Rhomb.io uSD Card Holder module
A micro SD Card holder module 100% compliant with the Rhomb.io ecosystem
This example demonstrates how to use the Mbed OS file system on target RHOMBIO_L476DMW1K together with a Rhombio uSD Holder module. The example is based on mbed official mbed-os-example-filesystem with minor modifications.
SD Cards are widely used by loads of devices for storage; phones, mp3 players, pc's etc. That means they are a very cheap option for storing large amounts of non-volatile data (i.e. the data is not lost when the power is removed). They should be ideal for data logging and storing audio/images.
SD and MMC cards support various protocols, but common to them all is one based on SPI. This is the one used here as, whilst not being the most high performance, it uses a generic SPI interface so will be more portable.
SD Cards are block devices. That means you read/write data in multiples of the block size (usually 512-bytes); the interface is basically "read from block address n", "write to block address m". Note that a filesystem (e.g. FAT) is an abstraction on top of this, and the disk itself knows nothing about the filesystem.