16f877a ports low high state problem

[infrared]

I have a 4x2 bit BCD outputs from a machine to connect as inputs to PORTD of PIC 16f877a.

My problem is that the BCD outputs of the machine is .38 volts for low state and .90 volts for high state and because the PORT of PIC is TTL it cannot understood the high and low states.

What can i do?
Is it possible to define the high and low volts of the PIC PORTD or there is another
solution ?
I am trying to create i pinball MPU tester but i dont know what to do with this
problem.

Any help please ?

 

[matbob]

Hi infrared,

Since your high input is greater than 0.7V, you can try giving the input to a transistor wired as a switch. The output would be inverted in that case. Try the ckt given.

 

[infrared]

matbob thank you very much i will try it !!!!!

Added after 3 hours 11 minutes:

matbob is it possible to use a transistor but with no inverted output ?

 

[matbob]

Hi infrared,

You may use two such stages so that the input get inverted two times which will give you a normal output. But if you are using a microcontroller it is not required because you can do the inversion in the software very easily.