Oct, 2007
by Cliff Brake
Welcome to the Embedded Perspective Newsletter, a free monthly newsletter providing insights, reviews, and perspective on Embedded Systems development and related industries.
Feedback is appreciated. Email me at: cbrake@bec-systems.com.
For back issues or to subscribe, visit: http://bec-systems.com/web/content/view/39/35/ . These articles also appear on the BEC Systems web site and are available in an RSS feed. Please forward this to anyone you think might be interested.
In this issue:
* The correct way to add packages to an OpenEmbedded Image
* The Embedded WiFi module Quest
* How to implement realtime periodic tasks in Linux applications
* Mono support in OpenEmbedded and Openmoko packages
* Compulab cm-x270 NAND flash eraseblock sizes
* Howto load Openembedded on the Compulab cm-x270 computer module
* Linux 2.6.23 for the Compulab cm-x270
| The correct way to add packages to an OpenEmbedded Image | |
Update 2007-10-14: use IMAGE_INSTALL in image recipe Update 2007-10-22: a few corrections, added full path for include and comments As more and more OpenMoko developers are coming on-line, it is becoming obvious that my previous post (http://bec-systems.com/web/content/view/59/9/) about adding packages to OpenEmbedded could use some improvements. This post suggested using the DISTRO_EXTRA_RDEPENDS variable, which was intended to only be used in distro.conf files. A better approach is to create a custom image recipe that includes the packages you want. This article covers how to create a custom image recipe. | |
| Read more... | |
| The Embedded WiFi module Quest | |
| How does one implement WiFi functionality in vertical, low volume portable products? This is a good question, and one I've been struggling with for the past 3 months. I have a customer who is designing a portable data acquisition system based on a AT91SAM9260 processor, and needs WiFi functionality. The fundamental problem is that no one has time to deal with low volume customers, and the task of implementing WiFi functionality is obviously complex. At volumes of 5000 units a year or less, it makes a lot of sense to go with a WiFi module rather than trying to integrate the WiFi chipset on the board. This article covers some of the options we have looked at and some of the possible solutions. | |
| Read more... | |
| How to implement realtime periodic tasks in Linux applications | |
| Have you ever wondered what is the best way to implement periodic tasks in Linux applications -- something better than usleep()? This article covers a number of issues related to this subject including real-time tasks, the different timers available, timer resolution, and how to implement periodic tasks accurately so that error is not accumulated. The recent inclusion of the high-resolution timers in the mainstream kernel makes this a very interesting subject. | |
| Read more... | |
| Mono support in OpenEmbedded and Openmoko packages | |
As of today, the Mono build in OpenEmbedded is working pretty well. Mono support for ARM and other embedded architectures should add some interesting capabilities for embedded Linux devices. Having written a number of large embedded Linux applications, I can really appreciate the advantages of high level languages for exception handling. It is also interesting to note that Java support in OpenEmbedded is making progress as well (http://jalimo.org/wiki/doku.php). Windows CE developers have already taken to the .net compact framework in a big way, so its nice to see similar capabilities for embedded Linux systems. A feed has been set up for installing mono packages on your Openmoko phone. Add the following line to a /etc/ipkg/*-feed.conf file: src/gz mono-armv4t http://dev.bec-systems.com/feed/openmoko/mono And then: ipkg update ipkg install mono The packaging is fairly granular, so look at the listing in the above URL to see a complete list of what is available.
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| Compulab cm-x270 NAND flash eraseblock sizes | |
If you are having trouble mounting a JFFS2 file system on a Compulab cm-x270 module, you may have a device that has a NAND flash with 16KiB eraseblocks. All of the devices I have personally used to date have had 128KiB eraseblocks, but I just helped a cm-x270 user through some flash issues and after much pain discovered the eraseblock size was 16KiB on his module. A variable has been added to the cm-x270.conf file in OE to set the eraseblock size that can be overridden in your local.conf file if you are using OpenEmbedded to generate jffs2 images: http://www.openembedded.org/repo/org.openembedded.dev/conf/machine/cm-x270.conf
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| Read more... | |
| Howto load Openembedded on the Compulab cm-x270 computer module | |
| There are quite a few people using (or would like to use) OpenEmbedded on the Compulab cm-x270. The cm-x270 is a high performance, low cost computer module that can be used with a custom baseboard in embedded systems (see http://bec-systems.com/web/content/view/62/9/ for a review). I get a lot of questions on how to load OpenEmbedded on this system, so this howto attempts to detail a procedure that can be used to load OpenEmbedded. | |
| Read more... | |
| Linux 2.6.23 for the Compulab cm-x270 | |
Updated 2.6.23 kernel patches for the Compulab cm-x270 are now available in OpenEmbedded: http://www.openembedded.org/filebrowser/org.openembedded.dev/packages/linux/linux-2.6.23/cm-x270 The cm-x270 support in OpenEmbedded has undergone a lot of clean-up in recent weeks. Now is a good time to give OpenEmbedded a try if you need a full featured Linux distribution for the cm-x270.
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