On the ESP8266 NodeMCU I have GPIO2 , GPIO3 , GPIO1 , GPIO9 free but when I assign them to a button they do not work. I assume it is because those pins have other function behind them. When I look at the schematic I found that they are TXD1, RXD0, TXD0, and SSD2. Is there a way to still use these pins as inputs?
If not, can I use an Arduino Uno for my inputs and send signals from there to the analog pin to my ESP8266 NodeMCU for the connection to the MQTT server?
For the record all my other pins are used so I can't use any other input pin than these 4.