Digging Deep Into SD Card Secrets

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To some, an SD card is simply an SD card, notable only for the amount of storage it provides as printed on the label. However, just like poets, SD cards contain¬†multitudes.¬†[Jason Gin] was interested as to what made SanDisk’s High Endurance line of microSDXC cards tick, so he set out to investigate.

Naturally, customer service was of no help. Instead, [Jason] started by scraping away the epoxy covering which hides the card’s test points. Some delicate soldering was required to hook up the test points to a breakout board, while also connecting the SD interface to a computer to do its thing. A DS Logic Plus signal analyzer was used to pick apart the signals going to the chip to figure out what was going on inside.

After probing around, [Jason] was able to pull out the NAND Flash ID, which, when compared to a Toshiba datasheet, indicates the card uses BiCS3 3D TLC NAND Flash. 3D NAND Flash has several benefits over traditional planar Flash technology, and SanDisk might have saved [Jason] a lot of time investigating if they’d simply placed this in their promotional material.

We’ve seen other similar hacks before, like this data recovery performed via test points. If you’ve been working away on SD cards in your own workshop, be sure to let us know!