# Why does this Pico circuit use so many resistors?

I've just started working through the Freenove ultimate starter kit for the Pi Pico, and I'm having trouble understanding why it has so many resistors in this circuit.

I'm following the tutorial document at https://github.com/Freenove/Freenove_Ultimate_Starter_Kit_for_Raspberry_Pi_Pico/blob/master/Python/Python_Tutorial.pdf and have made it to project 2.1. The relevant circuit diagram is attached.

I understand it uses a 220ohm resistor to prevent the LED burning out.

It also uses 2 10k resistors connected to the button - these are the ones that I don't understand. I'm trying to clarify a number of things:

• Am I correct in thinking that 2 10k resistors in series are the equivalent of a single 20k resistor?
• Is this done so that we're not passing too much current to the GP13 pin?

I'm having trouble finding an answer as to what the acceptable inputs for the GPIO pins are - the closest I've found is What are the min/max voltage/current values the gpio pins can handle? which recommends no more than 0.5mA. But that's an old post, and not specifically about the Pico.

• Assuming the GPIO pin could take the full 3.3V @ whatever Amps, would I need either of these resistors?
• Could I remove safely remove just R2?

This is my first introduction to electronics, so I'm very much in the camp of not even knowing what topics I need to understand. Any advice would be greatly appreciated.

• You picked a rather poor example. "Is this done so that we're not passing too much current to the GP13 pin?" No CMOS; is very high impedance so no current will flow into an INPUT - it is there in case it is configured as OUTPUT (unnecessary IMO). "Could I remove safely remove just R2" No you NEED a pullup (although IMO 10k is too high) Jul 28 at 10:16
• Unfortunately anyone can post a "tutorial" on the internet. WHY anyone follows them (and how they find them) is a mystery. Raspberry Pi Ltd. has plenty of good documentation. Jul 28 at 10:22
• 3 is "so many" ... OK Jul 28 at 12:06
• the resistors have labels ... please use them when referring to the resistors ... R2 and R3 are not in series per se ... you cannot replace them with one resistor and retain the circuit topology Jul 29 at 0:17
• @Milliways I bought amazon.co.uk/dp/B09H2TFRN2 which is a pretty cool little kit, with a bunch of stuff nice and cheap. As you've found though, the included tutorials aren't great. Jul 29 at 12:49