Understanding SD, SDIO and MMC Interface

TL;DR; MMC and SD-card have the same physical and electrical specifications but different software controls. They both are used as storage devices only. SDIO and SD-Combo cards, on the other hand, incorporate Input/Output functionality (like Bluetooth, Wifi, GPS, etc) without and with the storage facility respectively. So, an SD-Combo card can act as a wifi adapter along with a storage device. In this blog post, I will present a summary of the following document http://www.kaltech.co.il/pdf/Eureka_sd_wp1.pdf. This is meant for anyone willing to understand how removable devices like sd cards work and the different protocols/functionalities they support. Secure Digital (SD) memory…

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