Crate sdmmc_protocol 

no_std SD/MMC protocol building blocks for embedded systems.

This crate provides protocol-level types and driver skeletons for SD, MMC and SDIO cards. It is transport-agnostic at the trait level and brings its own SPI-mode driver plus an SDIO host-controller abstraction.

What you get

• cmd::Command / cmd::DataDirection: SD/MMC command opcodes, argument encoding and per-command data direction.
• response::Response and friends (response::CidResponse, response::CsdResponse, response::SwitchStatus, …): typed parsers for the response formats defined in the SD spec.
• error::Error: a single error enum the drivers and parsers return.
• spi (feature spi, on by default): a spi::SpiTransport trait plus the spi::SpiSdmmc driver for SPI-mode SD cards. Includes a thin spi::SpiDeviceWrapper adapter for embedded-hal 1.0 SpiDevice<u8> implementations.
• [sdio] (feature sdio): a [sdio::SdioHost] trait that abstracts a host controller and the [sdio::SdioSdmmc] driver that drives it through card initialization, block I/O and bus-speed selection.

Cargo features

Feature	Default	Purpose
spi	yes	Enables spi::SpiTransport and spi::SpiSdmmc.
sdio	no	Enables the host trait and submit/poll data-command contract.

Diagnostic output goes through the log crate; configure a logger in your application to capture it.

Example

use embedded_hal::delay::DelayNs;
use sdmmc_protocol::{
    Error,
    spi::{SpiSdmmc, SpiTransport},
};

struct MySpi;

impl SpiTransport for MySpi {
    fn transfer_byte(&mut self, byte: u8) -> Result<u8, Error> {
    }
}

fn boot<D: DelayNs>(spi: MySpi, delay: D) -> Result<(), Error> {
    let mut card = SpiSdmmc::new(spi, delay);
    let _info = card.init()?;
    let mut block = [0u8; 512];
    card.read_block(0, &mut block)?;
    Ok(())
}

Maturity

The SPI path has protocol-level unit tests and basic block read/write support. The SDIO path has been validated end-to-end against several host controller / SoC combinations through the dedicated host backends in this workspace:

Host crate	SoC / controller	Mode	Status
sdhci-host	RK3568 (dwcmshc)	eMMC HS@52, FIFO/DMA	OK
sdhci-host	RK3588 (dwcmshc)	eMMC HS@52, FIFO/DMA	OK
dwmmc-host	RK3568 SD (dw_mshc)	SD HS, DMA	OK
phytium-mci-host	Phytium MCI	SD HS, DMA	OK

UHS-I / HS200 / HS400 paths exist in the state machine but have not yet been signed off on a real card + IO regulator combination. See drivers/blk/sdmmc-protocol/docs/REVIEW.md for the remaining roadmap.

MSRV

Rust 1.85 (the first stable to ship edition 2024).

Re-exports

pub use block::BlockBufferConfig;

pub use block::BlockPoll;

pub use block::BlockRequestId;

pub use block::BlockTransferDirection;

pub use block::BlockTransferMode;

pub use block::BlockTransferState;

pub use block::CommandPoll;

pub use block::CommandResponsePoll;

pub use block::DataCommandDirection;

pub use block::DataCommandPoll;

pub use block::DataCommandState;

pub use block::OperationPoll;

pub use cmd::Command;

pub use cmd::DataDirection;

pub use error::Error;

pub use error::ErrorContext;

pub use error::Phase;

pub use response::CidResponse;

pub use response::CsdResponse;

pub use response::Response;

pub use response::SwitchStatus;

Modules

block

Block request state shared by SD/MMC host controller backends.

cmd

error

Error and diagnostic context types returned by drivers and parsers.

ext_csd

Extended CSD (EXT_CSD) register parsing for eMMC / MMC cards.

response

spi

SPI mode transport layer for SD/MMC cards