The caravel (not caravan) framework user_project_wrapper.v has access to the analog connection of the gpio, but only for 28 pins. Here’s the explanation in the rtl

// Analog (direct connection to GPIO pad---use with caution)
    // Note that analog I/O is not available on the 7 lowest-numbered
    // GPIO pads, and so the analog_io indexing is offset from the
    // GPIO indexing by 7 (also upper 2 GPIOs do not have analog_io).
    inout [`MPRJ_IO_PADS-10:0] analog_io,

So the

user_project_wrapper

signal

analog_io[0]

corresponds to gpio 7 (counting from 0). The expected configuration for the gpio’s with user analog signals is

GPIO_MODE_USER_STD_ANALOG

, but you may want to make sure that the corresponding

io_oeb[x]

signal is fixed high. For example, for

analog_io[0]

set

io_oeb[7]

to 1'b1.