Micro SD Breakout Board
A few times I have needed to wire up a SD card to a STM32 MCU. Having no breakout board around I simply soldered some jumper leads to a Micro-SD to SD adapter (see STM32 SD card with FatFs) - which turns out to be harder than it sounds as the plastic adapter melt very easy. Trying to find a proper breakout board turned out to be hard. For some bizarre reason, the breakout boards available fall into two categories:
- 5V boards for Arduino (includes levels shifter)
- "Dumb" ones without proper pull-up resistors
For convenience we decided to create a simple breakout board with an SD Card connector in order to simply hook up SD cards to development boards using either SPI or SDIO. The specifications are simply:
- Must be using/running on 3.3V
- Must include necessary pull-up resistors
- Must work with both SPI and SDIO
Video
The design, development, pcb, ordering and use are described in the following video:
Schematics
The schematics design for this breakout board is (as most breakout boards) really simple.
Essentially the header is just connected straight to the Micro-SD socket with a pull-up resistor on each dataline (not the clock) and a couple of decoupling caps on the supply line to ensure a stable and relatively noise free supply.
PCB
The routing of the board is quite simple.
Silkscreen
On a breakout board such as this, the silkscreen is of utmost importance. On the bottom side we have added labels for both SDIO and SPI connections:
