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SD Card Guide

The Omega4 EVB includes a push-push MicroSD slot wired to the SoC's SDMMC controller so you can add removable storage. The interface runs at 3.3 V and supports standard SDHC/SDXC cards; UHS-I cards run in backward-compatible modes. On the EVB the card appears as /dev/mmcblk1 (partition /dev/mmcblk1p1).

1. Requirements​

  • Omega4 firmware with the SDMMC controller enabled. Images built from this tree already include the required drivers. If /dev/mmcblk1 never appears, ensure the device tree keeps the SDMMC node enabled and install the MMC kernel modules (kmod-mmc-core, kmod-mmc-rockchip or the equivalent for your build).
  • A known-good MicroSD card (FAT32/exFAT/ext4 work; exFAT needs the kmod-fs-exfat package).
  • Optional packages for formatting: opkg update && opkg install fdisk e2fsprogs kmod-fs-ext4 dosfstools.

2. Insert and verify detection​

  1. Insert the MicroSD card until it clicks into the EVB slot.
  2. Confirm the controller and partition are detected (the SD card shows up as mmcblk1 on the EVB):
dmesg | grep -i mmc
cat /proc/partitions
# optional if block-mount is installed: block info

3. Mount an existing partition​

Use mount to attach the filesystem manually. Adjust the partition name if your card has multiple partitions.

mkdir -p /mnt/sdcard
mount -t auto /dev/mmcblk1p1 /mnt/sdcard
df -h /mnt/sdcard

If the card is exFAT, you can skip filesystem probing (and the noisy f2fs warnings) by specifying the type explicitly:

mount -t exfat /dev/mmcblk1p1 /mnt/sdcard

If you see unknown filesystem type, install the matching filesystem package (for example kmod-fs-ext4 + e2fsprogs for ext4, kmod-fs-exfat for exFAT).

4. Format the card (optional, destructive)​

Only do this if you are sure you can erase the card.

opkg update
opkg install fdisk e2fsprogs kmod-fs-ext4 dosfstools
fdisk /dev/mmcblk1          # create a single primary partition (p1)
mkfs.ext4 /dev/mmcblk1p1    # or mkfs.vfat /dev/mmcblk1p1 for FAT32

Remount the new filesystem:

mount /dev/mmcblk1p1 /mnt/sdcard

5. Auto-mount on boot​

Add an fstab entry so the card mounts to /mnt/sdcard at startup:

uci add fstab mount
uci set fstab.@mount[-1].target='/mnt/sdcard'
uci set fstab.@mount[-1].device='/dev/mmcblk1p1'
uci set fstab.@mount[-1].fstype='ext4'   # change if you formatted differently
uci set fstab.@mount[-1].enabled='1'
uci commit fstab
/etc/init.d/fstab restart

Reboot or run mount /mnt/sdcard to verify the entry works.

6. Safe removal​

Always flush and unmount before ejecting to avoid corruption:

sync
umount /mnt/sdcard

Then press the card inward to release it from the push-push slot.

7. Troubleshooting​

  • /dev/mmcblk0 missing: reseat the card, check dmesg | grep -i mmc for power or tuning errors, and confirm the SDMMC node is okay in the DTS.
  • Mount errors about filesystem type: install the matching filesystem kernel module/tools or reformat to a supported type (ext4/FAT32 are safe defaults).
  • Intermittent I/O errors: test with a different card, ensure solid 5 V supply to the EVB, and avoid very high-draw peripherals on the same rail.