TS-4900 MicroSD Card Interface
The i.MX6 SDHCI driver supports MicroSD (0-2GB), MicroSDHC (4-32GB), and MicroSDXC(64GB-2TB). The cards available on our website on average support up to 16MB/s read, and 22MB/s write using this interface. The linux driver provides access to this socket at /dev/mmcblk1 as a standard Linux block device.
See chapter 67 of the i.MX6 reference manual for the specific CPU variant for more information on the mmc controller.
We have performed compatibility testing on the Sandisk MicroSD cards we provide. We do not suggest switching brands/models without your own qualification testing. While SD cards specifications are standardized, in practice cards behave very differently. We do not recommend ATP or Transcend MicroSD cards due to known compatibility issues.
Our testing has shown that on average microSD cards will last between 6-12TB. After this cards can begin to experience corruption, or stop being recognized by the host PC. This may be enough storage for many applications to write for years without problems. For more reliable storage consider using the eMMC. Our endurance testing showed a write lifetime on average of about 123 TiB.
MicroSD cards should not have power removed during a write or they will have disk corruption. Keep the filesystem mounted read only if this is a possibility. It is not always possible for fsck to recover from the types of failures that will be seen with SD power loss. Consider using the eMMC for storage instead which is far more resilient to power loss.