Sharing same LCD between two microcontroller boards.

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savvej said:
resistance value should be much greater than input impedance of LCD pin,right?
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Hi,
The input resistance of the LCD logic is VERY high.
Its important that you consider the response time of the diode/resistor combination in order to keep the low going 'edges' of the signals going to the LCD within the required specification.

As the LCD pin low going signal is not an active pull down [ ie: direct connection to a PIC pin], it important that the passive pull down resistor is low enough to get a fast edge.
I would consider a pull down resistor of 4K7.
 
Adding diodes and 4k7 resistor did'nt work.

But why so?(Currently have solved problem by adding some dpdt switch to connect LCD to required board while operating.)
 
Last edited:
savvej said:
Adding diodes and 4k7 resistor did'nt work.

But why so?(Currently have solved problem by adding some dpdt switch to connect LCD to required board while operating.)
Click to expand...

Where did you add the resistors to the circuit,, post a quick sketch
 
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