The uCsimm kit

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Hardware

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Frédéric has an engineering degree in electronics and is involved in product design and application PCB at a medium sized company based in the outskirts of Bordeaux.

Abstract:

At the last ABUL LINUX party, I briefly introduced the uCsimm Kit to some people. Considering the growing interest in this subject, I decided to write this article. Kit pictures and links to related WEB sites are included.

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Linux, an embedded system ?

In the past, LINUX was mostly known by University students and hobbyists Nowadays it is ramping up in the industrial world, more precisely in the little published corner of embarked systems. Although already used by VME cards for some time, LINUX was hardly a viable alternative to more specialized systems such as vxworks, rtems and many more. One of the first successful LINUX applications in embedded system is the WEB Router. For a short while now, PLEB (PAD) or Empeg (MP3 radio car) have been running. Other projects such as RT-LINUX are able to soften the real time constraint for the LINUX core. This is important when used for Digital Signal Processing.

uClinux project

Sometime ago, while surfing the WEB, I discovered uClinux, a project for implementing the LINUX core inside equipments without MMU. Mostly aimed at �C and its applications, implementations were done for 683xx, MPC5xxx from Motorola, i960 from Intel and ARM7TDMI from ARM. The direct consequence of a non-MMU architecture, is the unavailability of the function fork(). uClinux is implementing this missing fork() by using BSD vfork(). In doing so, the missing MMU will hamper the application software size or data protection since the memory space is shared by the tasks. Usually an MMU (Memory Management Unit) is in charge of safguarding program and data space for each process. Without this unit care must be taken by programmers not to write programms that erase themselves or others as they all share the same memory address map. uClinux is based on a 2.0.38 kernel but the other application programs are based upon the REDHAT distribution.

uCsimm kit

The uClinux project is based on the uCsimm product. This Kit looks like a SIMM30 memory bank . You will find a Dragonball 68EZ328 �C on the board. The heart of the system is nothing more than the good old 68000. It is bundled with UART, SPI interface, LCD controller, timer and PWM. The memory is composed of 8 Mb DRAM and 2 Mb Flash EPROM ICs. The controller CS8900 made by CRYSTAL is acting as the RJ45 interface circuitry. The 2 Mb flash memory is for the core software and some of the utility test programs. Among those are a nfs server and a tiny web server. The exact content of the uClinux kit is rather simple and well documented. For those without Linux, a SUSE-5.3 Distribution included with the kit.

uCgardener Kit

This Kit is the base for the uCsimm. It includes a SIMM slot, a 3.3V regulator, coupling capacitors, a DB9 connector for the RS232 port, an RJ45 connector and a customizable wrapping zone.

Related WEB sites

uClinux:

RT-Linux

http://luz.cs.nmt.edu/~rtlinux/

Linux embedded related