Using GPIO34,35,36,39 for SPI MISO, or RX or else?

[zliudr]

I know that these pins have no pullup or pulldown and are input only. I wonder if it is a good idea to use one for SPI MISO, with or without an external pullup. I've not used these pins for anything since they are input-only and I had enough pins. Now I want to see what they can be used for, MISO, RX, reset to factory firmware or test buttons? Anyone done any of the above? I appreciate your input! Just don't want to mess up a good design because of these pins.

[ESP_Sprite]

Well, their only downside is that they're input-only, so if you can give them a purpose where they do not need to output anything or have pullups, you should be good. MISO sounds like a good signal for that (given the ESP32 is the master).

[zliudr]

Thanks ESP_Sprite! I really love the fact you can assign almost any pin to UART/SPI/I2C etc. This way once you design a platform, software/firmware defines functions, which is easy to implement, no need to go back to fab boards prototype again. I'm very glad I've decided to use the ESP ecosystem for my projects.