We don’t have PDAs anymore, but the SDIO spec remains. [ajlitt] dug up an SDIO driver for the ESP8089 chip, and found that you can liberate the ESP8266’s SPI bus by removing a flash memory ...

The SDIO interface supports one- or four-bit SDIO and SD interrupt with automatic card detection. The chip also handles bus-powered designs requiring less than 450 mW from a 3.3V supply.

Initialization, bus width and clock frequency settings, sending and receiving of commands as well as SDIO interrupt handling – all these functions can be applied to any SDIO device. Availability and ...

The SDIO Host and Device Controller IP Core is full-featured, easy-to-use, synthesizable design that is easily integrated into any SoC or FPGA development. It can also support a variety of host bus ...