PIC Inputs

[EmeraldW]

I need to monitor several pins that are going to be used as switches or triggers and I had a question on how to connect them. I was told to pull the pins low with a resistor and then connect the triggers to +5 when the trigger is set. If I connect it this way, wouldn't pulling the first pin high pull the rest high?

**broken link removed**

 

[Ian Rogers]

It depends on your circuit... I always pull the pins high with 470 ohm resistors, the switch the pins to ground (active low) then test a NOT condition ie if NOT RA0 then ....
Its up to you how you wish to read them..

 

[DerStrom8]

Not necessarily. Notice that your switch is connected directly to RA0/AN0, but there are two resistors between your switch and RA1/AN1. Depending on the values of the resistors, it should be enough resistance to keep the other pins in the low state, even when the switch is connected.

Der Strom

 

[Pommie]

A useful feature of Port B of the 16F628 is the internal weak pullups (WPUs). You enable them by clearing bit 7 of the OPTION register. With the WPUs enabled you only need external switches to ground.

Note also, if you stay with port A then you need to disable the comparators (CMCON=7).

Mike.

 

[Ian Rogers]

deleted post.

 

[Nigel Goodwin]

I need to monitor several pins that are going to be used as switches or triggers and I had a question on how to connect them. I was told to pull the pins low with a resistor and then connect the triggers to +5 when the trigger is set. If I connect it this way, wouldn't pulling the first pin high pull the rest high?

No, because the junction of the resistors is 'grounded' (connected to Vss).

 

[EmeraldW]

Thank you everyone.