savvej
Member
I have two microcontroller 8051(P89v51rd2) boards and have made an lcd board having two set of output pins available for each lcd pin.
LCD is given VCC,and Gnd separately. And the microcontroller boards have a separate power supply and power supply switch(with the grnds of each of the boards and the lcd unit connected together)
Two set of connector wires connect each of the pins rs,rw,en,d0-d7 to each of the two microcontroller ports.
The LCD is always powered on.
Now when I switch on one of the boards(say board1) while the other is powered off ,there is nothing displayed on the LCD.But if I now disconnect the LCD connector from board2(the other board) and then again restart board 1 ,it works perfectly fine.
Similarly if I switch on board 2 and remove LCD connector from board1,it too works fine.This implies that each of the unit works fine independently.
But when both connectors are connected with only one of them switched on it doesn't work.
So what I think is that sharing of LCD pins to the other microcontroller affects the voltage levels at the microcontroller LCD PORT ouyput even though the other is switched off (i.e. its pin40(VCC) is disconnected from power supply).What I have proposed is that can connecting low voltage drop diodes(like 1n4148) and the LCD port pins of microcontroller solve this problem by keeping the voltage levels fixed the individual ports?
Please comment and suggest some solutions for the same.
If you want any info regarding voltage levels at the pins or any other info please do ask.
LCD is given VCC,and Gnd separately. And the microcontroller boards have a separate power supply and power supply switch(with the grnds of each of the boards and the lcd unit connected together)
Two set of connector wires connect each of the pins rs,rw,en,d0-d7 to each of the two microcontroller ports.
The LCD is always powered on.
Now when I switch on one of the boards(say board1) while the other is powered off ,there is nothing displayed on the LCD.But if I now disconnect the LCD connector from board2(the other board) and then again restart board 1 ,it works perfectly fine.
Similarly if I switch on board 2 and remove LCD connector from board1,it too works fine.This implies that each of the unit works fine independently.
But when both connectors are connected with only one of them switched on it doesn't work.
So what I think is that sharing of LCD pins to the other microcontroller affects the voltage levels at the microcontroller LCD PORT ouyput even though the other is switched off (i.e. its pin40(VCC) is disconnected from power supply).What I have proposed is that can connecting low voltage drop diodes(like 1n4148) and the LCD port pins of microcontroller solve this problem by keeping the voltage levels fixed the individual ports?
Please comment and suggest some solutions for the same.
If you want any info regarding voltage levels at the pins or any other info please do ask.
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