What About eMMC Flash Memory? eMMC stands for "Embedded Multimedia Card," which itself grew out of its predecessor, MMC (Multimedia Card). Multimedia cards first hit the shelves back in 1997. They were used as a storage medium for portable devices, including the earliest MP3 players and digital cameras. Ports for the cards were often built into
RS-MMC. In 2004, the Reduced-Size MultiMediaCard ( RS-MMC) was introduced as a smaller form factor of the MMC, with about half the size: 24 mm × 18 mm × 1.4 mm. The RS-MMC uses a simple mechanical adapter to elongate the card so it can be used in any MMC (or SD) slot. RS-MMCs are currently available in sizes up to and including 2 GB.
SPI serial flash is small, low-power flash memory that features a Serial Peripheral Interface (SPI) and pin-for-pin compatibility with industry-standard SPI EEPROM devices. Its small footprint reduces ASIC controller pin count and packaging costs, saves board space and keeps system costs down. Offering Circuit and Interfacing. SD card has a native host interface apart from the SPI mode for communicating with master devices. 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. Since the SPI is a widely used protocol and it is available in most
SD cards internally use SPI flash memory, so the question seems pointless, especially since SD cards and SPI flash memory are available with various speeds. I think that you will have to do your own testing, concentrating on what is important to you.
I will try to answer your questions clearly: - You are indeed limited to 8MHz speed on the normal SPI peripherals. However, the nRF5340 does boast a fourth SPI peripheral with support of 32MHz speeds. - From what I can see this is true. Non of our devices supports 4-bit SD Card interfacing, so I believe this would be difficult to utilize anyway.
The SD card interface can transfer data in a one-, four-, or eight-bit mode at various rates. A SD card can also be accessed using a SPI interface instead of the SD card interface using the same pins of the card. (In fact, without information on how a USB-to-SD card reader actually works, you could assume that the SPI interface might be the
From my experience, typical SD card current consumption is ~30mA in SPI mode and ~100mA in 4-bit SD mode. My advice would be to include the first figure with a 2x or 3x safety margin (that is, 60 or 90 mA) in your device power budget, and make sure that the rest of your circuit never consumes more than 500-60 = 440mA or 500-90 = 410mA
This example shows how to read a file from a SD card using the SD library and send it over the serial port. On the SD card, there is a file named "datalog.txt". In the loop (), the file is opened when calling SD. open (). To send the file serially to a computer, use Serial. print (), reading the contents of the file with SD. read ().
1Mivz.
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    • spi flash vs sd card