3,260
edits
Changes
no edit summary
* Isolate I2C clock from noise sensitive signals
* Avoid stub
==Functional guidelines==
===Sudden power off management===
From the architectural standpoint, modern embedded systems often resemble traditional PCs. For example:
* they implement a rich set of I/O interfaces (large displays, Ethernet ports, USB ports, SDIO sockets etc.)
* they likely run complex operating systems that derive from desktop world (linux, Android, Windows CE etc.)
* they implement complex storage schemes (raw NAND, SSD, eMMC etc.).
One of the main difference between such systems and PCs is that the formers are - if appropriately designed - inherently resilient to sudden power fails (see for example this presentation: [http://events.linuxfoundation.org/slides/2010/linuxcon_japan/linuxcon_jp2010_jung.pdf Application of UBIFS for Embedded Linux Products]).
In any case, system designer should take into account these events and decide if and how manage them explicitly. Here are some typical techniques used to deal with this situation:
* in case the system is used by human operators, the use of clean shutdown - triggered by the user himself - should be encouraged to prevent sudden power off. Technically speaking, this can be done via GUI (soft button) or mechanical device (push buttons and alike). In the latter case, puch button controllers such as [http://www.linear.com/product/LTC2954 Linear LTC2954] can be very useful to implement this feature
* in case no human operators interact with the system, more complex solutions might be required. This strategy is strongly dependent on hardware characteristics of SOM and must be approached on a case-by-case basis.
