LCD Display Drivers Lecture
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Transcript of LCD Display Drivers Lecture
Writing to an LCD
HD44780 LCD Drivers
16x1 LCD Module
16 characters, 1 row8-bit or 4-bit parallel interfaceIndustry standard HD44780 controllerVariations: backlight, polarizer, reflective, wide viewing angle.
http://www.crystalfontz.com/products/1601a/index.html#CFAH1601ANYGJP
HD44780U (LCD-II)
Dot Matrix Liquid Crystal Display Controller/DriverCan be controlled by 4- or 8-bit modeCan control up to one or two 8-character linesLow power supply (2.7V to 5.5V)5x8 and 5x10 dot matrix possible80 x 8-bit Display Data RAM (80 characters max)9,920-bit character generator ROM for 240 fonts
Interfacing to the LCD
Mapping Character Codes
to Character Patterns
Display Data RAM (DDRAM)
To write data to display, store individual characters into DDRAMLCD controller reads DDRAM and displays the data represented in 8-bit character codesCan store up to 80 characters16x1 can be implemented as a 2-line display of 8 characters (8x2) using same controller
Interfacing to the MCU
Pin Functions
Interfacing to the MCU
Interfacing to the MCU
4-bit mode: only DB4-DB7 used, two nibbles sent successively, high-order nibble first.
Instruction Descriptions
display clear – 20H to all locationscursor home – sets address counter to DDRAM 0display on/off control
cursor on/offdisplay character blink
cursor or display shiftfunction set
DL: data length interface (4 or 8 bits)N: number display linesF: character font
entry mode – what happens after character writeI/D: DDRAM incremented or decrementedS: shift display left or right
[1] Hitachi. HD44780U (LCD-II) Dot Matrix Liquid Crystal Display Controller/Driver Datasheet. www.datasheet4u.com/html/H/D/4/HD44780UA00FS_Hitachi.pdf.html
Set Function: 8 bite mode
Set Function: 4-bit mode
Function Set: #lines and font
Clear display
Set entry mode
Display Off
Character Generator ROM
Create your own fonts: 5x8 or 5x10 dot patterns
CGRAM can also be used as general purpose RAM
LCD Segment Displays
Lower tech, earlier design, cheapHere, each segment is made of 7 bars
Coding Segments
Each bar in a segment is labeled with a letterCreate map of bars to display each letter and number