Digital Input on Raspberry Pi

[NJKirchner]

Attempting simple Digital Input on a Raspberry Pi 2 B, but only pin 7 is responsive to changes in grounding.

I'm using a simple jumper cable to take pin 39 ground and connect to the requisite digital pin (40, 11, 12, all the same).

all images I've caught online seem to indicate that simply grounding the DIO line will control it.

If there needs to be a more elaborate pull up/down circuit to use the other lines, that's fine, I'm just not finding it.

~,~

Norm 

[jorgemondadori]

Hey NJKirchner

just tested and it is working fine.

i got gnd for my circuit from pin 39, 3.3 from pin 1

pulled up GPIO (7, 38 and 40 for testing) from 3.3V line of my protoboard

then used the unconnected jumper in photo for grounding the pins.

LV professional 2020 with makerhub toolkit installed. RPI 3. 

[NJKirchner · Accepted solution]

Jorge,

Thanks for the reply.
I confirmed as well that a pulling circuit is necessary to properly commutate the DIO lines. Looks like pin 7 is a special snowflake that doesn't require it. 

For posterity, this should help anyone else

[rolfk]

All GPIO pins on the Raspberry Pi can have a configurable internal pull-up or pull-down resistor around 60k Ohm. However the current Linx driver does not support controlling this aspect of the GPIO pins. And it is anyhow not recommended to use them, you don't see them, and they can be disabled by any software on the Raspberry Pi at anytime and then cause problems. With an external pull-up or pull-down resistor as needed, you know that there is a resistor and how it is connected.

The exception are GPIO 2 und GPIO 3 (pin 3 and 5) which are used for the I2C interface and always have a relatively low impedance pull-up connector of around 1.8k Ohm on board wired to it.