class SDCard – secure digital memory card — MicroPython latest documentation (original) (raw)

SD cards are one of the most common small form factor removable storage media. SD cards come in a variety of sizes and physical form factors. MMC cards are similar removable storage devices while eMMC devices are electrically similar storage devices designed to be embedded into other systems. All three form share a common protocol for communication with their host system and high-level support looks the same for them all. As such in MicroPython they are implemented in a single class called machine.SDCard .

Both SD and MMC interfaces support being accessed with a variety of bus widths. When being accessed with a 1-bit wide interface they can be accessed using the SPI protocol. Different MicroPython hardware platforms support different widths and pin configurations but for most platforms there is a standard configuration for any given hardware. In general constructing an SDCard object with without passing any parameters will initialise the interface to the default card slot for the current hardware. The arguments listed below represent the common arguments that might need to be set in order to use either a non-standard slot or a non-standard pin assignment. The exact subset of arguments supported will vary from platform to platform.

SDCard(slot=1, width=1, cd=None, wp=None, sck=None, miso=None, mosi=None,

cs=None, cmd=None, data=None, freq=20000000)

This class provides access to SD or MMC storage cards using either a dedicated SD/MMC interface hardware or through an SPI channel. The class implements the block protocol defined by vfs.AbstractBlockDev. This allows the mounting of an SD card to be as simple as:

vfs.mount(machine.SDCard(), "/sd")

The constructor takes the following parameters:

• slot selects which of the available interfaces to use. Leaving this unset will select the default interface.
• width selects the bus width for the SD/MMC interface. This many data pins must be connected to the SD card.
• cd can be used to specify a card-detect pin.
• wp can be used to specify a write-protect pin.
• sck can be used to specify an SPI clock pin.
• miso can be used to specify an SPI miso pin.
• mosi can be used to specify an SPI mosi pin.
• cs can be used to specify an SPI chip select pin.

The following additional parameters are only present on ESP32 port:

• cmd can be used to specify the SD CMD pin (ESP32-S3 only).
• data can be used to specify a list or tuple of SD data bus pins (ESP32-S3 only).
• freq selects the SD/MMC interface frequency in Hz.

Implementation-specific details¶

Different implementations of the SDCard class on different hardware support varying subsets of the options above.

PyBoard¶

The standard PyBoard has just one slot. No arguments are necessary or supported.

ESP32¶

SD cards support access in both SD/MMC mode and the simpler (but slower) SPI mode.

SPI mode makes use of a SPI host peripheral, which cannot concurrently be used for other SPI interactions.

The slot argument determines which mode is used. Different values are supported on different chips:

Different slots support different data bus widths (number of data pins):

Note

Most ESP32 modules that provide an SD card slot using the dedicated hardware only wire up 1 data pin, so the default value for width is 1.

Additional details depend on which ESP32 family chip is in use:

Original ESP32¶

In SD/MMC mode (slot 1), pin assignments in SD/MMC mode are fixed on the original ESP32. The SPI mode slots (2 & 3) allow pins to be set to different values in the constructor.

The default pin assignments are as follows:

Slot	1	2	3	Can be set
Signal	Pin	Pin	Pin
CLK	14	No
CMD	15	No
D0	2	No
D1	4	No
D2	12	No
D3	13	No
sck	18	14	Yes
cs	5	15	Yes
miso	19	12	Yes
mosi	23	13	Yes

The cd and wp pins are not fixed in either mode and default to disabled, unless set.

ESP32-S3¶

The ESP32-S3 chip allows pins to be set to different values for both SD/MMC and SPI mode access.

If not set, default pin assignments are as follows:

Slot	0	1	2	3
Signal	Pin	Pin	Pin	Pin
CLK	14	14
CMD	15	15
D0	2	2
D1	4	4
D2	12	12
D3	13	13
D4	33*
D5	34*
D6	35*
D7	36*
sck	37*	14
cs	34*	13
miso	37*	2
mosi	35*	15

Note

Slots 0 and 1 cannot both be in use at the same time.

Note

Pins marked with an asterisk * in the table must be changed from the default if the ESP32-S3 board is configured for Octal SPI Flash or PSRAM.

To access a card in SD/MMC mode, set slot parameter value 0 or 1 and parameters sck (for CLK), cmd and data as needed to assign pins. If the data argument is passed then it should be a list or tuple of data pins or pin numbers with length equal to the width argument. For example:

sd = SDCard(slot=0, width=4, sck=8, cmd=9, data=(10, 11, 12, 13))

To access a card in SPI mode, set slot parameter value 2 or 3 and pass parameters sck, cs, miso, mosi as needed to assign pins.

In either mode the cd and wp pins default to disabled, unless set in the constructor.

Other ESP32 chips¶

Other ESP32 family chips do not have hardware SD/MMC host controllers and can only access SD cards in SPI mode.

To access a card in SPI mode, set slot parameter value 2 or 3 and pass parameters sck, cs, miso, mosi to assign pins.

Note

ESP32-C3 and ESP32-C6 only have one available SPI bus, so the only valid slot parameter value is 2. Using this bus for the SD card will prevent also using it for machine.SPI.

cc3200¶

You can set the pins used for SPI access by passing a tuple as the_pins_ argument.

Note: The current cc3200 SD card implementation names the this classmachine.SD rather than machine.SDCard .

mimxrt¶

The SDCard module for the mimxrt port only supports access via dedicated SD/MMC peripheral (USDHC) in 4-bit mode with 50MHz clock frequency exclusively. Unfortunately the MIMXRT1011 controller does not support the USDHC peripheral. Hence this controller does not feature the machine.SDCard module.

Due to the decision to only support 4-bit mode with 50MHz clock frequency the interface has been simplified, and the constructor signature is:

class machine.SDCard(slot=1)

The pins used for the USDHC peripheral have to be configured in mpconfigboard.h. Most of the controllers supported by the mimxrt port provide up to two USDHC peripherals. Therefore the pin configuration is performed using the macroMICROPY_USDHCx with x being 1 or 2 respectively.

The following shows an example configuration for USDHC1:

#define MICROPY_USDHC1
{
.cmd = { GPIO_SD_B0_02_USDHC1_CMD},
.clk = { GPIO_SD_B0_03_USDHC1_CLK },
.cd_b = { GPIO_SD_B0_06_USDHC1_CD_B },
.data0 = { GPIO_SD_B0_04_USDHC1_DATA0 },
.data1 = { GPIO_SD_B0_05_USDHC1_DATA1 },
.data2 = { GPIO_SD_B0_00_USDHC1_DATA2 },
.data3 = { GPIO_SD_B0_01_USDHC1_DATA3 },
}

If the card detect pin is not used (cb_b pin) then the respective entry has to be filled with the following dummy value:

#define USDHC_DUMMY_PIN NULL , 0

Based on the definition of macro MICROPY_USDHC1 and/or MICROPY_USDHC2the machine.SDCard module either supports one or two slots. If only one of the defines is provided, calling machine.SDCard() or machine.SDCard(1)will return an instance using the respective USDHC peripheral. When both macros are defined, calling machine.SDCard(2) returns an instance using USDHC2.