I am currently designing a small PCB using SKRNPAE010 tactile switch - which has a DPST-NO circuit. I am looking to hook the switch up to a small computer such as a Raspberry Pi via GPIO pins. I have seen that it recommended to have pull-up resistors for switches connected to microcontrollers, etc. to stabilize the signal. I made the follow circuit, which I as far as I know is correct. VCC on pins 1 & 3 will be connected to the Pi's 3.3 Power Pin, while S1-1 and S1-2 will be connected to GPIO pins on the Pi. Likewise, pins 2 & 4 are grounded.

Could a get a sanity check for this circuit? Thank you!

 

Why do you need two inputs? Is it a safety requirement?

 

This is for a camera - I need to detect half presses (focusing the camera) and full presses (to take the picture.)

 

This is for a camera - I need to detect half presses (focusing the camera) and full presses (to take the picture.)

OK, that makes sense (I should have read the switch spec's first), 1st 0.78N, 2nd 2.45N. Your circuit looks fine but there will be contact bouncing. I assume the software will handle that to reliably detect the half and full presses.

 

No worries! But yep - I do plan on debouncing via software.

 

Your circuit looks fine

Because of the link between pins 2 and 3 of the switch, S1-2 is permanently grounded.

 

Because of the link between pins 2 and 3 of the switch, S1-2 is permanently grounded.

As far as I know, this should be the intended behavior:

• When unpressed, S1-1 and S1-1 will be HIGH because of the pull up resistor
• When half pressed, S1-1 will be LOW and S1-2 HIGH
• When fully pressed, S1-1 * and * S1-2 will be LOW

Would this circuit not give that behavior? If so - what would need to be changed? This is the diagram from the datasheet:

 

what would need to be changed?

Swap the connections between pins 3 and 4.

 

Because of the link between pins 2 and 3 of the switch, S1-2 is permanently grounded.

Good catch. That's what happens when you look more at the gpio interface than the actual switch wiring. Getting old sucks.

 

Getting old sucks.

I am in my eighth decade!

 

I am in my eighth decade!

Writing this in my second decade!

Otherwise, this is correct?

 

looks good