esp-idf-sd-bench

sd card benchmark for esp-idf.
I wanted to know the writing performance of the SD card.
I modified this.

I used the ESP32-CAM development board.
ESP32-CAM development board comes with an SDMMC card reader.
I attached an SDSPI card reader to this board.
And I used the same micro SD card.

Installation for ESP32

git clone https://github.com/nopnop2002/esp-idf-sd-bench
cd esp-idf-sd-bench/
idf.py set-target esp32
idf.py menuconfig
idf.py flash

Configuration

For SDSPI

For SDMMC 4-line mode

For SDMMC 1-line mode

Wireing for SDSPI

ESP32 pin     | SD card pin | SPI pin | Notes
--------------|-------------|---------|------------
GPIO16        | D0          | MISO    |
GPIO13 (MTCK) | D3          | CS      | 
GPIO14 (MTMS) | CLK         | SCK     | 
GPIO15 (MTDO) | CMD         | MOSI    | 10k pullup 

Wireing for SDMMC

ESP32 pin     | SD card pin | Notes
--------------|-------------|------------
GPIO14 (MTMS) | CLK         | 10k pullup in SD mode
GPIO15 (MTDO) | CMD         | 10k pullup in SD mode
GPIO2         | D0          | 10k pullup in SD mode, pull low to go into download mode (see Note about GPIO2 below!)
GPIO4         | D1          | not used in 1-line SD mode; 10k pullup in 4-line SD mode
GPIO12 (MTDI) | D2          | not used in 1-line SD mode; 10k pullup in 4-line SD mode (see Note about GPIO12 below!)
GPIO13 (MTCK) | D3          | not used in 1-line SD mode, but card's D3 pin must have a 10k pullup

Using the 4-line SD mode on the ESP32 is a bit tricky.

Note about GPIO2 (ESP32 only)

GPIO2 pin is used as a bootstrapping pin, and should be low to enter UART download mode.
One way to solve this is to turn off the power to the SDMMC card reader when in UART download mode.
Another way to solve this is to connect GPIO0 and GPIO2 using a jumper, and then the auto-reset circuit on most development boards will pull GPIO2 low along with GPIO0, when entering download mode.

Note about GPIO12 (ESP32 only)

GPIO12 is used as a bootstrap pin to select the output voltage of the internal regulator(VDD_SDIO).
If GPIO12 is pulled up at reset, 1.8V will be output to VDD_SDIO.
If GPIO12 is pulled down at reset, 3.3V will be output to VDD_SDIO.
On boards that use an internal regulator(VDD_SDIO) and a 3.3V flash chip, GPIO12 must be low on reset.
4-line SD mode cannot be used with such boards.
In 1-line SD mode, GPIO12 is not used, so you can use the SDMMC card reader without any problems.

Another option is to burn the flash voltage selection efuses.
This will permanently select 3.3V output voltage for the internal regulator, and GPIO12 will not be used as a bootstrapping pin.
Then it is safe to connect a pullup resistor to GPIO12.
This option is suggested for production use.
The following command can be used to program flash voltage selection efuses to 3.3V:

    components/esptool_py/esptool/espefuse.py set_flash_voltage 3.3V

This command will burn the XPD_SDIO_TIEH, XPD_SDIO_FORCE, and XPD_SDIO_REG efuses.
With all three burned to value 1, the internal VDD_SDIO flash voltage regulator is permanently enabled at 3.3V.
See the technical reference manual for more details.

Benchmark

ESP32-CAM is equipped with an SDMMC card reader.
With the ESP32-CAM, you can use 4-line SD mode without any problems.
I attached an external SPI card reader to the ESP32-CAM, used the same micro SD card, and the same development board, and measured under the same conditions.

SoC	Freq(Mhz)	Interface	Highest(Kbyte/s)	Lowest(Kbyte/s)
ESP32	160	SDSPI	1282.6	55.8
ESP32	240	SDSPI	1462.0	256.9
ESP32	160	SDMMC(1-line)	2055.2	118.1
ESP32	240	SDMMC(1-line)	2076.3	365.3
ESP32	160	SDMMC(4-line)	5136.0	121.4
ESP32	240	SDMMC(4-line)	5310.8	115.7