Multiple Digital Read

Hello everyone,

I am using Arduino Mega to read 4 digital signals from another device (+5 Volts and 0).
However it seems that when 1 digital input get high all the remaining 3 they get high as well.
The ground is common and there is no problem with that.
By reverting the IO function of the other device and enabling INPUT_PULLUP mode, solves my problem but it is not very convenient for my whole hardware setup.

Thanks

..then they are driven high or floating. Maybe pulldown resistors can help you?

You need to explain your hardware in more detail than that if you want answers - what signals, what
other device, what speed, what kind of cable, how long a cable.