Why Your Embedded System Doesn't Recognize a New microSD Card: SDSC vs. SDHC Explained
A familiar situation in service and maintenance: the microSD card in an older measuring device, controller or terminal fails. A technician inserts a new card, a brand-name product with plenty of capacity, and the device reports "no card", "card error" or simply does not start. The new card is not defective. In most cases the problem is a mismatch between the card's capacity class and what the device can handle. Many embedded systems were designed when microSD cards had a few hundred megabytes or a few gigabytes. Their firmware and hardware only support the original SD standard capacity class, called SDSC. Today's consumer cards are almost all SDHC or SDXC, and a device that only knows SDSC cannot use them. This article explains the SD capacity classes, why older devices reject newer cards, how to diagnose the problem and how to find the right replacement card. The SD capacity classes The SD Association defines capacity classes for SD and microSD cards. Eac...
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