AN #121 - Showing custom fonts on the T6963C

Graphic displays are great for projects that require both text and pictures to be displayed, but the text can be difficult to read on displays that have a small pixel size. An easy solution is to utilize the custom character generator that is built into the Toshiba tc6963 controller to generate a font that is bolder than the characters generated by the internal CGROM.

The software example was created using the Bascom-Avr compiler. Bascom-Avr has a set of built-in graphic LCD tools that make interfacing painless. The two commands: locate(x,y), and LCD are used to display text that is generated by the internal CGROM. The fist step in using custom characters is to create them. Each eight-byte line in the FONTC data table represents one custom character. Each character’s data file is created using the following format:

It is easy to understand how the characters are created and stored by looking at the above figure and comparing it with the FONTC table. After the data table is built, it must be stored in the LCD ram memory. The three steps needed to store the characters are: set- offset, set address pointer, and store characters. These routines access the library functions for the LCD that were included when the CONFIG GRAPHLCD command was invoked. Assembly language is used to interface with the library functions that are also written in assembly. The complier recognizes assembly lingo which makes it easy to include.

SET OFFSET- This step is need to set the address location where the characters are stored. The command is &H22 and the data is &H0003. This will set beginning of the custom character storage at memory location &H1C00.

SET ADDRESS POINTER- This step sets the pointer to &H1C00. This is where the FONTC table will be stored.

STORE CHARACTERS- This step is responsible for reading the FONTC table and writing it to the LCD ram starting at the location of the address pointer.

To print the custom characters to the LCD, you first set the cursor position with the locate(x,y). The text to be displayed is stored in the variable Btxt. After setting the cursor and storing the text in Btxt, call the sub routine TEXT with Btxt as the argument. The text to be displayed must be in CAPS. In this example letters A-Z and numbers 1-9 get the bold treatment.

This application adds some additional functionally for text display that is easy to implement. The large font is easy to read and is invoked by a simple sub-call. The ability to print both regular and bold text will allow for a more creative interface.

'////////program that demonstrates the use of user-defined characters/////////

'////////////////display used is a Toshiba 128*128 /////////////////

'!!!!!!!!! text passed to sub must be in all caps to work!!!!!!!!!!!!!!

$crystal = 4000000

Dim Gl_byte As Byte

Dim V As Byte

Dim K As Byte

Dim P As Byte

Dim W As Word

Dim Q As String * 1

Dim Btxt As String * 16 'string to be printed

Declare Sub Text(sf As String ) 'sub that prints the big text

Config Graphlcd = 240 * 128 , Dataport = Portb , Controlport = Portc , Ce = 2 , Cd = 3 , Wr = 0 , Rd = 1 , Reset = 4 , Fs = 5 , Mode = 8

Cls

Cursor Off

Wait 1

'set offset

ldi r24,&h03 'load r24 with offset location low byte

rcall _GWrite_Data

ldi r24,&h00 'load r24 with offset location high byte

Rcall _GWrite_Data

ldi r24,&h22 'set offset command

rcall _GWrite_Cmd 'write command to LCD

'set address pointer

ldi r20,&h00 'address that pointer will point to

ldi r21,&h1c 'set address pointer command

rcall _set_address 'set address routine

'store characters

Restore Fontc 'select fontc table

For W = 1 To 288 'read each fontc table byte into

Read Gl_byte 'read a byte from the table

Loadadr Gl_byte , X 'load register x with gl_byte address

ld r24, x 'load r24 with gl_byte

rcall _GWrite_Data

ldi r24, &hc0 'command to write and increment pointer

rcall _GWrite_Cmd

Next W

'display Character

Locate 2 , 1 'set cursor location

Btxt = "ABCDEFGHIJKLMNOP" 'set Btext with text to be printed

Call Text(btxt) 'call text sub

Locate 3 , 1

Btxt = "QRSTUVWXYZ"

Call Text(btxt)

Locate 4 , 1

Btxt = "0123456789"

Call Text(btxt)

End

'sub used to display characters

Sub Text(sf As String ) '!!!!!sf text must be in caps to work!!!!

V = Len(sf) 'get length of string

For K = 1 To V 'repeat until end of string

Q = Mid(sf , K , 1) 'read each character

P = Asc(q) 'convert to ascII

If P < 65 Then 'adjust ascII code

P = P + 106

Else

P = P + 63

End If

Loadadr P , X 'load x with address of p

ld r24,x 'load r24 with p

rcall _GWrite_Data 'write and increment

ldi r24,&hc0

rcall _GWrite_Cmd

Next K

End Sub

'///////////////////////////////////////character data /////////////////////////////////////////////

Fontc:

Data &H7C , &HFE , &HC6 , &HC6 , &HFE , &HFE , &HC6 , &HC6 'A

Data &HFC , &HFE , &HC6 , &HFE , &HFE , &HC6 , &HFE , &HFC 'B

Data &H7E , &HFE , &HC0 , &HC0 , &HC0 , &HC0 , &HFE , &H7E 'C

Data &HF8 , &HFC , &HC6 , &HC6 , &HC6 , &HC6 , &HFC , &HF8 'D

Data &HFE , &HFE , &HC0 , &HFE , &HFE , &HC0 , &HFE , &HFE 'E

Data &HFE , &HFE , &HC0 , &HFC , &HFC , &HC0 , &HC0 , &HC0 'F

Data &H7E , &HFE , &HC0 , &HDE , &HDE , &HC6 , &HFE , &H7C 'G

Data &HC6 , &HC6 , &HC6 , &HFE , &HFE , &HC6 , &HC6 , &HC6 'H

Data &HFE , &HFE , &H38 , &H38 , &H38 , &H38 , &HFE , &HFE 'I

Data &H7E , &H7E , &H18 , &H18 , &HD8 , &HD8 , &HF8 , &HF8 'J

Data &HC6 , &HCC , &HD8 , &HF0 , &HF0 , &HD8 , &HCC , &HC6 'K

Data &HC0 , &HC0 , &HC0 , &HC0 , &HC0 , &HC0 , &HFE , &HFE 'L

Data &H82 , &HC6 , &HEE , &HEE , &HD6 , &HD6 , &HC6 , &HC6 'M

Data &HE6 , &HE6 , &HF6 , &HD6 , &HD6 , &HDE , &HCE , &HCE 'N

Data &H7C , &HFE , &HC6 , &HC6 , &HC6 , &HC6 , &HFE , &H7C 'O

Data &HFE , &HFE , &HC6 , &HFE , &HFE , &HC0 , &HC0 , &HC0 'P

Data &H7C , &HFE , &HC6 , &HC6 , &HC6 , &HCE , &HFE , &H7E 'Q

Data &HFE , &HFE , &HC6 , &HFE , &HFE , &HF0 , &HD8 , &HCC 'R

Data &HFE , &HFE , &HC0 , &HFE , &HFE , &H06 , &HFE , &HFE 'S

Data &HFE , &HFE , &H38 , &H38 , &H38 , &H38 , &H38 , &H38 'T

Data &HC6 , &HC6 , &HC6 , &HC6 , &HC6 , &HC6 , &HFE , &HFE 'U

Data &HEE , &H6C , &H6C , &H6C , &H28 , &H38 , &H38 , &H10 'V

Data &HEE , &HC6 , &HC6 , &HD6 , &HD6 , &H7C , &H6C , &H6C 'W

Data &HC6 , &H6C , &H28 , &H38 , &H38 , &H28 , &H6C , &HC6 'X

Data &HC6 , &HC6 , &H6C , &H28 , &H38 , &H38 , &H38 , &H38 'Y

Data &HFE , &HFE , &H0E , &H1C , &H78 , &HE0 , &HFE , &HFE 'Z

Data &H3C , &H7E , &H66 , &H76 , &H6E , &H66 , &H7E , &H3C '0

Data &H38 , &H78 , &H98 , &H18 , &H18 , &H18 , &H18 , &H7E '1

Data &H38 , &H6C , &H6C , &H0C , &H18 , &H30 , &H60 , &H7C '2

Data &HFE , &HFE , &H06 , &H7E , &H7E , &H06 , &HFE , &HFE '3

Data &H18 , &H38 , &H78 , &HD8 , &HFE , &HFE , &H18 , &H18 '4

Data &H7C , &H60 , &H78 , &H4C , &H0C , &H0C , &H4C , &H38 '5

Data &H1C , &H30 , &H60 , &H78 , &H6C , &H6C , &H6C , &H38 '6

Data &H7C , &H4C , &H0C , &H0C , &H18 , &H18 , &H18 , &H18 '7

Data &H38 , &H6C , &H6C , &H38 , &H6C , &H6C , &H6C , &H38 '8

Data &H38 , &H6C , &H6C , &H6C , &H3C , &H0C , &H18 , &H70 '9