LinuxJournal has published a story about DSP Linux. Entitled “uClinux as an Embedded OS on a DSP,” the story looks at the differences between Linux and uClinux, uClinux development on an ADI BlackFin DSP processor, DSP limitations and advantages, uClinux's real-time capabilities, and more.

uClinux ports to DSPs began surfacing last fall, when Softier announced a real-time “Media Linux” port to a Texas Instruments DSP chip. Shortly after, Metrowerks let it be known that it had previously ported uClinux to ADI's Blackfin DSP.

At the same time that some DSPs are gaining general-purpose RISC-like instructions enabling them to run actual operating systems, many general purpose embedded processors are integrating media accelerators that enable them to perform DSP-like functions.

According to authors Michael Hennerich and Juergen Hennerich, MMU-less processors such as ADI's Blackfin DSPs use less power and cost less than more complex chips. However, they do not support real memory protection, the “fork” system call, nor complex memory allocation, among other differences. Despite the limitations of MMU-less chips, most Linux applications can be recompiled relatively easily to run on uClinux, the version of Linux for MMU-less chips.

The authors discuss developing with Blackfin uClinux in conjunction with hardware such as ADI's EZ-KIT Lite (Blackfin dev board) or the cool-looking DSP-STAMP. This involves using a graphical kernel configuration tool, setting up busybox, and flashing the kernel and a RAM disk filesystem onto the target hardware. A serial or network-enabled bootloader is then set up. The authors suggest using VisualDSP++ to flash the bootloader — rather than downloading the bootloader via JTAG — because it affords debugging and other capabilities. After that, application development and debugging begins.

Next, the authors explain why hard real-time requirements are generally not needed in embedded multimedia processing systems based on uClinux, before looking at some specific advantages afforded by uClinux on Blackfin.

Read full story at LinuxJournal.com

 
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