What is a Micro SD Card : Pin Configuration & Its Interfacing

At present, compact storage solutions are crucial for almost every gadget which uses SD cards. Because every day the amount of data used by people is increasing & the size of memory cards have become increasingly smaller & cheaper. Micro SD card is simply available in small size, but they offer sufficient memory for different files. These cards are accessible in different sizes of memory & speed classes. There are different ways available to store & use the important data when you need it.

What is a Micro SD Card?

In micro SD card, SD stands for “Secure Digital” and it is a non-volatile memory card that means a type of computer memory that keeps the stored data even after a power supply is detached. This format was developed by the SDA organization to utilize portable devices.

Micro SD Card
Micro SD Card

The smallest SD memory card was launched in the year 2005 & extensively used in tablets, handheld devices, smartphones, etc. This type of memory card is electrically & compatible with software through the full-size secure digital card.

Memory cards play a key role due to their small size, less weight and we can fit them into the slots of smartphones. Memory cards are available in different capacities from different storage brand companies like Samsung, SanDisk Strontium Nitro, and Micro SD Card with different memories.

The alternate versions of the SC card include SDHC & SDXC and its weight is below one gram. The SD cards/Micro SD cards are extensively used in different applications like data logging, visualization, etc. These SD cards can be accessed easily through an adapter module of a micro SD card. This module is very simple to use with an SPI interface & a 3.3V voltage regulator is used to give proper supply to the SD card.

Micro SD Card Pin Configuration

The pin configuration of the micro SD card module is shown below. This module includes six pins to provide power & interacting through the controller. So in the following, each type of pin is described with its functionality.

Micro SD Card Pin Configuration
Micro SD Card Pin Configuration
  • GND pin connects to the ground terminal
  • VCC is a voltage input pin
  • MISO is a master in slave out pin
  • MOSI is a master out slave in(SPI)
  • SCK is a serial clock pin
  • CS is a chip select pin

Features & Specifications

The features & specifications of the micro SD card adapter module include the following.

  • Operating voltage ranges from 4.5Volts to 5.5Volts DC
  • Required current supply ranges from 0.2 to 200 mA
  • The onboard voltage regulator is 3.3V
  • It supports FAT file system micro SD capable of 2GB & Micro SDHC capable of 32GB

Types of Micro SD Cards

MicroSD cards are available in three types which vary in terms of memory size & file systems.

  • The capacity of MicroSD cards is 2GB and the file system used for formatting is the FAT16.
  • MicroSDHC cards capacity ranges from 4GB to 32GB & the file system used for formatting is FAT32.
  • MicroSDXC cards capacity ranges from 48GB to 2TB & its formatting can be done through the exFAT system.
  • MicroSD cards are available with the SanDisk Ultra microSDXC – 64GB & 128GB. So with such a huge storage volume, full HD video & high-quality photos can be recorded & stored continuously.

Speed Classes

The speed classes of MicroSD cards are various & they are separated into different types like speed class 2, speed class 4, speed class 6 & speed class 10. When the speed class number is high then data transfer can be done very fast.

Here this value communicates to the least transmission of the data within MB for each second (MB/s). Based on this, a speed class 4 card can transmit the data through a minimum of 4 MB / s.

The typical ultra high speed or UHS is accessible for SDXC & SDHC cards. Here, UHS-I is capable of data transmitting at 10 MB/s, whereas UHS-II speed is a minimum of 30 MB/s.

The specification must be supported by the terminal and memory card. A 32GB UHS-I SanDisk Extreme PRO MicroSDHC is the ideal companion for anybody who needs to take pictures with Full HD & 4K Ultra HD video. Similarly, the 128GB UHS-I provides even more area for storage.

Along with the UHS Speed Class & Speed Class, the Speed Class for Video is one more indicator for speed. So the speed class of video mainly comprises of the V6 & V10 & V30 & V60 & V90.

The above-mentioned memory cards are perfect to record 360 degrees video with virtual reality through a Class 30 video speed. The memory card storage is accessible in different versions like 32, 64 &128GB.

Speed Rating

The speed rating on the microSD card can occasionally be found, which gives data regarding the highest speed of reading. So this value advises you how many times quicker the MicroSD card functions as evaluated to the CD drive. Here, the number is merged through the x-factor, that is, the easy speed of reading for a CD drive is 150 KB/s. A 1800x factor corresponds to a speed of reading roughly 270 MB/s.

How to Choose MicroSD Cards?

There are different types of memory cards available in the market based on the application or requirement like SD, Compact Flash, SDHC, MicroSD, SDXC, etc.

Before selecting a MicroSD card, you have to verify always which types of cards are suitable for your device because not all devices support all formats & capacities. To keep away from a fault, you must also consider the reason for which the memory card is required.

  • Based on size, capacity & speed
  • For cameras, U1/V10 and C10 are used
  • For full HD & 4K video recording, V30 or U3 are the best choices. An Ultra High Speed (UHS) card must be selected if the fatal also supports this condition

Interfacing MicroSD Card with Arduino Board

The MicroSD card module is capable of transferring data to & from a typical secure digital card or SD card. This memory module includes an SPI interface that is well-suited with any memory card. The power supply used by this memory card is 3.3V or 5V which is well-matched through Arduino boards like Arduino Mega or Arduino UNO

MicroSD Card Module
MicroSD Card Module

The interfacing diagram of the Arduino board with the SD card is shown below.

Interfacing MicroSD Card with Arduino Board
Interfacing MicroSD Card with Arduino Board
  • MOSI pin of the SD card is connected to pin 11 of Arduino
  • MISO pin of the SD card is connected to pin 12 of the Arduino
  • CLK pin of the SD card is connected to pin 13 of the Arduino
  • CS pin of the SD card is connected to pin 4 of Arduino
  • Here VCC of the MicroSD card module can be connected to either 3.3v or 5v.

The read and write operation on Arduino can be performed by interfacing the micro SD card through Arduino. Here the inbuilt code is taken from Arduino IDE and the library files used by this code are two types like SPI.h & SD.h.

These files include definitions of direct functions that are mainly utilized to read and write memory cards’ operations.

To access the code within Arduino IDE, we have to follow the steps mentioned below.
Open IDE –>Select Files –> Click on examples –>Choose MicroSD card –>Open Read/Write

#include <SPI.h>
#include <SD.h>
File myFile;
void setup() {
// Open serial communications and wait for port to open:
while (!Serial) {
; // wait for serial port to connect. Needed for native USB port only
Serial.print(“Initializing SD card…”);
if (!SD.begin(4)) {
Serial.println(“initialization failed!”);
Serial.println(“initialization done.”);
// open the file. note that only one file can be open at a time,
// so you have to close this one before opening another.
myFile = SD.open(“test.txt”, FILE_WRITE);
// if the file opened okay, write to it:
if (myFile) {
Serial.print(“Writing to test.txt…”);
myFile.println(“testing 1, 2, 3.”);
// close the file:
} else {
// if the file didn’t open, print an error:
Serial.println(“error opening test.txt”);
// re-open the file for reading:
myFile = SD.open(“test.txt”);
if (myFile) {
// read from the file until there’s nothing else in it:
while (myFile.available()) {
// close the file:
} else {
// if the file didn’t open, print an error:
Serial.println(“error opening test.txt”);
void loop() {
// nothing happens after setup

Advantages & Disadvantages

The advantages of a microSD card include the following.

  • Storage can be increased
  • Commercial
  • Phone memory consumption can be reduced
  • Portable
  • Removable
  • Need Less Power
  • Simply Accessed on Personal Computer
  • Non-volatile Memory

The disadvantages of microSD cards include the following.

  • Easily damaged
  • Physically not strong
  • Finite Read or Write Cycles
  • Phone performance can be damaged through less class memory card
  • Not fast as compared to primary memory
  • Once the card is removed then apps can be disappeared


The microSD card is a small removable flash memory card, used to contain huge data. But still larger devices depend on normal SD cards as they support high capacities of data, however, in specific devices like dashcams, smartphones, small cameras mainly depend on the microSD card due to its small shape.

This type of memory card is particularly made for mobile phones. Similar to any flash memory, this memory card is used to store different types of files like music, videos, photos, software, etc. The applications of microSD cards include the following.

  • Data Loggers
  • Storage of Audio, Video
  • Visualization
  • Memory is Expandable

Thus, this is all about an overview of micro SD cards. From the above information, we can finally conclude that these types of memory cards are smaller in size than normal SD cards. A miniature variation of the SD card is a microSD card that is used in small electronic devices. A microSD card can be placed with the help of an adapter within any slot of the SD card. These cards are restricted to 1 TB due to their small size, whereas SD memory cards have many high numbers. Here is a question for you, what are the different types of memory cards are available in the market?