Tiny (Mother/Daughter)Board for DIMM-PC®/520-IE Part II

In part one I wrote about the Specs. of the used DimmPC hardware. Because of that this kind of hardware needs some sort of motherboard to operate I designed, with one of our students Zvonimir C., a daughter respectively motherboard for the DimmPCs.

We wanted to used the -IE and the -USB versions with one Daughterboard. The operation purpose should involve longterm logging of various data sources with Ethernet, RS232 or USB interfaces like GPS localization data, ambience data, energy consumption data, operational data from small water power plants ….

Since the used DimmPcs are also equip with a 44-pin mini-IDE interface we have plenty of space for log data. (For example we use the Flash Modules from Transcend).

The Daughterboard should also be selectively powered with 24V or 5V.


For data transfer we use a USB Samba75 Quad Band GSM/GPRS/EDGE modem from Falcom.


We have also a special version with external i²C and SPI interface connectors.

Daughterboard Top up

Daughterboard bottom up

Mobile Apps iPhone/Android project Part I

A new Project raised behind the horizon. Since two months the student Daniel L. and myself are working on an iPhone App for our students.

The Name is secret (for now) so I call it” The APP.” 🙂

Currently we have more or less finished with the application design and now we have started with the implementation of  the first prototype. As the mobile part heavily depends on remote data we also needed a Backend for the core data distribution. Daniel is currently working on the implementation of the iPhone part, and I’m working on the server Backend.

We needed some kind of webservice infrastructure to get the data to/from the mobile application. I have chosen Tomcat for our Server infrastructure, maybe with Apache as first responder. The used framework for the stuff behind is Restlet. The Backend is designed to response with XML or JSON  plain/gzipped  data formats, depending on the received Accept Headers.

Representational State Transfer ( Rest )  is build around around the transfer of “representations” of “resources”. A resource is mostly an URI endpoint if we use HTTP.  Compared to SOAP RPC every developer has to design and implement his own set of functions which represent the interaction interface between the web. App. and the backend. Rest uses the existing HTTP “methods” GET, POST, PUT, DELETE as the command interface. Really cool 🙂 Rest responses are not limited to HTML one can use XML, JSON, binary…

more to come…

have fun

SCALA Final User Commission Metting

The last days my co-worker Marvin and myself went to Antwerp  to meet our Belgium project partners for the final user commission meeting. This meeting marks the end of the EraSME SCALA project.

CUAS SCALA MedIT Dream Team:

  • Matthias Haselberger, Project Leading 🙂
  • Marvin D. Hoffland, International Coordination
  • Mario Wehr, Hard&Software implementation

The SCALA (System Convergence in Applications of Location Awareness)  project was started 2 years ago and ended this month. Our part in the project was to bring a ZigBee based indoor location system into service and implement it into the SCALA  framework. The core framework was designed and implemented by our Belgium colleagues at the university college of Antwerp (Artesis). A major part of the work was done by one of the key researches  Jerry Bracke. (Jerry thx for your hard work 🙂 ).

The user commission meeting was hold at the harbor of Antwerp and  involves several presentations of the participating universities and companies, also a live demonstration of the SCALA middleware layer was shown.

To get some impressions of the meeting check out the attached image album.

If you are interested into the SCALA project, or want to do some projects in context of Location awareness with ourselves or one of our partners please do not hesitate to contact me.

And the best,……The SCALA middleware layer is open source! 🙂

have fun

Campus Door System v3.1 – an access system for education facilities


Since 2013 CDS 3.1 became Open Source, all source code and pcb layouts are available under the Creative Commons (CC) license.
One of the bigger projects I did the last years (starting 2004) was the CDS (Campus Door System) project. The goal of the project was to build access system mainly focused to the needs of education facilities. The system is designed to work with every RFID reader which can be interfaced via serial protocols. Mostly RS-485 is used because it can be used effectively over long distances and in electrically noisy environments.

Strictly speaking the first prototype of the CDS with raw access control functionality was developed by a student (Christian E. with project lead Helmut W.) – he programmed the first core micro controller functionality.

The new system should be build up from scratch with an new designed PCB (Printed circuit board) which hosts the four main parts of the access system:

  1. The Rs485 bus interface
  2. The MultiUART (FPGA)
  3. The C167CR (access control and RFID reader manager)
  4. The embedded system for managing the whole system

1. The Rs485 bus interface:

The newest version of the CDS  v3.x has 16 separate RS-485 bus interfaces and the number of RFID readers is only limited to the used baud rates and because of that the maximum allowed pooling intervals. Version 2.x which is mainly in service has only 8 interfaces.

The bus interface is galvanically isolated from the logic part of the PCB. The RS485 transceivers are  mounted through IC sockets.

2. The MultiUART:

Since I use devices with serial protocols I needed an UART (Universal asynchronous receiver/transmitter) and in that case I needed 8 respectively 16. The  MultiUART should be interfaced through the used micro controllers external data bus. In my case I took the Infineon C167  the battleship amongst the micro controller family.

I learned very fast that digital design for FPGA could be very challenging – even if you have some sort of asynchronous circuit design. Then you have to deal for example with metastability and other nice stuff concerning signal runtimes 🙂  At that time I was a completely rookie concerning FPGA stuff.  I was lucky enough to have a colleague who told me the common mistakes which you could make with FPGA designed. Thanks to Hermann Sterner – you saved me a couple of months 🙂

In the end I got a stable design with 16 UART designs, every UART could be configured independently. That means for every request to a serial slave the system could set the needed baud rate on the fly. Every UART has a 1024 Byte TX FIFO and a 128 BYTE RX FIFO.

Every UART internally communicates with an Interrupt Controller which notifies the micro controller of new RX events.

Every UART is mapped to an certain location in the higher address space.

3. The access controller (Infineon C167CR)

As I already mentioned before I used the C167 for the real-time part. The used C167CR module comes from pytec. With 2MB RAM and 2MB Flash this module has plenty of space for the access tables.

The code which runs on this micro controller is based on the preliminary work of Christian E., the student which developed the first system. In the process of developing I rewrote or adopted a huge part of the code but some parts are still unchanged from the old system and are still in productive use.

The newest version of the access controller is capable to communicate with devices via different protocols and different baud rates. Because of that the protocol stack  for the RFID readers is designed modular. The system can easily be adopted for new protocols.

Firmware updates are done through the embedded system (Web interface). At version 3.x the update process does not need a down time for the system. After successfully downloading the firmware to the flash the system switches seamless to the new program code (switch time >100ms).

4. The embedded system (Web interface, internal database, …)

The whole access system can be administered through a web interface. The used embedded system is the DIMM-PC®/520-IE. I wrote some details about  in one of my last posts. As this system only has 32MB RAM and 32MB FLASH I needed an OS which is highly customizable. -> GNU/Linux is the OS of choice 🙂 .



The core elements I used are:

  • Apache 1.3.x (build-in opcode cache) size < 900kB
  • PHP 3.5.x
  • openSSL (minimal cipher suit) size <1MB
  • Busybox
  • Linux Kernel 2.6.1x special patch set and configuration < 800kb
  • uclibc 0.9.x
  • sqlite 3.x
  • MySQL 5.1.x size <1MB (Community Edition)

BSP ptxdist powered, for DimmPC (AMD Elan) optimized, Build/Toolchain  ready to download.

This part was the most interesting one. Due to the fact that I could not find commercial tools for building embedded GNU/linux OS which suit my needs,  I began using open source tools (ptxdist) and build my own toolchains. I learned how to build optimized cross compile toolchains for the used CPUs  and in the end I got a highly flexible tool/buildchain for building  a whole GNU/Linux with bootloader and all the small things which make the system running 🙂

The embedded system is the core device for administration. Every aspect of the system can be configured through the WEB. All HTTP connections are secured via SSL. The embedded system is holding all persons with there tags, all access rights, all doors respective the RFID readers wired together with access rights in a database system.

The backend of the WEB-Frontend consists of a completely self-written tiny CMS system. Focused to have a very low  memory footprint and CPU resources. The initial design of the CDS Web frontend /backend was done by Georg Gut 🙂 thx – well done.

We are using a special patched PHP 3.5.x running one a patched (tuned) apache 1.3.x to get good performance results. with our CMS system.

On every change on the access data the system generates the access tables for the micro-controller system and updates the tables through the SPI interface.

The version before I used the parallel port for transmitting data between DimmPc and micro-controller. But it turns out that this interface was not stable enough, so I decided to change this interface to SPI with 1Mb/s transfer mode.

Feature List:

  • 16x RS485 bus interfaces, number of readers only limited to selected baudrates (poll times).
  • Multiple readers vendors on one bus segment.
  • Manage person rights
  • Manage person-groups
  • Manage doors
  • Manage door-groups
  • Manage access rights between person/person-groups and doors/door-groups
    • All rights can be time limited.
  • RealTime View of all door actions (door status, last action, last person), AJAX driven
    • Manually open/close door leafs through the WEB interface
  • Automatically door/groups open/close actions at a certain time.
  • Holidays
    • Temporally overrule of  access rights (student groups for example) on holidays.
  • Log Facility
    • Access log WEB frontend
    • System user action/access/view logging
    • Door log,  reader and separate door leaf actions
      • Detailed per person logging
      • Detailed per door/object logging
      • Person/object statistics
  • System Management
    • Select the use of an internal or external database
    • NTP server configuration
    • Log history length
    • Internal database backup/restore
    • Web interface user rights administration
    • LDAP /AD User Authentification
  • System Clustering
    • Up to 4 separate CDS can be administered from one master system.
    • The Web interface exposes an API for third party application to hook into the CDS system.
  • FTP access table upload
    • The access table can also be uploaded through FTP from third party applications.
  • Notifications
    • Set Notification handlers on User/Door actions.
    • Get Emails on definable events. For example on door actions between a defined time period.
  • Smartphone ready GUI, special version for IPad/Android tablets

Check out the gallery for some impressions about the System.

Systems in service: