User manual

5) CUSTOM CHARACTERS

The LCD controller is great for ready-made alphanumeric characters: send the code for a

character in ROM, and it is displayed on the LCD. But there is also a very small amount of

RAM reserved for custom characters. The controller can hold up to 8 characters of your

own design. To create and display these characters, use the following procedure:

- Design your 5x8 character

- Code it into 8 bytes, one byte for each row

- Save the data in the controller’s ‘character generator RAM’

- Repeat above steps for up to 8 characters

- Display the character by sending the corresponding code (0x00 through 0x07)

Let’s try a useful example: a battery status indicator. We will create seven symbols, going

from no-charge to full-charge. Fill in the outline of the no-charge symbol, assigning a ‘1’ to

a filled square and ‘0’ to a clear square.

Here is the battery symbol on a 5x8 grid. There

are 8 rows, and each row has 5 columns. The

green box shows how we convert the binary

ones and zeros of each row to their

hexadecimal equivalent. Our 8-byte

representation for the symbol, from top to

bottom, is the list [0x1E, 0x1B, …, 0x1F]

To create a full-charge battery, just fill in the middle rows. As you fill each middle row, its

value will change from 0x11 to 0x1F. A list of all of these battery symbols looks like this:

battery = [

[ 0x0E, 0x1B, 0x11, 0x11, 0x11, 0x11, 0x11, 0x1F ], #0% (no charge)

[ 0x0E, 0x1B, 0x11, 0x11, 0x11, 0x11, 0x1F, 0x1F ], #17%

[ 0x0E, 0x1B, 0x11, 0x11, 0x11, 0x1F, 0x1F, 0x1F ], #34%

[ 0x0E, 0x1B, 0x11, 0x11, 0x1F, 0x1F, 0x1F, 0x1F ], #50% (half-full)

[ 0x0E, 0x1B, 0x11, 0x1F, 0x1F, 0x1F, 0x1F, 0x1F ], #67%

[ 0x0E, 0x1B, 0x1F, 0x1F, 0x1F, 0x1F, 0x1F, 0x1F ], #84%

[ 0x0E, 0x1F, 0x1F, 0x1F, 0x1F, 0x1F, 0x1F, 0x1F ], #100% (full charge)

]

Each row of this list corresponds to a battery symbol, from the no-charge symbol on top, to

the full-charge symbol on the bottom.

0b01110 = 0x1E

0b11011 = 0x1B

0b10001 = 0x11

0b11111 = 0x1F