Sd Memory Card - Libelium Waspmote Technical Manual

SD memory card

26. SD memory card
Waspmote has external storage support such as SD (Secure Digital) cards. These micro-SD cards are used
specifically to reduce board space to the minimum.
Note: Until February 2018, 2 GB SD cards were distributed; they operated with FAT16. Since that moment, Libelium
distributes FAT32 micro SD cards (8 GB cards from February; 16 GB cards from June). These cards need the bootloader
#J to work properly.
Micro-SD card
Waspmote uses the FAT32 file system. The information that Waspmote stores in files on the SD can be accessed
from different operating systems such as Linux, Windows or Mac-OS.
Figure: SD card slot
To communicate with the SD module we use the SPI bus. This bus is a communication standard used to transfer
information between electronic devices which accept clock regulated bit flow.
The SD card is powered through a digital pin from the microcontroller. It is not therefore necessary to use a
switch to cut the power, putting a low pin value is enough to set the SD consumption to 0 μA.
For example, to get an idea of the capacity of information that can be stored in a 16 GB card, simply divide its size
by the average for what a sensor frame in Waspmote usually occupies (approx. 100 bytes):
16 GB/100 B = 160 million measurements
The limit in files and directories creation per level is 256 files per directory and up to 256 sub-directories in each
directory. There is no limit in the number of nested levels.
Related API libraries: WaspSD.h, WaspSD.cpp
All information about their programming and operation can be found in the SD Card Programming Guide.
All the documentation is located in the Development section in the Libelium website.
Note: Make sure Waspmote is switched off before inserting or removing the SD card. Otherwise, the SD card could be
damaged.
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