Manual

User’s Manual
Scott Edwards Electronics, Inc.
1939 S. Frontage Road, Suite F, Sierra Vista, AZ 85635 USA
ph: 520-459-4802 • fax: [phone] • www.seetron.com
BPI-216 • v1.2 • 07/00 • pg 5
byte 0
byte 1
byte 2
byte 3
byte 4
byte 5
byte 6
byte 7
bit 0 bit 1 bit 2 bit 3 bit 4
Byte Values
xxx00000
xxx00100
xxx00010
xxx11111
xxx00010
xxx00100
xxx00000
xxx00000
0
4
2
31
2
4
0
0
binary decimal
Defining Custom Symbols
Most of the LCD characters (figure 6) cannot be changed because they are stored in ROM. However,
the first eight symbols, corresponding to ASCII 0 through 7, are stored in RAM. By writing new values
to the character-generator (CG) RAM, you can alter these characters. Changing a symbol is easy; just
point to the beginning of the symbol’s RAM location, then write eight bytes whose bits form the desired
pattern. Then position the cursor onto the screen. See figure 5.
Manipulating custom characters allows you to create special effects, like simple animations. See serial
display application notes at www.seetron.com for examples and a handy visual character editor.
Figure 5. Defining custom symbols.
ASCII
Code
Base
Address
0 64
1 72
2 80
3 88
4 96
5 104
6 112
7 120
Bitmap Layout Symbol Locations Example: Loading the Symbol
To load the arrow shown at left to symbol 3,
a program would send the following bytes to
the LCD:
<254><88>
<0><4><2><31>
<2><4><0><0>
<254><128>
' Point to symbol 3
' Send the bit
' pattern
' Move cursor back
' to the screen
32 40 48 56 64 72 80 88 96 104 112 1200 160 168 176 184 192 200 208 216 224 232 240 248
0
1
2
3
4
5
6
7
NOTE: Custom characters occupy ASCII 0—7
Backpack loads patterns shown at startup.
ASCII 8—31 repeat the custom characters
ASCII 128–160 are blanks
To find the ASCII code for a given character, add the row and column numbers.
For example, capital D is in the column marked 64 in row 4, so its ASCII code is
68. Use the reverse procedure to determine the symbol for a given code. For
example, ASCII code 244 produces the symbol Ω, found at colum 240, row 4.
Figure 6. LCD character set.
<#> means a byte set to the value #.
See the program examples.