CCilot XA and CCpilot XS
Product revision: 0.12
Software guide
2018-03-19
www.crosscontrol.com
9
4.
Accessing and using the interfaces
This section covers basic usage and access of the device hardware. Most of the hardware is accessed
using the default Linux interfaces but some device specific interfaces may require additional
software and/or interfaces to be accessed. See the
CCpilot XA and CCpilot XS– Programmers
guide
documentation for general information regarding software development using the devices
interfaces.
Depending on product model, all interfaces may not be present on your specific model. There may
also be additional methods to access the device than the ones described herein, depending on
operating system and additional installed software.
4.1.
SD file storage
The device uses Secure Digital flash card based storage, i.e. SD card. The storage is identified to the
system as a block disk device.
The Secure Digital flash card is industrial grade classified and has both static and dynamic wear
levelling to prevent a premature aging and to ensure the longest lifetime. Still Secure Digital flash
cards have a limited number of write cycles. It is recommended that the amounts of writing to
storage are limited within the application. Rather keep information in RAM memory and write
larger blocks at one time instead of frequently writing smaller pieces.
There’s though a trade-off that an application needs to make here, if the data to be saved is mission
critical or not. An application shouldn’t cache files on the SD card, since in case of a sudden power
loss, the SD card’s writable partition is made write-protected to protect the files from being
corrupted due to the power loss. An application needs to be careful when writing large files, as it
can cause pro-longed write-protect sequences, which is a potential hazard to the file system and SD
card.
Additional details about SD card usage recommendations can be found in
CCpilot XA and CCpilot
XS – Programmers guide.
4.1.1.
File system layout
In Linux, the Secure Digital flash card is partitioned into two root file system, which are write
protected, and one user file system area, which is write enabled by default. The latter area is the
preferred location for user software installations. See chapter 7.1 Installing new drivers,
applications and system packages.
The two initial partitions hold each operating system mode’s root file systems, i.e. first the rescue
system root file system and second the main system root file system. The root file system is located
in the SD flash card. It is of type EXT4 and it is mounted as read-only for security reasons. It is
mounted by the kernel boot-up sequence.
Any attached USB memory is automatically mounted once inserted. Supported formats for USB-
memory include FAT types which is the default format for USB-memories. USB-memory devices
are never automatically formatted so if file system is unsupported, device is just not mounted.
Mount point
Mount status
Media
/
Read only
SD card, second partition
/usr/local
Read-write
SD card, third partition
/media/usb
Read-write
USB memory, if available
/media/usb2
Read-write
Second USB memory, if available
