial LCD.  If you need to transmit data from the serial LCD to the microcontroller.  You will need to connect P8 as well.

Dios Ultra Notes

After Programming the Dios Ultra You can change the RS232 Jumpers.   This will allow you to connect RS232 Level data into the 9 pin programming port.

The Program (Download it here)

'This program will turn the Dios into a serial LCD.
func main()
   dim inchar as integer
   dim cmd as integer
 

   'Dios Ultra

   LCDinit(23,25,24,29,28,27,26) 'RS, E, RW, D0,D1,D2,D3

   LCDcls()
   LCDcharxy(1,1,"Kronos Robotics")
   LCDcharxy(2,1,"Serial LCD v1.0")
   pause 1000
   LCDcls()
   hsersetup baud,HBAUD9600,start
   cmd = 0

mainloop:

   hserin mainloop,inchar
   branch cmd,cmd0,line1,line2,line3,line4,control,raw

'----------------------------------
'Fall through point
'----------------------------------
cmd0:
   if inchar < 7 then
      cmd = inchar
      goto mainloop
   endif
   LCDraw(inchar)
   goto mainloop

'---------------------------------
'1,x Select character on line 1
'---------------------------------
line1:
   LCDgoto(1,inchar)
   cmd = 0
   goto mainloop

'---------------------------------
'2,x Select character on line 2
'---------------------------------
line2:
   LCDgoto(2,inchar)
   cmd = 0
   goto mainloop

'---------------------------------
'3,x Select character on line 3
'---------------------------------
line3:
   'Reserverd for future use

'---------------------------------
'4,x Select character on line 4
'---------------------------------
line4:
   'Reserverd for future use

'---------------------------------
'5,x Send LCD control codes
'---------------------------------
control:
   LCDcontrol(inchar)
   cmd = 0
   goto mainloop

'---------------------------------
'6,x Send characters 0-6
'---------------------------------
raw:
   print "raw =",inchar
   LCDraw(inchar)
   cmd = 0
   goto mainloop

endfunc

include \lib\DiosLCD.lib

The program uses the interrupt driven UART in the Dios.  All the work is done behind the scenes so you don't have the mess with the details.  The Dios is set up with a 256 byte buffer.   So it can take quite a bit serial pounding.

The hserin command just checks the buffer for any characters.  If no characters are in the buffer the command jumps to the mainloop.

If a character is received the hserin command falls through so you can process the character.

The program uses a state machine to keep track of the current state command state.  The actual state is stored in the variable cmd.  When a character is received we branch to the correct handler to process the data.  If we are in state 0 then we set the correct state if its 1-6 and continue on.

Some code examples for sending to the Serial LCD.

serout IOpin,1,1,"Hello World"

serout IOpin,5,1     'Clear the LCD

There is a lot of room for expansion in the program.  Here are a couple of ideas.

• Add counter to main loop that resets then state to 0 if threshold is reached.

• Add Analog to digital ports

• Add button or keyboard interface

• Add ability to change baud rate.  Current baud rate is 9600.

• Add the ability to set line positions 3 and 4 for 4 line LCD.

Test Programs

here is a test program that will test most aspects of the Serial LCD.  This will show you the kind of Dios commands needed to communicate with the Serial LCD

Get it here

Here is the same program with all the pause statements removed so that you can see what kind of speeds you can get out of this serial LCD.

Get it here

Parts list

 

 

DiosPro 40 Pin Chip

Dios Workboard Deluxe

 

Easy RS232 Driver  

DiosPro 28 Pin Chip

Dios 32 Pin Carrier (Carrier #1)

 

9 Pin Cable

Breadboard Regulator