The SREC contains FAT and an interface to use it, as well as the USB-MSD functionality. The USB-MSD functionality is generally useful for retrieving files later to a PC, rather than having to remove the physical SD card and inserting it into a reader so that the file(s) can be transfered to the PC.
If you use the OpenSDA's virtual COM port and connect at 115k with a terminal emulator you communicate with the interface. Below is a recording of moving to the SD card menu, creating a file, adding some data to it and printing the content.
Project code to save to a file (such as your requirement to store data read by TSI sensors) requires a file to be opened (or created), the data written to it each time something is to be saved and, when finished, the file to be closed (possibly optional). Therefore the application interface is straight-forward.
In my case I built the project with uTasker, which contains everything needed to do these things and configured for your board and tested in its simulator. Since I played around with the FRDM-KL25Z yesterday I also posted some details here: Having fun with the FRDM-K25Z
It took about 10 minutes to configure and test the project and then I could generate the SREC with any of a number of compilers.
Serial number: 00-00
Software version V1.4.004
Device identification: KINETIS
Main menu
===================
1 Configure LAN interface
2 Configure serial interface
3 Go to I/O menu
4 Go to administration menu
5 Go to overview/statistics menu
6 Go to USB menu
7 Go to I2C menu
8 Go to SD-Card disk interface
9 FTP client commands
a CAN commands
help Display menu specific help
quit Leave command mode
8
Disk interface
===================
up go to main menu
info utFAT/card info
dir [path] show directory content
dird [path] show deleted directory content
dirc [path] show corrupted directory content
infof [path] show file info
infod [path] show deleted info
cd [path] change dir. (.. for up)
file [path] new empty file
write [path] test write to file
mkdir new empty dir
rename [from] [to] rename
trunc truncate to [length] [path]
print [path] print file content
del [path] delete file or dir.
format [-16] [label] format (unformatted) disk
re-format [-16] [label] reformat disk!!!!!
sect [hex number] display sector
sectw [hex no.] [patt.] [cnt]
help Display menu specific help
quit Leave command mode
>info
SD-card NO NAME (4124049408 bytes) SDHC
Bytes per sector: 512
Cluster size: 4096
Directory base: 0x00000002
FAT start: 0x0000043b
FAT size: 0x00001e02
Number of FATs: 2
LBA: 0x0000403f
Total clusters: 0x000f00f8
Info sect: 0x00000040
Free clusters: 0x000ec7fd
Next free: 0x00001184
CSD: 0x40 0x0e 0x00 0x32 0x5b 0x59 0x00 0x00 0x1e 0xb9 0x7f 0x80 0x0a 0x40 0x00
0xc7
>dir
Directory D:\
---A 03.11.2013 22:35 1370 cache.manifest
---- 03.11.2013 22:35 <DIR> Run
---- 14.01.2014 14:27 <DIR> setup
---- 17.01.2014 02:05 <DIR> utFAT
---A 17.01.2014 01:16 80700 software3.bin
---A 18.01.2014 03:19 80684 software.bin
---- 07.03.2014 01:52 <DIR> test
4 files with 263455 bytes
4 directories, 3967799296 bytes free
D:\>
D:\>file myFile.txt
D:\>write myFile.txt
New file length = 256
D:\>print myFile.txt
UUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUU
UUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUU
UUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUU
UUUUUUUUUUUUUUUU
D:\>dir
Directory D:\
---A 03.11.2013 22:35 1370 cache.manifest
---- 03.11.2013 22:35 <DIR> Run
---- 14.01.2014 14:27 <DIR> setup
---- 17.01.2014 02:05 <DIR> utFAT
---A 03.11.2013 22:35 256 myFile.txt
---A 17.01.2014 01:16 80700 software3.bin
---A 18.01.2014 03:19 80684 software.bin
---- 07.03.2014 01:52 <DIR> test
5 files with 263711 bytes
4 directories, 3967795200 bytes free
D:\>