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MSP430F67791A: Implementing LCD and Push Buttons to same pin of micro controller

PRASIDDHNATH YADAV
Prodigy 50 points
Part Number: MSP430F67791A


Hi,

I am using a IC 74HCT245 Octal bus transceiver 3-state to interface with MSP430F67791A controller to implement a logic in which it should give output to LCD (RS,EN,D4,D5,D6,D7 pins)and in one end I have connected 6 Push Buttons. 

I am using LCD in 4 Bit mode its working properly.

However, I am not able to detect the Push Buttons State as every time when any of the button is press it shows garbage value in LCD display.

IC74HCT245  Pin Connections:

Pin 1 and 20 is connected to 5V

Pin 19 and 10 is connected to GND

Pins(2 to 9) is A side of IC which is connected to Push Button also this pin is connected to the controller pins(Port 5).

Pins(11 to 18) is B Side of IC  which is connected to LCD.

Any Hints would be of great help.

Regards,

  • 0
    TI__Genius 10270 points

    Hi,

    I found that pin19 is nOE, which enable the output. High = all ports in high impedance mode, Low = all ports active. So If you want the buttons to not affect the LCD, you should control pin19 to make all ports in high impedance mode.

    By the way, pin1 is the DIR, which determines the direction of the signal. High = A to B, Low = B to A. Since pin1 is connected to 5V, the signal from A side is always transferred to B side.

    Thanks,

    Yuhao

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