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3.2" TFT interfacing with LPC2138

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vaibhavpawar

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I am using 3.2" TFT LCD using 16 bit parallel interface. But, due to unavailability of I/O pins I am multiplexing it using 3 state buffer and using only 8 pins to drive LCD's 16 data pins ( U2 and U5 in the image, SN74HCT245 both ). Header20x2 is TFT LCD header ( attached datasheet for LCD ).

tft.png

D0-D15 are LCD pins. Data0-Data7 are controller pins (LPC2138)

Data0-Data7 will be assigned to D0-D7 initially through U2 and U5 will be disabled ( U2 On,U5 off )

Data0-Data7 will be assigned to D8-D15 later through U5 and U2 will be disabled ( U5 On,U2 off )

Is these right approach to drive 16 bit LCD using 8 bit I/O pins.?

Link for datasheet download: https://drive.google.com/file/d/0B2_rhDNAxM4sTG5sVFVtbDhUSXM/view
 

KlausST

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Hi,

245 is a bidirectional buffer, but most likely you need a latch or a d-ff, at least in direction to lcd.

For better assistance we (and you) need a timing diagram.

Klaus
 

pjmelect

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As stated in the previous post you should use a latch instead of the 245.
The point of a 16 bit interface is for speed, would using a latch be any faster than writing 8 bits at a time without the latches? I don't think so!!
A trick that I used is to connect 10K resistors between the data lines ie 10k between D0 and D8 10K between D1 and D9 etc. This enables you to use 16bit mode if you are writing black (such as clearing the screen) or white (writing text). This can speed up the writing for black and white by two or three times.
 

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