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Low-Cost LCD Controller (2)

the hardware

Low-Cost LCD Controller (2)
In this month’s instalment we apply the theoretical knowledge obtained from part 1 to make an 8051 microcontroller drive a matrix display salvaged from a computer game. Because the LCD requires relatively high data speeds, a hardware trick is used to keep the controller software overhead within reason.To prevent flicker, matrix LCDs must be refreshed at frame rates greater than 50 Hz. The concept of the low-cost LCD controller is based on an 8051 microcontroller that creates and keeps an image in its external RAM and then reads the image at the required frame rate. The image databytes read from the external RAM are sent to the LCD display drivers. Clearly, performance optimisation is a major consideration if we are to achieve the required refresh rate and still preserve controller time for other tasks.
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Gerber file

CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor Members can exclusively download these files for free as part of their Membership. Gerber files allow a PCB to be produced on an appropriate device available locally, or through an online PCB manufacturing service. Elektor recommends its business partner Eurocircuits as the company of choice for its own prototypes and volume production in selected cases.

Resistors:
R1,R2 = 10k?
P1= 10k? preset
Capacitors:
C1,C2 = 10pF
C3,C4,C9-C13 = 100nF
C5-C8 = 10µF 16V radial
Semiconductors:
D1 = BAT85
D2 =12V 400mW zener diode
IC1 = 74HC157
IC2 = 74HC74
IC3 = 74HC04
IC4 = 74HC27
IC5 = 74HC123
IC6,IC7 = MAX1044/CP
Miscellaneous:
JP1 = 3-way header with jumper
K1 = 12-way pinheader
K2 = 34-way boxheader
K3 = 3-way pinheader
PCB, order code 020114-1, see Readers Services page
Disk, contains all project software, order code 020114-11 or Free Download
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