Unable to connect to SD card via SPI

RE: Unable to connect to SD card via SPI

aniederberger — Mon, 11 Nov 2024 01:06:29 GMT

Looking at the SPI signals showed that the chip-select pin is never pulled low, which I interpret as disk_access_init(DISK_NAME) not being able to find the (correct) SD card Devicetree entry. Therefore, my hunch is that the problem is either in how I am defining the label in the overlay and/or in the prj.conf file. In fact, src/main.c shows that device_get_binding(...) is able to locate the Devicetree entry. In contrast, I found diving into the source code that disk_access_init(...), which tries to locate the Devicetree entry using disk_access_get_di(...) cannot. Thoughts?

PS: For reference, I am pasting below:

the corrected overlay file: I played with putting the label property at different places in the overlay structure but it did not seem to make a difference. Also, I tried different psi-max-frequency values ranging from 240k to 24M without success. Please note that the Zephyr documentation on Disk Access defines the cs-gpios as &porta, not as &gpio0, and it does not use label, but disk-name, which leads to a compilation error on my system.
src/main.c file without the debugging for-loop (which repeats the connection attempt 100 times) for simplicity.
prj.conf now including the LOG and GPIO configs just in case; I played with that adding and removing lines but could not get it to work properly. Is there a config that I should add and don't know about?
nRF Serial Terminal output showing that the device binding works vial the label property but not when trying to initialize disk access.

// boards/nrf52dk_nrf52832.overlay:

&spi1 {
    status = "okay";
    cs-gpios = <&gpio0 28 GPIO_ACTIVE_LOW>;
    sdhc0: sdhc@0 {
            compatible = "zephyr,sdhc-spi-slot";
            reg = <0x0>;
            status = "okay";
            label="SD";
            mmc {
                compatible = "zephyr,sdmmc-disk";
                status = "okay";
            };
            spi-max-frequency = <24000000>;
    };
};

// src/main.c: 

#include <zephyr/device.h>
#include <zephyr/drivers/disk.h>
#include <zephyr/storage/disk_access.h>
#include <zephyr/logging/log.h>

LOG_MODULE_REGISTER(sd_problem, LOG_LEVEL_INF);

#define DISK_NAME "SD"

int main(void) {
    const struct device *SD_dev = device_get_binding(DISK_NAME);
    LOG_INF("SD_dev pointer address: %i; name: %s.", (int)SD_dev, SD_dev->name);
    int ret = disk_access_init(DISK_NAME);
    if (ret) {
        LOG_ERR("Failed to initialize SD card: %i", ret);

    } else {
        LOG_INF("Successfully initialized SD card");
    return 0;
}

# prj.conf:

CONFIG_GPIO=y
CONFIG_LOG=y
CONFIG_SPI=y
CONFIG_DISK_ACCESS=y
CONFIG_DISK_DRIVERS=y
CONFIG_SDMMC_STACK=y
CONFIG_SPI_NRFX=y
CONFIG_SDHC=y

# serial terminal output:

*** Booting nRF Connect SDK v2.7.0-5cb85570ca43 ***
*** Using Zephyr OS v3.6.99-100befc70c74 ***
[00:00:00.460,388] <inf> sd_problem: SD_dev pointer address: 36708; name: SD.
[00:00:00.460,418] <err> sd_problem: Failed to initialize SD card: -22

RE: Unable to connect to SD card via SPI

aniederberger — Sat, 09 Nov 2024 19:35:36 GMT

Good catch. Just implemented the GPIO_ACTIVE_LOW change in the overlay file and I checked with my logic analyzer (for-loop with 100 repeated attempts at initializing). Same as before: no activity on SPI pins, and disk_access_init() returns -22.

RE: Unable to connect to SD card via SPI

Turbo J — Sat, 09 Nov 2024 19:29:46 GMT

CS is an active low signal, try GPIO_ACTIVE_LOW in the overlay.

A logic analyser is recommended.

RE: Unable to connect to SD card via SPI

aniederberger — Sat, 09 Nov 2024 19:11:45 GMT

Hi Turbo J,
Thanks for your reply. Yes, I believe that something like what you are suggesting will be the solution. I have tried variants of the following overlay and I was able to get it to compile, but not to connect to the disk.

Here is the an overlay file I used similar to what you are suggesting. Note that I am using the depricated property "label", here. What is the current way to connect to such a device?

// boards/nrf52dk_nrf52832.overlay:

&spi0 { status = "disabled";};
&i2c1 { status = "disabled";};

&spi1 {
    status = "okay";
    cs-gpios = < &gpio0 28 GPIO_ACTIVE_HIGH >;
    label = "SD";
    sdhc-spi-slot@0 {
        compatible = "zephyr,sdhc-spi-slot";
        status = "okay";
        reg = <0x0 >;
        spi-max-frequency = <8000000>;
        
        mmc {
            compatible = "zephyr,sdmmc-disk";
            status = "okay";
        };  
    };
};

It seems that the problem is precisely between the Devicetree and main.c working with the correct GPIO ports to do the SPi. In fact, I tried disk_access_init("SD") using this overlay file but was never able to initialize the SD card, always getting error code -22, and I never even saw any communications when checking with my oscilloscope.

RE: Unable to connect to SD card via SPI

Turbo J — Sat, 09 Nov 2024 10:00:04 GMT

I believe its in the DTS from some of the SD card examples, but you need to know what to look for:

sdhc0: sdhc@0 {
		compatible = "zephyr,sdhc-spi-slot";
		reg = <0x0 >;
// ... more stuff here, skipped
        mmc {
			compatible = "zephyr,sdmmc-disk";
			status = "okay";
			
		};
    };

The "Disk" part is on an internal node - maybe in order to support other SDIO cards. But these typically don't support SPI mode.