3 Analog inputs with the K8055?

Kits PC Related Projects
1

Hi all

Does anyone know about having 3 analog inputs in the K8055 board. I need the A1 and A2 analog inputs but also a third one, even if not so dynamic. For instance a 4 or 5 bit conversion would be enough.
I thought of using a 4 bits analog digital converter with digital inputs connected on (board) I1 … I4 inputs, but it sounds strange to have such a conversion when using a PIC right behind !

Any suggestion ?

I could also use Zener diodes and transistors to make a 4-5 levels input threshold but I just hoped it would be useless…

2

One alternative may be to use an analog MUX (e.g. 74HC4053 or CD4053) in front of either of the existing analog inputs. Control the MUX with the digital outputs of the K8055.
Of course this solution is usable only if you measure DC or very low frequency signals and the input voltage is in the range 0V to 5V.
Pull-up resistors (10k… 47k) must be added to +5V from he digital outputs you are using to control the MUX.