SD cards can be accessed with two modes. The first is the SDIO mode, which is what cameras, laptops, and other card readers use. The second mode is SPI mode. SPI is slower, but much, much simpler.

This project is an interactive Arduino-based piano that plays musical notes and a song stored on an SD card. It also includes a sound spectrum visualizer using an LED matrix, which reacts to the audio ...

A maker developer has squeezed an Arduino onto an SD card. He was inspired by Intel’s Edison compute module and he tried to go one better. The result is the SDuino, an ATMega328P processor-based ...

[Kevin] attached a MicroSD breakout board to an Arduino-compatible clone. When the clone starts up, it searches the SD card for a file called ‘program.hex.’ ...