Secure Digital Input/Output \(SDIO\) is a peripheral interface evolved from the Secure Digital \(SD\) memory card interface. The SDIO interface is compatible with SD memory cards and can be connected to devices that support the SDIO interface.
SDIO is widely used. Currently, many smartphones support SDIO, and many SDIO peripherals are developed for connections to smartphones. Common SDIO peripherals include WLAN, GPS, cameras, and Bluetooth.
The SDIO bus has two ends, named host and device. All communication starts when the host sends a command. The device can communicate with the host as long as it can parse the command of the host. An SDIO host can connect to multiple devices, as shown in the figure below.
- CLK signal: clock signal sent from the host to the device
