SDMMC 主机驱动

[English]

概述

ESP32 的 SDMMC 主机外设共有两个卡槽,用于插入 SD 卡、连接 SDIO 设备或连接 eMMC 芯片,每个卡槽均可单独使用。

  • 卡槽 0 (SDMMC_HOST_SLOT_0) 为 8 位卡槽,使用 PIN MUX 中的 HS1_* 信号。

  • 卡槽 1 (SDMMC_HOST_SLOT_1) 为 4 位卡槽,使用 PIN MUX 中的 HS2_* 信号。

这些卡槽通过 IO MUX 连接到 ESP32 的 GPIO,其管脚映射如下表所示。

信号

卡槽 0

卡槽 1

CMD

GPIO11

GPIO15

CLK

GPIO6

GPIO14

D0

GPIO7

GPIO2

D1

GPIO8

GPIO4

D2

GPIO9

GPIO12

D3

GPIO10

GPIO13

D4

GPIO16

D5

GPIO17

D6

GPIO5

D7

GPIO18

CD

来自 GPIO 交换矩阵的任意输入

来自 GPIO 交换矩阵的任意输入

WP

来自 GPIO 交换矩阵的任意输入

来自 GPIO 交换矩阵的任意输入

可以通过 GPIO 交换矩阵将卡检测 (CD) 和写保护 (WP) 信号路由到任意管脚。为了保留这些管脚,需要先配置 sdmmc_slot_config_t 结构体的 cdwp,再调用 sdmmc_host_init_slot()。注意,使用 SDIO 卡时,不建议指定 CD 管脚,因为 ESP32 中的 CD 信号也可能触发 SDIO 从机设备中断。

警告

卡槽 0 使用的管脚 (HS1_*) 既用于连接主机上的 SD 卡插槽,也用于连接 ESP32-WROOM 和 ESP32-WROVER 模组中的 SPI flash 芯片,但这些管脚不能同时用于 SD 卡与 SPI flash。如需使用卡槽 0,请将 SPI flash 连接到其他管脚,并根据需要配置 eFuse。

支持的速率模式

SDMMC 主机驱动支持以下速率模式:

  • 默认速率 (20 MHz):对于 SD 卡,支持 1 线或 4 线传输;对于 3.3 V eMMC,支持 1 线、4 线或 8 线传输。

  • 高速模式 (40 MHz):对于 SD 卡,支持 1 线或 4 线传输;对于 3.3 V eMMC,支持 1 线、4 线或 8 线传输。

  • 高速 DDR 模式 (40 MHz):对于 3.3 V eMMC,支持 4 线传输。

当前尚不支持的速率模式:

  • 高速 DDR 模式:不支持 8 线 eMMC 传输

  • UHS-I 1.8 V 模式:不支持 4 线 SD 卡传输

使用 SDMMC 主机驱动

在大多数应用程序中,只有下列函数会被直接调用:

其他函数将通过 sdmmc_host_t 结构体中的函数指针由 SD/MMC 协议层调用,例如:

配置总线宽度和频率

使用 sdmmc_host_tsdmmc_slot_config_t 的默认初始化配置,即 SDMMC_HOST_DEFAULTSDMMC_SLOT_CONFIG_DEFAULT 时,SDMMC 主机驱动会尝试以当前卡所支持的最大总线宽度进行通信(SD 卡为 4 线,eMMC 为 8 线),并使用 20 MHz 的通信频率。

在支持 40 MHz 频率通信的设计中,可以调整 sdmmc_host_t 结构体中的 max_freq_khz 字段,提升总线频率:

sdmmc_host_t host = SDMMC_HOST_DEFAULT();
host.max_freq_khz = SDMMC_FREQ_HIGHSPEED;

如需选择标准速率以外的特定频率,请根据所使用的 SD 接口(SDMMC 或 SDSPI)确定适当频率范围,并选择其中的任意值。然而,实际的时钟频率会由底层驱动程序计算,可能与你所需的值不同。

使用 SDMMC 接口时,max_freq_khz 即频率上限,因此最终的频率值应始终低于该上限。而使用 SDSPI 接口时,驱动程序会提供最接近的适配频率,因此该值可以大于、等于或小于 max_freq_khz

请配置 sdmmc_slot_config_twidth 字段,配置总线宽度。例如,配置 1 线模式的代码如下:

sdmmc_slot_config_t slot = SDMMC_SLOT_CONFIG_DEFAULT();
slot.width = 1;

eMMC 芯片的 DDR 模式

默认情况下,如果满足以下条件,将使用 DDR 模式:

  • sdmmc_host_t 结构体中将 SDMMC 主机频率配置为 SDMMC_FREQ_HIGHSPEED,且

  • eMMC 芯片在其 CSD 寄存器中报告支持 DDR 模式

DDR 模式对信号完整性要求更高。如果要在保持 SDMMC_FREQ_HIGHSPEED 频率的同时禁用 DDR 模式,请在 sdmmc_host_t 结构体的 sdmmc_host_t::flags 字段中清除 SDMMC_HOST_FLAG_DDR 位:

sdmmc_host_t host = SDMMC_HOST_DEFAULT();
host.max_freq_khz = SDMMC_FREQ_HIGHSPEED;
host.flags &= ~SDMMC_HOST_FLAG_DDR;

相关文档

API 参考

Header File

  • components/esp_driver_sdmmc/include/driver/sdmmc_host.h

  • This header file can be included with:

    #include "driver/sdmmc_host.h"
    
  • This header file is a part of the API provided by the esp_driver_sdmmc component. To declare that your component depends on esp_driver_sdmmc, add the following to your CMakeLists.txt:

    REQUIRES esp_driver_sdmmc
    

    or

    PRIV_REQUIRES esp_driver_sdmmc
    

Functions

esp_err_t sdmmc_host_init(void)

Initialize SDMMC host peripheral.

备注

This function is not thread safe

返回

  • 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.

备注

This function is not thread safe

参数
  • slot -- slot number (SDMMC_HOST_SLOT_0 or SDMMC_HOST_SLOT_1)

  • slot_config -- additional configuration for the slot

返回

  • 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)

备注

This function is not thread safe

参数
  • 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)

返回

  • 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.

参数

slot -- slot number (SDMMC_HOST_SLOT_0 or SDMMC_HOST_SLOT_1)

返回

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.

备注

This function is not thread safe

参数
  • slot -- slot number (SDMMC_HOST_SLOT_0 or SDMMC_HOST_SLOT_1)

  • freq_khz -- card clock frequency, in kHz

返回

  • 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.

参数
  • slot -- slot number (SDMMC_HOST_SLOT_0 or SDMMC_HOST_SLOT_1)

  • ddr_enabled -- enable or disable DDR mode

返回

  • 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.

参数
  • slot -- slot number

  • cclk_always_on -- enable or disable always-on clock

返回

  • 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 and aligned to 4 byte boundary. If it's behind the cache, both cmdinfo->data and cmdinfo->buflen need to be aligned to cache line boundary.

备注

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.

参数
  • slot -- slot number (SDMMC_HOST_SLOT_0 or SDMMC_HOST_SLOT_1)

  • cmdinfo -- pointer to structure describing command and data to transfer

返回

  • 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.

参数

slot -- slot number (SDMMC_HOST_SLOT_0 or SDMMC_HOST_SLOT_1)

返回

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.

参数
  • slot -- slot number (SDMMC_HOST_SLOT_0 or SDMMC_HOST_SLOT_1)

  • timeout_ticks -- number of RTOS ticks to wait for the interrupt

返回

  • 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.

备注

This function is not thread safe

返回

  • 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

参数
  • slot -- slot number (SDMMC_HOST_SLOT_0 or SDMMC_HOST_SLOT_1)

  • real_freq_khz -- [out] output parameter for the result frequency (in kHz)

返回

  • 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)

备注

ESP32 doesn't support this feature, you will get an ESP_ERR_NOT_SUPPORTED

参数
  • 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

返回

  • 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 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.

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.