Pinout
SD card (SPI mode) pinout

Pins
- 1: CS (DAT3, chip select)
- 2: MOSI (CMD/DI, master → card)
- 3: GND
- 4: VDD (3.3V)
- 5: CLK (SCLK)
- 6: GND
- 7: MISO (DAT0/DO, card → master)
- 8/9: DAT1/DAT2 — unused in SPI mode
Specifications
| Contacts | 9 (SD), 8 (microSD) |
|---|---|
| Supply | 2.7–3.6 V |
| Logic level | 3.3 V, not 5 V tolerant |
| SPI mode | Mode 0 |
| Init clock | 100–400 kHz |
| Max SPI clock | 25 MHz (default speed) |
| Capacity | SDSC ≤ 2 GB, SDHC ≤ 32 GB, SDXC ≤ 2 TB |
| Card size | 32 × 24 × 2.1 mm (SD), 15 × 11 × 1 mm (microSD) |







