need more GPIO pin

popfaignant

Raspberry pi3 b+
Alim 5v 5A
Retropie 4.5.3

Hello everybody, I've made a bartel with joystick connected to the GPIO whith 12 buttons (⬆️⬇️⬅️➡️, start, select ,A, B, X, Y, L, R).
So my problem is that i want another button for the Hotkey. I'seen on this forum that the pin 3 and 5 aren't usable and i don't know where i can connect my hk.
I don't want to use select button for many reasons.
Do you have an answer ?

cyperghost

Search for MCP23017 or MCP23008 this expands your GPIOs with a I2C component and costs are very low.

popfaignant

@cyperghost thanks for your quick answer but on my gpio, just 12 pin are connected. It's to bad to have some pins free and can't connect my hk on these. I expected an other solution.

cyperghost

@popfaignant (Physical) Pin 3 and 5 are I2C communication pins. Imho opinion you can use them. Usually Pin5 and Pin6 are used for a cheap power button solution.

So Pin5 works for sure.
You can add

dtparam=i2c_arm=off
dtparam=i2s=off

to your config.txt - this will disable I2C and the Pin3 and 5 should be available as GPIO 2 and GPIO 3

popfaignant

@cyperghost oh great, I'll try !

popfaignant

@cyperghost where is the config.txt please ?

mitu

@popfaignant Put the SD card in your PC, the config.txt file should be on the BOOT partition. Or, if you're on the Raspbian system, in the /boot folder.

popfaignant

@mitu sorry, it doesn't work 😢
Thanks