microSD Card Connector Pinout
The 8-pin microSD interface — SD bus names with their SPI-mode equivalents.
Overview
A microSD card has 8 contacts. It speaks two protocols: the native SD bus (1- or 4-bit) and a simpler SPI mode that most microcontrollers use. The pin names below show the SD function with the SPI-mode role in parentheses.
In SPI mode you only need four signals plus power: CS (pin 2), MOSI/DI (pin 3), SCK (pin 5), and MISO/DO (pin 7). Cards run at 3.3V — use a level shifter on 5V boards.
Pinout
| Pin | Name | Function | Description |
|---|---|---|---|
| 1 | DAT2 | DATA | SD data 2 (unused in SPI). |
| 2 | CD/DAT3 (CS) | SPI | SD data 3 / SPI chip select. |
| 3 | CMD (DI/MOSI) | SPI | SD command / SPI MOSI. |
| 4 | VDD | POWER | 3.3V supply. |
| 5 | CLK (SCK) | SPI | Clock. |
| 6 | VSS | GND | Ground. |
| 7 | DAT0 (DO/MISO) | SPI | SD data 0 / SPI MISO. |
| 8 | DAT1 | DATA | SD data 1 (unused in SPI). |
Notes
- SPI mode uses pins 2 (CS), 3 (MOSI), 5 (SCK), 7 (MISO) + VDD/VSS.
- Cards are 3.3V — most breakout modules include a regulator and level shifter.
Reference: SD card physical layer (microSD)· verified 2026-06-21