STM32 SD card

Micro-SD Adaptor with jumper leads soldered on

In this article we will be interfacing a SD-card using STM32.

SD-Card Pinout

The pinout of a SD-card and a MicroSD-card are as follows:

It is important to notice that all SD-cards can be interfaced in two different ways:

1. SDIO
2. SPI

DIY SD-card Adaptor

A quick way to hook up a SD-card to a STM32 is to use one of those SD to Micro-SD adaptors that come with most Micro-SD's when you buy them. I made one looking like this:

Combining that with the pinout from the previous section, we can make the following table:

Pin	Color	SDIO	SPI
1	White	CD/Dat3	CS
2	Grey	CMD	DI
3	Purple	VSS1	VSS1
4	Blue	VDD	VDD
5	Green	CLK	SCLK
6	Yellow	VSS2	VSS2
7	Orange	DAT0	DO
8	Red	DAT1
9	Black	DAT2

As per the SD-card specification in both the case of SPI and SDIO, all signals except the clock should be pulled up. Our DIY adaptor does not include pull-up resistors, so we will have to rely on the internal ones, which are really quite weak.

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