SD/SDIO/MMC Driver
Overview
The SD/SDIO/MMC driver currently supports SD memory, SDIO cards, and eMMC chips. This is a protocol level driver built on top of SDMMC and SD SPI host drivers.
SDMMC and SD SPI host drivers (driver/include/driver/sdmmc_host.h and driver/include/driver/sdspi_host.h) provide API functions for:
Sending commands to slave devices
Sending and receiving data
Handling error conditions within the bus
For functions used to initialize and configure:
SDMMC host, see SDMMC Host API
SD SPI host, see SD SPI Host API
The SDMMC protocol layer described in this document handles the specifics of the SD protocol, such as the card initialization and data transfer commands.
The protocol layer works with the host via the sdmmc_host_t
structure. This structure contains pointers to various functions of the host.
Application Example
An example which combines the SDMMC driver with the FATFS library is provided in the storage/sd_card directory of ESP-IDF examples. This example initializes the card, then writes and reads data from it using POSIX and C library APIs. See README.md file in the example directory for more information.
Combo (memory + IO) cards
The driver does not support SD combo cards. Combo cards are treated as IO cards.
Thread safety
Most applications need to use the protocol layer only in one task. For this reason, the protocol layer does not implement any kind of locking on the sdmmc_card_t
structure, or when accessing SDMMC or SD SPI host drivers. Such locking is usually implemented on a higher layer, e.g., in the filesystem driver.
Protocol layer API
The protocol layer is given the sdmmc_host_t
structure. This structure describes the SD/MMC host driver, lists its capabilities, and provides pointers to functions of the driver. The protocol layer stores card-specific information in the sdmmc_card_t
structure. When sending commands to the SD/MMC host driver, the protocol layer uses the sdmmc_command_t
structure to describe the command, arguments, expected return values, and data to transfer if there is any.
Using API with SD memory cards
To initialize the host, call the host driver functions, e.g.,
sdmmc_host_init()
,sdmmc_host_init_slot()
.To initialize the card, call
sdmmc_card_init()
and pass to it the parametershost
- the host driver information, andcard
- a pointer to the structuresdmmc_card_t
which will be filled with information about the card when the function completes.To read and write sectors of the card, use
sdmmc_read_sectors()
andsdmmc_write_sectors()
respectively and pass to it the parametercard
- a pointer to the card information structure.If the card is not used anymore, call the host driver function - e.g.,
sdmmc_host_deinit()
- to disable the host peripheral and free the resources allocated by the driver.
Using API with eMMC chips
From the protocol layer’s perspective, eMMC memory chips behave exactly like SD memory cards. Even though eMMCs are chips and do not have a card form factor, the terminology for SD cards can still be applied to eMMC due to the similarity of the protocol (sdmmc_card_t, sdmmc_card_init). Note that eMMC chips cannot be used over SPI, which makes them incompatible with the SD SPI host driver.
To initialize eMMC memory and perform read/write operations, follow the steps listed for SD cards in the previous section.
Using API with SDIO cards
Initialization and the probing process are the same as with SD memory cards. The only difference is in data transfer commands in SDIO mode.
During the card initialization and probing, performed with sdmmc_card_init()
, the driver only configures the following registers of the IO card:
The IO portion of the card is reset by setting RES bit in the I/O Abort (0x06) register.
If 4-line mode is enabled in host and slot configuration, the driver attempts to set the Bus width field in the Bus Interface Control (0x07) register. If setting the filed is successful, which means that the slave supports 4-line mode, the host is also switched to 4-line mode.
If high-speed mode is enabled in the host configuration, the SHS bit is set in the High Speed (0x13) register.
In particular, the driver does not set any bits in (1) I/O Enable and Int Enable registers, (2) I/O block sizes, etc. Applications can set them by calling sdmmc_io_write_byte()
.
For card configuration and data transfer, choose the pair of functions relevant to your case from the table below.
Action |
Read Function |
Write Function |
---|---|---|
Read and write a single byte using IO_RW_DIRECT (CMD52) |
||
Read and write multiple bytes using IO_RW_EXTENDED (CMD53) in byte mode |
||
Read and write blocks of data using IO_RW_EXTENDED (CMD53) in block mode |
SDIO interrupts can be enabled by the application using the function sdmmc_io_enable_int()
. When using SDIO in 1-line mode, the D1 line also needs to be connected to use SDIO interrupts.
If you want the application to wait until the SDIO interrupt occurs, use sdmmc_io_wait_int()
.
There is a component ESSL (ESP Serial Slave Link) to use if you are communicating with an ESP32 SDIO slave. See ESP Serial Slave Link and example peripherals/sdio/host.
API Reference
Header File
Functions
-
esp_err_t sdmmc_card_init(const sdmmc_host_t *host, sdmmc_card_t *out_card)
Probe and initialize SD/MMC card using given host
Note
Only SD cards (SDSC and SDHC/SDXC) are supported now. Support for MMC/eMMC cards will be added later.
- Parameters
host – pointer to structure defining host controller
out_card – pointer to structure which will receive information about the card when the function completes
- Returns
ESP_OK on success
One of the error codes from SDMMC host controller
-
void sdmmc_card_print_info(FILE *stream, const sdmmc_card_t *card)
Print information about the card to a stream.
- Parameters
stream – stream obtained using fopen or fdopen
card – card information structure initialized using sdmmc_card_init
-
esp_err_t sdmmc_get_status(sdmmc_card_t *card)
Get status of SD/MMC card
- Parameters
card – pointer to card information structure previously initialized using sdmmc_card_init
- Returns
ESP_OK on success
One of the error codes from SDMMC host controller
-
esp_err_t sdmmc_write_sectors(sdmmc_card_t *card, const void *src, size_t start_sector, size_t sector_count)
Write given number of sectors to SD/MMC card
- Parameters
card – pointer to card information structure previously initialized using sdmmc_card_init
src – pointer to data buffer to read data from; data size must be equal to sector_count * card->csd.sector_size
start_sector – sector where to start writing
sector_count – number of sectors to write
- Returns
ESP_OK on success
One of the error codes from SDMMC host controller
-
esp_err_t sdmmc_read_sectors(sdmmc_card_t *card, void *dst, size_t start_sector, size_t sector_count)
Read given number of sectors from the SD/MMC card
- Parameters
card – pointer to card information structure previously initialized using sdmmc_card_init
dst – pointer to data buffer to write into; buffer size must be at least sector_count * card->csd.sector_size
start_sector – sector where to start reading
sector_count – number of sectors to read
- Returns
ESP_OK on success
One of the error codes from SDMMC host controller
-
esp_err_t sdmmc_erase_sectors(sdmmc_card_t *card, size_t start_sector, size_t sector_count, sdmmc_erase_arg_t arg)
Erase given number of sectors from the SD/MMC card
Note
When sdmmc_erase_sectors used with cards in SDSPI mode, it was observed that card requires re-init after erase operation.
- Parameters
card – pointer to card information structure previously initialized using sdmmc_card_init
start_sector – sector where to start erase
sector_count – number of sectors to erase
arg – erase command (CMD38) argument
- Returns
ESP_OK on success
One of the error codes from SDMMC host controller
-
esp_err_t sdmmc_can_discard(sdmmc_card_t *card)
Check if SD/MMC card supports discard
- Parameters
card – pointer to card information structure previously initialized using sdmmc_card_init
- Returns
ESP_OK if supported by the card/device
ESP_FAIL if not supported by the card/device
-
esp_err_t sdmmc_can_trim(sdmmc_card_t *card)
Check if SD/MMC card supports trim
- Parameters
card – pointer to card information structure previously initialized using sdmmc_card_init
- Returns
ESP_OK if supported by the card/device
ESP_FAIL if not supported by the card/device
-
esp_err_t sdmmc_mmc_can_sanitize(sdmmc_card_t *card)
Check if SD/MMC card supports sanitize
- Parameters
card – pointer to card information structure previously initialized using sdmmc_card_init
- Returns
ESP_OK if supported by the card/device
ESP_FAIL if not supported by the card/device
-
esp_err_t sdmmc_mmc_sanitize(sdmmc_card_t *card, uint32_t timeout_ms)
Sanitize the data that was unmapped by a Discard command
Note
Discard command has to precede sanitize operation. To discard, use MMC_DICARD_ARG with sdmmc_erase_sectors argument
- Parameters
card – pointer to card information structure previously initialized using sdmmc_card_init
timeout_ms – timeout value in milliseconds required to sanitize the selected range of sectors.
- Returns
ESP_OK on success
One of the error codes from SDMMC host controller
-
esp_err_t sdmmc_full_erase(sdmmc_card_t *card)
Erase complete SD/MMC card
- Parameters
card – pointer to card information structure previously initialized using sdmmc_card_init
- Returns
ESP_OK on success
One of the error codes from SDMMC host controller
-
esp_err_t sdmmc_io_read_byte(sdmmc_card_t *card, uint32_t function, uint32_t reg, uint8_t *out_byte)
Read one byte from an SDIO card using IO_RW_DIRECT (CMD52)
- Parameters
card – pointer to card information structure previously initialized using sdmmc_card_init
function – IO function number
reg – byte address within IO function
out_byte – [out] output, receives the value read from the card
- Returns
ESP_OK on success
One of the error codes from SDMMC host controller
-
esp_err_t sdmmc_io_write_byte(sdmmc_card_t *card, uint32_t function, uint32_t reg, uint8_t in_byte, uint8_t *out_byte)
Write one byte to an SDIO card using IO_RW_DIRECT (CMD52)
- Parameters
card – pointer to card information structure previously initialized using sdmmc_card_init
function – IO function number
reg – byte address within IO function
in_byte – value to be written
out_byte – [out] if not NULL, receives new byte value read from the card (read-after-write).
- Returns
ESP_OK on success
One of the error codes from SDMMC host controller
-
esp_err_t sdmmc_io_read_bytes(sdmmc_card_t *card, uint32_t function, uint32_t addr, void *dst, size_t size)
Read multiple bytes from an SDIO card using IO_RW_EXTENDED (CMD53)
This function performs read operation using CMD53 in byte mode. For block mode, see sdmmc_io_read_blocks.
- Parameters
card – pointer to card information structure previously initialized using sdmmc_card_init
function – IO function number
addr – byte address within IO function where reading starts
dst – buffer which receives the data read from card
size – number of bytes to read
- Returns
ESP_OK on success
ESP_ERR_INVALID_SIZE if size exceeds 512 bytes
One of the error codes from SDMMC host controller
-
esp_err_t sdmmc_io_write_bytes(sdmmc_card_t *card, uint32_t function, uint32_t addr, const void *src, size_t size)
Write multiple bytes to an SDIO card using IO_RW_EXTENDED (CMD53)
This function performs write operation using CMD53 in byte mode. For block mode, see sdmmc_io_write_blocks.
- Parameters
card – pointer to card information structure previously initialized using sdmmc_card_init
function – IO function number
addr – byte address within IO function where writing starts
src – data to be written
size – number of bytes to write
- Returns
ESP_OK on success
ESP_ERR_INVALID_SIZE if size exceeds 512 bytes
One of the error codes from SDMMC host controller
-
esp_err_t sdmmc_io_read_blocks(sdmmc_card_t *card, uint32_t function, uint32_t addr, void *dst, size_t size)
Read blocks of data from an SDIO card using IO_RW_EXTENDED (CMD53)
This function performs read operation using CMD53 in block mode. For byte mode, see sdmmc_io_read_bytes.
- Parameters
card – pointer to card information structure previously initialized using sdmmc_card_init
function – IO function number
addr – byte address within IO function where writing starts
dst – buffer which receives the data read from card
size – number of bytes to read, must be divisible by the card block size.
- Returns
ESP_OK on success
ESP_ERR_INVALID_SIZE if size is not divisible by 512 bytes
One of the error codes from SDMMC host controller
-
esp_err_t sdmmc_io_write_blocks(sdmmc_card_t *card, uint32_t function, uint32_t addr, const void *src, size_t size)
Write blocks of data to an SDIO card using IO_RW_EXTENDED (CMD53)
This function performs write operation using CMD53 in block mode. For byte mode, see sdmmc_io_write_bytes.
- Parameters
card – pointer to card information structure previously initialized using sdmmc_card_init
function – IO function number
addr – byte address within IO function where writing starts
src – data to be written
size – number of bytes to read, must be divisible by the card block size.
- Returns
ESP_OK on success
ESP_ERR_INVALID_SIZE if size is not divisible by 512 bytes
One of the error codes from SDMMC host controller
-
esp_err_t sdmmc_io_enable_int(sdmmc_card_t *card)
Enable SDIO interrupt in the SDMMC host
- Parameters
card – pointer to card information structure previously initialized using sdmmc_card_init
- Returns
ESP_OK on success
ESP_ERR_NOT_SUPPORTED if the host controller does not support IO interrupts
-
esp_err_t sdmmc_io_wait_int(sdmmc_card_t *card, TickType_t timeout_ticks)
Block until an SDIO interrupt is received
Slave uses D1 line to signal interrupt condition to the host. This function can be used to wait for the interrupt.
- Parameters
card – pointer to card information structure previously initialized using sdmmc_card_init
timeout_ticks – time to wait for the interrupt, in RTOS ticks
- Returns
ESP_OK if the interrupt is received
ESP_ERR_NOT_SUPPORTED if the host controller does not support IO interrupts
ESP_ERR_TIMEOUT if the interrupt does not happen in timeout_ticks
-
esp_err_t sdmmc_io_get_cis_data(sdmmc_card_t *card, uint8_t *out_buffer, size_t buffer_size, size_t *inout_cis_size)
Get the data of CIS region of an SDIO card.
You may provide a buffer not sufficient to store all the CIS data. In this case, this function stores as much data into your buffer as possible. Also, this function will try to get and return the size required for you.
- Parameters
card – pointer to card information structure previously initialized using sdmmc_card_init
out_buffer – Output buffer of the CIS data
buffer_size – Size of the buffer.
inout_cis_size – Mandatory, pointer to a size, input and output.
input: Limitation of maximum searching range, should be 0 or larger than buffer_size. The function searches for CIS_CODE_END until this range. Set to 0 to search infinitely.
output: The size required to store all the CIS data, if CIS_CODE_END is found.
- Returns
ESP_OK: on success
ESP_ERR_INVALID_RESPONSE: if the card does not (correctly) support CIS.
ESP_ERR_INVALID_SIZE: CIS_CODE_END found, but buffer_size is less than required size, which is stored in the inout_cis_size then.
ESP_ERR_NOT_FOUND: if the CIS_CODE_END not found. Increase input value of inout_cis_size or set it to 0, if you still want to search for the end; output value of inout_cis_size is invalid in this case.
and other error code return from sdmmc_io_read_bytes
-
esp_err_t sdmmc_io_print_cis_info(uint8_t *buffer, size_t buffer_size, FILE *fp)
Parse and print the CIS information of an SDIO card.
Note
Not all the CIS codes and all kinds of tuples are supported. If you see some unresolved code, you can add the parsing of these code in sdmmc_io.c and contribute to the IDF through the Github repository.
using sdmmc_card_init
- Parameters
buffer – Buffer to parse
buffer_size – Size of the buffer.
fp – File pointer to print to, set to NULL to print to stdout.
- Returns
ESP_OK: on success
ESP_ERR_NOT_SUPPORTED: if the value from the card is not supported to be parsed.
ESP_ERR_INVALID_SIZE: if the CIS size fields are not correct.
Header File
Structures
-
struct sdmmc_csd_t
Decoded values from SD card Card Specific Data register
-
struct sdmmc_cid_t
Decoded values from SD card Card IDentification register
-
struct sdmmc_scr_t
Decoded values from SD Configuration Register Note: When new member is added, update reserved bits accordingly
Public Members
-
uint32_t sd_spec
SD Physical layer specification version, reported by card
-
uint32_t erase_mem_state
data state on card after erase whether 0 or 1 (card vendor dependent)
-
uint32_t bus_width
bus widths supported by card: BIT(0) — 1-bit bus, BIT(2) — 4-bit bus
-
uint32_t reserved
reserved for future expansion
-
uint32_t rsvd_mnf
reserved for manufacturer usage
-
uint32_t sd_spec
-
struct sdmmc_ssr_t
Decoded values from SD Status Register Note: When new member is added, update reserved bits accordingly
Public Members
-
uint32_t alloc_unit_kb
Allocation unit of the card, in multiples of kB (1024 bytes)
-
uint32_t erase_size_au
Erase size for the purpose of timeout calculation, in multiples of allocation unit
-
uint32_t cur_bus_width
SD current bus width
-
uint32_t discard_support
SD discard feature support
-
uint32_t fule_support
SD FULE (Full User Area Logical Erase) feature support
-
uint32_t erase_timeout
Timeout (in seconds) for erase of a single allocation unit
-
uint32_t erase_offset
Constant timeout offset (in seconds) for any erase operation
-
uint32_t reserved
reserved for future expansion
-
uint32_t alloc_unit_kb
-
struct sdmmc_ext_csd_t
Decoded values of Extended Card Specific Data
-
struct sdmmc_switch_func_rsp_t
SD SWITCH_FUNC response buffer
Public Members
-
uint32_t data[512 / 8 / sizeof(uint32_t)]
response data
-
uint32_t data[512 / 8 / sizeof(uint32_t)]
-
struct sdmmc_command_t
SD/MMC command information
Public Members
-
uint32_t opcode
SD or MMC command index
-
uint32_t arg
SD/MMC command argument
-
sdmmc_response_t response
response buffer
-
void *data
buffer to send or read into
-
size_t datalen
length of data buffer
-
size_t blklen
block length
-
int flags
see below
-
uint32_t timeout_ms
response timeout, in milliseconds
-
uint32_t opcode
-
struct sdmmc_host_t
SD/MMC Host description
This structure defines properties of SD/MMC host and functions of SD/MMC host which can be used by upper layers.
Public Members
-
uint32_t flags
flags defining host properties
-
int slot
slot number, to be passed to host functions
-
int max_freq_khz
max frequency supported by the host
-
float io_voltage
I/O voltage used by the controller (voltage switching is not supported)
-
size_t (*get_bus_width)(int slot)
host function to get bus width
-
esp_err_t (*do_transaction)(int slot, sdmmc_command_t *cmdinfo)
host function to do a transaction
-
esp_err_t (*io_int_wait)(int slot, TickType_t timeout_ticks)
Host function to wait for SDIO interrupt line to be active
-
int command_timeout_ms
timeout, in milliseconds, of a single command. Set to 0 to use the default value.
-
uint32_t flags
-
struct sdmmc_card_t
SD/MMC card information structure
Public Members
-
sdmmc_host_t host
Host with which the card is associated
-
uint32_t ocr
OCR (Operation Conditions Register) value
-
sdmmc_cid_t cid
decoded CID (Card IDentification) register value
-
sdmmc_response_t raw_cid
raw CID of MMC card to be decoded after the CSD is fetched in the data transfer mode
-
sdmmc_csd_t csd
decoded CSD (Card-Specific Data) register value
-
sdmmc_scr_t scr
decoded SCR (SD card Configuration Register) value
-
sdmmc_ssr_t ssr
decoded SSR (SD Status Register) value
-
sdmmc_ext_csd_t ext_csd
decoded EXT_CSD (Extended Card Specific Data) register value
-
uint16_t rca
RCA (Relative Card Address)
-
uint16_t max_freq_khz
Maximum frequency, in kHz, supported by the card
-
uint32_t is_mem
Bit indicates if the card is a memory card
-
uint32_t is_sdio
Bit indicates if the card is an IO card
-
uint32_t is_mmc
Bit indicates if the card is MMC
-
uint32_t num_io_functions
If is_sdio is 1, contains the number of IO functions on the card
-
uint32_t log_bus_width
log2(bus width supported by card)
-
uint32_t is_ddr
Card supports DDR mode
-
uint32_t reserved
Reserved for future expansion
-
sdmmc_host_t host
Macros
-
SDMMC_HOST_FLAG_1BIT
host supports 1-line SD and MMC protocol
-
SDMMC_HOST_FLAG_4BIT
host supports 4-line SD and MMC protocol
-
SDMMC_HOST_FLAG_8BIT
host supports 8-line MMC protocol
-
SDMMC_HOST_FLAG_SPI
host supports SPI protocol
-
SDMMC_HOST_FLAG_DDR
host supports DDR mode for SD/MMC
-
SDMMC_HOST_FLAG_DEINIT_ARG
host
deinit
function called with the slot argument
-
SDMMC_FREQ_DEFAULT
SD/MMC Default speed (limited by clock divider)
-
SDMMC_FREQ_HIGHSPEED
SD High speed (limited by clock divider)
-
SDMMC_FREQ_PROBING
SD/MMC probing speed
-
SDMMC_FREQ_52M
MMC 52MHz speed
-
SDMMC_FREQ_26M
MMC 26MHz speed
Enumerations
-
enum sdmmc_erase_arg_t
SD/MMC erase command(38) arguments SD: ERASE: Erase the write blocks, physical/hard erase.
DISCARD: Card may deallocate the discarded blocks partially or completely. After discard operation the previously written data may be partially or fully read by the host depending on card implementation.
MMC: ERASE: Does TRIM, applies erase operation to write blocks instead of Erase Group.
DISCARD: The Discard function allows the host to identify data that is no longer required so that the device can erase the data if necessary during background erase events. Applies to write blocks instead of Erase Group After discard operation, the original data may be remained partially or fully accessible to the host dependent on device.
Values:
-
enumerator SDMMC_ERASE_ARG
Erase operation on SD, Trim operation on MMC
-
enumerator SDMMC_DISCARD_ARG
Discard operation for SD/MMC
-
enumerator SDMMC_ERASE_ARG