Raspberry Pi 2 B, GPIO and resistors

[katangawise]

Hello,

I try to find which GPIO pins have internal resistors and values of those resistors.
In some sources wrote that only number of pins have internal resistors and others doesn't, in some sources wrote that all pins have resistors - it's confusing me...
Where can I found the real specification for Raspberry Pi 2 B to ensure that?
I want to connect number of buttons to Raspberry with wires of 15-20 meters length each and want to know if I should use an external resistors or can use an internals only.

Thanks a lot!

[joan]

All the GPIO have internal pull-ups to 3V3 and pull-downs to ground. They may be selected per GPIO by software (up, down, off). They are about 50k in value.

In addition pins 3 and 5 have hard-wired 1k8 pull-ups to 3V3 (so those pins can function as an I2C bus).

[katangawise]

Thanks for your replay!
So, you think it shouldn't be a problem to connect a buttons with a 20 meter wires to the Raspberry GPIOs?

[joan]

Thanks for your replay!
So, you think it shouldn't be a problem to connect a buttons with a 20 meter wires to the Raspberry GPIOs?

I'm sure 20 meters of wire will cause all sorts of problems with interference. I can't help with that aspect of your question.

[katangawise]

Thanks a lot!
Where can I found the spec that explain the internal resistors values?

[GTR2Fan]

Where can I found the spec that explain the internal resistors values?

A spec of that nature isn't going to tell you anything that joan hasn't told you already. You're probably going to need to add your own external pull up/pull down resistor(s) to avoid false triggering running a cable of that length.

I believe the current limit to be a maximum of 16mA per GPIO pin, but a maximum of 50mA in total spread between all GPIO pins, so you can calculate absolute minimum safe resistor values from that. Someone please correct me if I'm wrong.