ESP32 Forum

Hi,

I am reading thru the Esp32-p4_technical_reference_manual_en and it very unclear even for a simple query. For instance, I see some example code used GPIO14 for SDIO function, however in the documentation there is no alternate function for GPIO14! So how in the world it works?

If by 'alternate function', you mean the IOMUX setting of that pin, you'd be correct. SD-card signals are mappable either using the IOMUX functionality of GPIO37-48, or to any GPIO (that is not otherwise used) using the GPIO matrix; the example uses the latter. If you're used to other microcontrollers, it's good to keep in mind that IO allocation isn't nearly as restricted on the ESP32; with a few exceptions (e.g. analog functions, peripherals that need a phy for IO like USB or MIPI and some high-speed periperals like Ethernet) you can allocate any IO function to any GPIO pin.