The latest development version of this page may be more current than this released 2.3-beta.2 version.

SDIO Slave

Introduction

The SDIO Slave module provides functionality for communicating with a host as an SDIO slave device.

  • SDIO Slave: An interface for embedded systems that allows devices to communicate with a host via the Secure Digital Input Output (SDIO) interface as a slave device

  • Zero Copy: Data transfer uses zero copy method to reduce memory copy overhead and improve transfer efficiency

Feature List

  • Supports Function 0 (configuration and control) and Function 1 (data transfer)

  • Supports CIS register read/write

  • Supports synchronous and asynchronous data transfer

  • Supports command reception

  • Supports event callback mechanism

Feature Overview

SDIO Slave main features include:

  • CIS Register Access: - Supports reading and writing CIS registers for Function 0 and Function 1 - Each Function supports up to 128 bytes of CIS data

  • Data Transfer: - Synchronous transfer: Blocks waiting for transfer completion - Asynchronous transfer: Returns immediately, notifies completion via callback - Maximum transfer buffer is 8192 bytes (TX) and 4096 bytes (RX) - Uses zero copy method, application layer must ensure data remains valid until transfer completes

  • Command Processing: - Supports receiving commands from host - Command buffer size is 256 bytes

  • Event Callbacks: - Supports registering callback functions for data send/receive completion events - Supports command send/receive completion event notifications

Hardware Configuration

Configure the following parameters via Device Tree (DT):

  • Pin multiplexing configuration

  • Interrupt configuration

Main Functions

CIS Register Configuration

Prerequisites:

  • SDIO Slave device is initialized

Related APIs:

  • Call wm_drv_sdio_slave_read_cis_reg to read CIS register

  • Call wm_drv_sdio_slave_write_cis_reg to write CIS register

Parameters:

  • func: Function number (0-1)

  • pos: Register address (0-123)

  • val: Register value (32-bit)

Results:

  • Returns register value on successful read

  • Returns WM_ERR_SUCCESS on successful write

  • Returns corresponding error code on failure

Notes

  • Each Function supports up to 128 bytes of CIS data

  • CIS registers should be configured based on SDIO card usage, refer to cis.c file under examples/peripheral/sdio_slave

  • CIS register configuration should be completed during initialization, modification during runtime is not recommended

  • CIS data contains important parameters like manufacturer info, function description, maximum clock frequency

  • Incorrect CIS configuration may cause host to fail recognizing slave device

Data Transfer

Prerequisites:

  • SDIO Slave device is initialized

  • Event callback function is registered

Related APIs:

  • Call wm_drv_sdio_slave_init to initialize device

  • Call wm_drv_sdio_slave_tx_data_sync for synchronous data sending

  • Call wm_drv_sdio_slave_tx_data_async for asynchronous data sending

  • Call wm_drv_sdio_slave_rx_data to receive data

Results:

  • Returns WM_ERR_SUCCESS on success

  • Returns corresponding error code on failure

Command Processing

Prerequisites:

  • SDIO Slave device is initialized

  • Event callback function is registered

Related APIs:

  • Call wm_drv_sdio_slave_rx_cmd to receive command

Results:

  • Returns WM_ERR_SUCCESS and notifies via callback on success

  • Returns corresponding error code on failure

Notes

  • For data transfer, buffer must be allocated using wm_heap_caps_alloc() with WM_HEAP_CAP_SHARED flag

  • Maximum send data length is 8192 bytes

  • Maximum receive data length is 4096 bytes

  • Command receive buffer size is 256 bytes

  • Callback functions execute in interrupt context, should be kept brief

  • Due to zero copy data transfer, application layer must ensure:

    • Send data is not freed or modified before transfer completes

    • Received data is processed promptly

Application Example

For basic SDIO Slave usage example, refer to examples/peripheral/sdio_slave

API Reference

API Reference