Matrix user forums

Hi,

My project consist in replace 8 push buttons of my card by a PIC to simulate those push buttons and controlled it by RS232.
I use PORT B of my PIC and I just want to know if i need to use a "intermediate" circuit (like ULN2803 ie) to interface to my card or can i connect my PIC directly. (my card have 8 pull up 10K ohm resistor to 5 V)

thank for your help

MIKE

Hello Mike,

A PIC has more than enough current sinking capability to drive a 10k pull-up to 5v. So a ULN2803 would not give any advantage (unless the signal inversion is required).

We can not give advice on interfacing PIC circuits to boards we do not know. Some boards can have their control circuits referenced to unexpected voltages (including dangerous mains supply phases).

If you are sure that the 5v supply to the switches is references to a safe 0v, it should be o.k. to drive the switch inputs directly. If you are unsure, opto-isolators would probably represent a useful circuit addition.

Thanks a lot for you reply Sean,

I will try to test my circuit directly with the PIC.


MIKE