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1070_0_Product_Manual - October 28, 2010 8:52 AM
Technical
Power Over Ethernet
Power over Ethernet can be used to provide both a network connection and power to a device when a power outlet
is not available. This means that with the proper adapters, you can run the PhidgetSBC entirely off an Ethernet
source. The PhidgetSBC does not draw power directly from a powered Ethernet line, but instead can use a setup
where the power is split to a separate line again near the PhidgetSBC. The board has been tested and will work with
Power Sourcing Equipment that can output 6-12VDC.
Hardware Layout
The PhidgetSBC is based around the SC32410 processor. This is an ARM-920T based microprocessor from Samsung,
which runs at 266MHz. Connected to this is 64 MB of SDRAM, 64 MB of small page NAND and a 10/100baseT
Ethernet controller. The microprocessor brings out 2 USB full-speed ports, one of which is connected to the
embedded Interface Kit 8/8/8 and the other which is connected to a 4-port USB Hub chip.
Software Layout
The PhidgetSBC runs a custom Linux Distro as its operating system and gets booted with U-Boot. The kernel is 2.6.x
and generally kept up to date with the latest releases. The root filesystem is created using Buildroot and is mounted
in a 50MB nand partition using the JFFS2 filesystem, in Read-Only mode.
There is 5.5MB userspace partition, also using JFFS2, which is mounted as Read-Write. This is mounted at /mnt/
userspace.
The system comes with pre-created users ‘root’ and ‘user’. Their home directories are located in userspace and
sylinked into /home/user and /root
Configuration data is located at ‘/mnt/userspace/.config’. This is where all configuration that can be set through the
website is located.
User applications are stored in ‘/mnt/userspace/userapps’, each is their own directory.
Changes to the root filesystem can be made by re-mounting the root filesystem in read-write mode with the
command: ‘mount -o remount,rw /’. This is important if you wish to add your own libraries or kernel modules. Note
that any changed to the root filesystem will be overwritten if a system upgrade is performed.
The /var directory is located in /tmp, which is mounted as a ramdisk. This means that anything written to /tmp
or /var will be gone on the next reboot. This includes system logfiles. /tmp is a good place to write out data that
doesn’t matter (stdout, logfiles, etc.) because it doesn’t fill up or wear out the NAND flash. If you want to write out
important data, write to userspace, or alternatively, attach a USB flash drive and write to it.
Date and Time
The date and time are set using ntp (network time protocol) at boot. If the PhidgetSBC is not connected to the
internet, it will not have the correct time because there is no on-board battery to keep a real-time clock. If the ntp
daemon fails to set the time, it is set by default to 00:00:01, 01/01/2000. The ntp daemon continues to run in the
background and will periodically update the clock, keeping it very close to real time.
The timezone is stored in ‘/etc/TZ’. This timezone affects how the date / time is printed. The timezone can be
configured using the website configuration in ‘system: settings’.
