Optimizing hard disk and compact flash performance in Linux Embedded Systems

Compact flash are often used in Digital Signage applications and hard-disks used in both signage application and IP set-top-box to play high definition videos. However, sometimes the performance of those devices and the performance limitations of embedded systems may make the task difficult especially for higher bit-rate videos. Choosing the right file system Once of the easiest way to improve performance is to select an appropriate file system. The best performance is achieved by ext-2, followed by ext-3, fat 32 and ntfs on the embedded system I worked with at least (e.g. Sigma Designs EM8620 and  SMP8630 series).  Basically, if your CF card/HDD is not supposed to be taken out of your device, then ext-2 is the obvious choice. However, if your user for whatever reasons need to take the devie out and connect it to a Windows PC FAT 32 or NTFS might be a better choice, although it […]

NTFS for Embedded Linux Systems

NTFS benchmarchs for embedded systems Tuxera vs NTFS-3G vs ext-3

Since now more and more HD videos are larger than 4GB they can not be stored into FAT32 file system, and require the use of other file systems, the most popular being ext2/ext3 or NTFS. However, since many users may want to access the mass storage devices (IDE / SATA harddisk, USB Harddisk, USB Thumbdrives…) in Windows as well as in their embedded systems (IP STV, Digital Signage..) NTFS seems to the best choice to share data between Windows systems and embedded systems using Linux. NTFS is available in the Linux kernel. However only read-only is fully supported and the performance is about 25% less than ext-2 or ext-3 for the platforms we tested (EM8623L and SMP8635), but this is still acceptable to play most of HD Videos. However, if the device also needs to download videos from a server or other P2P clients, having a read-only file system will […]

Finding and fixing memoy leaks in your software

Memory leak

Memory leaks will cause your device to crash after a period of time once it runs out of memory. A quick way to find out if your application has a memory leak(s) is to monitor it with top:

If you see the %MEM increase over time for no particular reason, then you’ve got a memory leak. However, it might be tricky to isolate where the issue occurs exactly. The first thing to do is the review your source code for the following: Malloced memory is always freed fopen is always followed by fclose, and open by close scandir calls are properly freed Threads are properly terminated with pthread_cancel & pthread_join or pthread_detach, etc… If after a code review you cannot find the reason for the memory leak, use the following piece of code:

  The memory usage is displayed in numbers of pages. Usually, one page is 4096 […]

Reducing truetype font file size for embedded systems

Embedded systems often have limited memory, that can be a challenge when your application requires Asian languages where fonts might be several megabytes large. Below we describe a method to reduce the file size with Fontforge using simhei.ttf, a CJK font as an example. Fontforge Fontforge is an open source font editor running under Linux and Windows/Cygwin. For the latest version see http://fontforge.sourceforge.net/ Reducing Font Size Removing Bitmap from Font File. Some TrueType files embed a bitmap version of the font. When Fontforge opens such a file, it will ask whether to keep the bitmap or not. We can remove the bitmap to reduce the file size. Using a glyphs subset adapted to your application. We can use Fontforge with cidmap (Fontforge proprietary) and/or Cmap (from adobe) to perform this task. Please check http://partners.adobe.com/public/developer/font/index.html#ckf for further information on CJK/CID file for your language. In our example (simhei.ttf), which can be […]

Mounting a JFFS2 image in a Linux PC

We often use JFFS2 binary images for embedded system, generating them with mkfs.jffs2. In some instances, it could also be good to mount a jffs2 image into your PC to modify it directly. To do that,  type the following commands as root in a linux shell: modprobe mtdcore modprobe jffs2 modprobe mtdram modprobe mtdchar modprobe mtdblock dd if=image-jffs2 of=/dev/mtd0 mount /dev/mtdblock0 mnt If your image is larger than the default kernel size (4MB in my case), you can try to adjust the mtdram device size with the total_size parameters. when inserting the mtdram module, e.g.: modprobe mtdram total_size=8096 where total_size is expressed in KB Further details can be found @ http://www.handhelds.org/hypermail/familiar/62/6232.html Jean-Luc Aufranc (CNXSoft)Jean-Luc started CNX Software in 2010 as a part-time endeavor, before quitting his job as a software engineering manager, and starting to write daily news, and reviews full time later in 2011. www.cnx-software.com

Resizing an NTFS partition with Linux

If you have a computer where you already installed Windows and you wish to install Linux as well (dual boot), you may want to resize the NTFS partition to get more space for the Linux partitions. One way it to use Gparted (Gnome Partition Editor) – http://gparted.sourceforge.net/ with a boot CD. Here are the instructions: •  Boot from the CD •  Hit <ENTER> when you see the message “Boot:”. •  Select language, keyboard and screen resolution from the menus. •  The partitioner should start and the following steps are intuitive More details are available @ http://mlf.linux.rulez.org/mlf/ezaz/ntfsresize.html#example It is also possible to do it with a USB Thumdrive if you do not want to burn a CD and your bios can support booting from a USB device. http://gparted.sourceforge.net/liveusb.php Jean-Luc Aufranc (CNXSoft)Jean-Luc started CNX Software in 2010 as a part-time endeavor, before quitting his job as a software engineering manager, and starting […]

Sigma Designs EM862X Resources

We are using EM8623 for the development of set-top-box and digital signage applications. In order to develop for that platform, an SDK must be purchased directly from Sigma Designs. However, the linux kernel is open source so companies need to release the source if they modified it in their products. For example, you could download the GPL source released by Kiss Technology – http://www.kiss-technology.com/files/firmware/GPL.zip. This is only the GPL source for your reference, after that there are also sigma linux drivers (not released by sigma) and not GPL, and the MRUA package that needs to be purchased from Sigma Designs. One the challenge of using EM862X platforms (EM8620L, EM8621L, EM8622L, EM8623L etc..) is that it has no MMU (Memory Management Unit) and that may make the software debugging very interesting.. You may experience spectacular crashes, kernel panic without any apparent reason. But most of the time this is due to […]

Software Development Cycle Tools

In order to manage software development with a small team, we use the following tools: Version control software: e.g. CVS, Subversion, git… Bug tracking software: e.g. Bugzilla Nightly build scripts or continuous integration software: e.g. CCNet For our linux based projects (embedded software), we use CVS, Bugzilla and nightly build scripts (with crontab) For our Windows-based projects (.NET Framework), we use CVS, Bugzilla and CCNet. Jean-Luc Aufranc (CNXSoft)Jean-Luc started CNX Software in 2010 as a part-time endeavor, before quitting his job as a software engineering manager, and starting to write daily news, and reviews full time later in 2011. www.cnx-software.com