Verified 2026-10
MicroSD card breakout board+
An 8-pad SPI microSD socket that a 5 V board can drive directly: a 74HC4050 buffer shifts 3.3-5 V host logic down to the card's 3.3 V and an onboard ultra-low-dropout regulator (IC2) makes that 3.3 V from a 3.3-6 V supply; 31.85 x 25.4 x 3.75 mm without the 0.1in header.
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Pinout
8 pads, as the vendor numbers them.
| # | Name | Function | Signals |
|---|---|---|---|
| 1 | 5V | Supply input to the onboard regulator; the tutorial wires this to the host's 5 V pin, and the regulator accepts 3.3-6 V | supply input, LDO input |
| 2 | 3V | Regulated 3.3 V output of IC2 - the rail the card and level shifter run from | 3.3 V output, regulated rail |
| 3 | GND | Common ground for supply and logic | ground |
| 4 | CLK | SPI clock; the tutorial connects it to Arduino D13 (Mega D52) | SPI SCK, input |
| 5 | DO | Data out of the card, i.e. SPI MISO; tutorial: Arduino D12 (Mega D50). The board silkscreens a direction arrow away from the board on this pad | SPI MISO, output |
| 6 | DI | Data into the card, i.e. SPI MOSI; tutorial: Arduino D11 (Mega D51) | SPI MOSI, input |
| 7 | CS | Card chip select; tutorial: Arduino D10 (Mega D53), and the vendor notes any other pin works | SPI CS, input |
| 8 | CD | Card detect: shorts to ground when no card is inserted, so it needs an external 10 kOhm pull-up if it is used at all; Adafruit warns some card holders are wired the other way round | card detect, switch to ground |
Buses
| Bus | Signals | Pins | Voltage | Note |
|---|---|---|---|---|
| SPI ×1 | SCK, MOSI, MISO, CS | CLK, DI, DO, CS |
Power
| Input | 5 V into the 5V pad (the vendor's wiring page connects it to the Arduino's 5 V pin), or 3.3-6 V anywhere in that range; the onboard LDO regulates down to ~3.3 V |
|---|---|
| Input range | 3.3-6 V |
The 3V pad is the LDO's regulated 3.3 V output, not a second supply input. Adafruit publishes no board-level current draw, so none is recorded; the 3.43 g / 3.75 mm-high figures on the product page are mechanical only.
Notes
The vendor prints no pin numbers. The 1-8 here are the Eagle fab file's own JP1 pad numbers, and the fab file pins that numbering to the silkscreen: pad 1 sits at the 5V end of the single 8-pad row and pad 8 at the CD end (silk names '5v, 3v, GND, CLK, DO, DI, CS, CD' read off the same file, and the same top-to-bottom order CD-CS-DI-DO-CLK-GND-3v-5v on the product photo). The row is 0.1in pitch. Two things a designer gets wrong: 3V is an output (back-feeding it fights the LDO), and this is the 'board+' revision with the level shifter and LDO fitted - Adafruit sells a separate 'Micro SD SPI or SDIO Card Breakout - 3V ONLY!' that is not this board and must not be powered from 5 V. Decoupling/current draw is unpublished.
Provenance
Every figure on this page was read from the 3 sources below and last checked on Oct 18, 2026.
- vendor Adafruit - MicroSD card breakout board+ product page (ID 254, $7.50; 31.85 x 25.4 x 3.75 mm, 3.43 g without the header)
- reference Adafruit learn - Micro SD Card Breakout Board Tutorial, Arduino Wiring (3.3-6 V regulator, 3.3-5 V level shifter, CLK/DO/DI/CS wiring, CD pull-up)
- datasheet Adafruit - microSD breakout Eagle fab file (JP1 pads 1-8, silk 5v / 3v / GND / CLK / DO / DI / CS / CD)