IMPORTANT NOTE: While connecting the power supply, make sure that the supply is drawn from a 3.3V supply as a 5V supply would see your card go up in smoke. The CS (chip select) pin should be connected to the corresponding CS pin on the microcontroller or on any digital I/O pin on the microcontroller. The SCK (serial clock) pin should be connected to the SCK (serial clock) pin on the microcontroller.
The MOSI (master out serial in) pin should be connected to the SDO (serial data out) pin on the microcontroller. The MISO (master in serial out) pin should be connected to the SDI (serial data in) pin on the microcontroller. If the logic level of the microcontroller is different than the SD card, level shifter needs to be used for converting the line voltages. But to understand the connections, let us analyze this fairly simple circuit. Most development boards have a dedicated SD card slot. It should be kept in mind that throughout the communication between the two devices, the micro-controller will be sending out the clock. clock, chip select, data in and data out. Once the microcontroller is in the SPI mode, communication between the master and the slave is done via 4 pins viz. The micro-controller sees the SD card as an addressable sector on which read/write functions are possible. The SD cards have a microcontroller that shows their availability to the master controller(microcontroller). Most micro-controllers use the SPI communication protocol to interface with the SD cards. The working voltage range of SD family is 2.7V to 3.6V and this is indicated in the operation condition register (OCR). Since the SPI is a widely used protocol and it is available in most low-cost microcontrollers, the SPI mode is the widely used interface in low cost embedded systems.
The native interface uses four lines for data transfer where the microcontroller has SD card controller module and it needs separate license to use it. SD card has a native host interface apart from the SPI mode for communicating with master devices. To be specific, we will be dealing with the use of SD cards in small embedded systems. What we are going to learn is the use of SD cards in an embedded system. The microSD is the miniaturized SD memory card format with a small form factor and is widely used in various electronic devices. Some of the standard variations include SD, SDHC, SDXC, SD-ultra high speed etc. There are various topics related to the SD card such as the different device families, speed classes, smart cards, card security and so on and it is used in various markets like digital cameras, personal computers, and embedded systems. Therefore, to meet the market requirements, the SDA was set up as a non-profit organization to promote and create SD Card standards. Since its inception back at the start of the century, the demand for this medium-sized, energy and space-efficient, the memory storage device has been growing at a fast rate. Note: It does not come with a microSD card! The 16GB and 32GB microSD card from Raspberry Pi Foundation works great with this card reader/writer.The secure digital card (SD) is a low cost, non-volatile memory card format developed by the SD Card Association. Max read speed is 16 MB/sec, max write speed is 6 MB/sec - most microSD cards are not this fast so the bottleneck will be the card, not the reader. It also has a little plastic cover for the USB A connector part so it won't short against nearby electronics. It comes with a handy little cord so you can attach it to your datalogger project.
No drivers are required, it shows up as a standard 'Mass Storage' device under any OS. This is one of the cutest little microSD card reader/writer - but don't be fooled by its compact size! It's wicked fast and supports up to 128 GB SDHC cards! Simply slide the card into the edge, flip it over and plug it into your computer's USB port. Lithium Ion Rechargeable Battery and Charger.Lead Acid Rechargeable Battery and Charger.