SDMMC Host Driver
Overview
ESP32-S3's SDMMC host peripheral has two slots. Each slot can be used independently to connect to an SD card, SDIO device, or eMMC chip.
Both slots SDMMC_HOST_SLOT_0
and SDMMC_HOST_SLOT_1
support 1-, 4- and 8-line SD interfaces. The slots are connected to ESP32-S3 GPIOs using the GPIO matrix. This means that any GPIO may be used for each of the SD card signals.
Supported Speed Modes
SDMMC Host driver supports the following speed modes:
Default Speed (20 MHz): 1-line or 4-line with SD cards, and 1-line, 4-line, or 8-line with 3.3 V eMMC
High Speed (40 MHz): 1-line or 4-line with SD cards, and 1-line, 4-line, or 8-line with 3.3 V eMMC
High Speed DDR (40 MHz): 4-line with 3.3 V eMMC
Speed modes not supported at present:
High Speed DDR mode: 8-line eMMC
UHS-I 1.8 V modes: 4-line SD cards
Using the SDMMC Host Driver
Of all the functions listed below, only the following ones will be used directly by most applications:
Other functions, such as the ones given below, will be called by the SD/MMC protocol layer via function pointers in the sdmmc_host_t
structure:
Configuring Bus Width and Frequency
With the default initializers for sdmmc_host_t
and sdmmc_slot_config_t
, i.e., SDMMC_HOST_DEFAULT
and SDMMC_SLOT_CONFIG_DEFAULT
, SDMMC Host driver will attempt to use the widest bus supported by the card (4 lines for SD, 8 lines for eMMC) and the frequency of 20 MHz.
In the designs where communication at 40 MHz frequency can be achieved, it is possible to increase the bus frequency by changing the max_freq_khz
field of sdmmc_host_t
:
sdmmc_host_t host = SDMMC_HOST_DEFAULT();
host.max_freq_khz = SDMMC_FREQ_HIGHSPEED;
If you need a specific frequency other than standard speeds, you are free to use any value from within an appropriate range of the SD interface given (SDMMC or SDSPI). However, the real clock frequency shall be calculated by the underlying driver and the value can be different from the one required.
For the SDMMC, max_freq_khz
works as the upper limit so the final frequency value shall be always lower or equal. For the SDSPI, the nearest fitting frequency is supplied and thus the value can be greater than/equal to/lower than max_freq_khz
.
To configure the bus width, set the width
field of sdmmc_slot_config_t
. For example, to set 1-line mode:
sdmmc_slot_config_t slot = SDMMC_SLOT_CONFIG_DEFAULT();
slot.width = 1;
Configuring GPIOs
ESP32-S3 SDMMC Host can be configured to use arbitrary GPIOs for each of the signals. Configuration is performed by setting members of sdmmc_slot_config_t
structure.
For example, to use GPIOs 1-6 for CLK, CMD, and D0-D3 signals respectively:
sdmmc_slot_config_t slot = SDMMC_SLOT_CONFIG_DEFAULT();
slot.clk = GPIO_NUM_1;
slot.cmd = GPIO_NUM_2;
slot.d0 = GPIO_NUM_3;
slot.d1 = GPIO_NUM_4;
slot.d2 = GPIO_NUM_5;
slot.d3 = GPIO_NUM_6;
It is also possible to configure Card Detect and Write Protect pins. Similar to other signals, set cd
and wp
members of the same structure:
slot.cd = GPIO_NUM_7;
slot.wp = GPIO_NUM_8;
SDMMC_SLOT_CONFIG_DEFAULT
sets both to GPIO_NUM_NC
, meaning that by default the signals are not used.
Once sdmmc_slot_config_t
structure is initialized this way, you can use it when calling sdmmc_host_init_slot()
or one of the higher level functions (such as esp_vfs_fat_sdmmc_mount()
).
DDR Mode for eMMC Chips
By default, DDR mode will be used if:
SDMMC host frequency is set to
SDMMC_FREQ_HIGHSPEED
insdmmc_host_t
structure, andeMMC chip reports DDR mode support in its CSD register
DDR mode places higher requirements for signal integrity. To disable DDR mode while keeping the SDMMC_FREQ_HIGHSPEED
frequency, clear the SDMMC_HOST_FLAG_DDR
bit in sdmmc_host_t::flags
field of the sdmmc_host_t
:
sdmmc_host_t host = SDMMC_HOST_DEFAULT();
host.max_freq_khz = SDMMC_FREQ_HIGHSPEED;
host.flags &= ~SDMMC_HOST_FLAG_DDR;
See also
SD/SDIO/MMC Driver: introduces the higher-level driver which implements the protocol layer.
SD SPI Host Driver: introduces a similar driver that uses the SPI controller and is limited to SD protocol's SPI mode.
SD Pull-up Requirements: introduces pull-up support and compatibilities of modules and development kits.
API Reference
Header File
This header file can be included with:
#include "driver/sdmmc_host.h"
This header file is a part of the API provided by the
driver
component. To declare that your component depends ondriver
, add the following to your CMakeLists.txt:REQUIRES driver
or
PRIV_REQUIRES driver
Functions
-
esp_err_t sdmmc_host_init(void)
Initialize SDMMC host peripheral.
Note
This function is not thread safe
- Returns
ESP_OK on success
ESP_ERR_INVALID_STATE if sdmmc_host_init was already called
ESP_ERR_NO_MEM if memory can not be allocated
-
esp_err_t sdmmc_host_init_slot(int slot, const sdmmc_slot_config_t *slot_config)
Initialize given slot of SDMMC peripheral.
On the ESP32, SDMMC peripheral has two slots:
Slot 0: 8-bit wide, maps to HS1_* signals in PIN MUX
Slot 1: 4-bit wide, maps to HS2_* signals in PIN MUX
Card detect and write protect signals can be routed to arbitrary GPIOs using GPIO matrix.
Note
This function is not thread safe
- Parameters
slot -- slot number (SDMMC_HOST_SLOT_0 or SDMMC_HOST_SLOT_1)
slot_config -- additional configuration for the slot
- Returns
ESP_OK on success
ESP_ERR_INVALID_STATE if host has not been initialized using sdmmc_host_init
-
esp_err_t sdmmc_host_set_bus_width(int slot, size_t width)
Select bus width to be used for data transfer.
SD/MMC card must be initialized prior to this command, and a command to set bus width has to be sent to the card (e.g. SD_APP_SET_BUS_WIDTH)
Note
This function is not thread safe
- Parameters
slot -- slot number (SDMMC_HOST_SLOT_0 or SDMMC_HOST_SLOT_1)
width -- bus width (1, 4, or 8 for slot 0; 1 or 4 for slot 1)
- Returns
ESP_OK on success
ESP_ERR_INVALID_ARG if slot number or width is not valid
-
size_t sdmmc_host_get_slot_width(int slot)
Get bus width configured in
sdmmc_host_init_slot
to be used for data transfer.- Parameters
slot -- slot number (SDMMC_HOST_SLOT_0 or SDMMC_HOST_SLOT_1)
- Returns
configured bus width of the specified slot.
-
esp_err_t sdmmc_host_set_card_clk(int slot, uint32_t freq_khz)
Set card clock frequency.
Currently only integer fractions of 40MHz clock can be used. For High Speed cards, 40MHz can be used. For Default Speed cards, 20MHz can be used.
Note
This function is not thread safe
- Parameters
slot -- slot number (SDMMC_HOST_SLOT_0 or SDMMC_HOST_SLOT_1)
freq_khz -- card clock frequency, in kHz
- Returns
ESP_OK on success
other error codes may be returned in the future
-
esp_err_t sdmmc_host_set_bus_ddr_mode(int slot, bool ddr_enabled)
Enable or disable DDR mode of SD interface.
- Parameters
slot -- slot number (SDMMC_HOST_SLOT_0 or SDMMC_HOST_SLOT_1)
ddr_enabled -- enable or disable DDR mode
- Returns
ESP_OK on success
ESP_ERR_NOT_SUPPORTED if DDR mode is not supported on this slot
-
esp_err_t sdmmc_host_set_cclk_always_on(int slot, bool cclk_always_on)
Enable or disable always-on card clock When cclk_always_on is false, the host controller is allowed to shut down the card clock between the commands. When cclk_always_on is true, the clock is generated even if no command is in progress.
- Parameters
slot -- slot number
cclk_always_on -- enable or disable always-on clock
- Returns
ESP_OK on success
ESP_ERR_INVALID_ARG if the slot number is invalid
-
esp_err_t sdmmc_host_do_transaction(int slot, sdmmc_command_t *cmdinfo)
Send command to the card and get response.
This function returns when command is sent and response is received, or data is transferred, or timeout occurs.
- Attention
Data buffer passed in cmdinfo->data must be in DMA capable memory
Note
This function is not thread safe w.r.t. init/deinit functions, and bus width/clock speed configuration functions. Multiple tasks can call sdmmc_host_do_transaction as long as other sdmmc_host_* functions are not called.
- Parameters
slot -- slot number (SDMMC_HOST_SLOT_0 or SDMMC_HOST_SLOT_1)
cmdinfo -- pointer to structure describing command and data to transfer
- Returns
ESP_OK on success
ESP_ERR_TIMEOUT if response or data transfer has timed out
ESP_ERR_INVALID_CRC if response or data transfer CRC check has failed
ESP_ERR_INVALID_RESPONSE if the card has sent an invalid response
ESP_ERR_INVALID_SIZE if the size of data transfer is not valid in SD protocol
ESP_ERR_INVALID_ARG if the data buffer is not in DMA capable memory
-
esp_err_t sdmmc_host_io_int_enable(int slot)
Enable IO interrupts.
This function configures the host to accept SDIO interrupts.
- Parameters
slot -- slot number (SDMMC_HOST_SLOT_0 or SDMMC_HOST_SLOT_1)
- Returns
returns ESP_OK, other errors possible in the future
-
esp_err_t sdmmc_host_io_int_wait(int slot, TickType_t timeout_ticks)
Block until an SDIO interrupt is received, or timeout occurs.
- Parameters
slot -- slot number (SDMMC_HOST_SLOT_0 or SDMMC_HOST_SLOT_1)
timeout_ticks -- number of RTOS ticks to wait for the interrupt
- Returns
ESP_OK on success (interrupt received)
ESP_ERR_TIMEOUT if the interrupt did not occur within timeout_ticks
-
esp_err_t sdmmc_host_deinit(void)
Disable SDMMC host and release allocated resources.
Note
This function is not thread safe
- Returns
ESP_OK on success
ESP_ERR_INVALID_STATE if sdmmc_host_init function has not been called
-
esp_err_t sdmmc_host_get_real_freq(int slot, int *real_freq_khz)
Provides a real frequency used for an SD card installed on specific slot of SD/MMC host controller.
This function calculates real working frequency given by current SD/MMC host controller setup for required slot: it reads associated host and card dividers from corresponding SDMMC registers, calculates respective frequency and stores the value into the 'real_freq_khz' parameter
- Parameters
slot -- slot number (SDMMC_HOST_SLOT_0 or SDMMC_HOST_SLOT_1)
real_freq_khz -- [out] output parameter for the result frequency (in kHz)
- Returns
ESP_OK on success
ESP_ERR_INVALID_ARG on real_freq_khz == NULL or invalid slot number used
-
esp_err_t sdmmc_host_set_input_delay(int slot, sdmmc_delay_phase_t delay_phase)
set input delay
This API sets delay when the SDMMC Host samples the signal from the SD Slave.
This API will check if the given
delay_phase
is valid or not.This API will print out the delay time, in picosecond (ps)
Note
ESP32 doesn't support this feature, you will get an
ESP_ERR_NOT_SUPPORTED
- Parameters
slot -- slot number (SDMMC_HOST_SLOT_0 or SDMMC_HOST_SLOT_1)
delay_phase -- delay phase, this API will convert the phase into picoseconds and print it out
- Returns
ESP_OK: ON success.
ESP_ERR_INVALID_ARG: Invalid argument.
ESP_ERR_NOT_SUPPORTED: ESP32 doesn't support this feature.
Structures
-
struct sdmmc_slot_config_t
Extra configuration for SDMMC peripheral slot
Public Members
-
gpio_num_t clk
GPIO number of CLK signal.
-
gpio_num_t cmd
GPIO number of CMD signal.
-
gpio_num_t d0
GPIO number of D0 signal.
-
gpio_num_t d1
GPIO number of D1 signal.
-
gpio_num_t d2
GPIO number of D2 signal.
-
gpio_num_t d3
GPIO number of D3 signal.
-
gpio_num_t d4
GPIO number of D4 signal. Ignored in 1- or 4- line mode.
-
gpio_num_t d5
GPIO number of D5 signal. Ignored in 1- or 4- line mode.
-
gpio_num_t d6
GPIO number of D6 signal. Ignored in 1- or 4- line mode.
-
gpio_num_t d7
GPIO number of D7 signal. Ignored in 1- or 4- line mode.
-
gpio_num_t gpio_cd
GPIO number of card detect signal.
-
gpio_num_t cd
GPIO number of card detect signal; shorter name.
-
gpio_num_t gpio_wp
GPIO number of write protect signal.
-
gpio_num_t wp
GPIO number of write protect signal; shorter name.
-
uint8_t width
Bus width used by the slot (might be less than the max width supported)
-
uint32_t flags
Features used by this slot.
-
gpio_num_t clk
Macros
-
SDMMC_SLOT_FLAG_INTERNAL_PULLUP
Enable internal pullups on enabled pins. The internal pullups are insufficient however, please make sure external pullups are connected on the bus. This is for debug / example purpose only.
-
SDMMC_SLOT_FLAG_WP_ACTIVE_HIGH
GPIO write protect polarity. 0 means "active low", i.e. card is protected when the GPIO is low; 1 means "active high", i.e. card is protected when GPIO is high.