Welcome to Jens David's Homepage

This is the homepage of Jens David, DG1KJD.
WAP enabled - also available in WML!

Current/Home Address:

Jens David
Jaegerstr. 25
D-01099 Dresden
Saxony, Germany

+49 163 6 32768 3  (mobile, O2)
+49 351 3201118    (landline, Arcor)

dg1kjd@dg1kjd-svr.ampr.org             (primary now)
dg1kjd@afthd.tu-darmstadt.de           (whenever it works...)
jens.david@jens-david-consulting.com   (job)
DG1KJD@DB0LJ.#RPL.DEU.EU               (DieBox)

Sorry for the simple layout of this page. I try to concentrate on development, not creating fancy web pages. Sorry again, no German version available.

Here are some of my projects and publications (in no particular order) which might be of public interest, feel free to download and distribute all of them, software is usually GPL'ed, hardware descriptions and documentation can be freely distributed. However, there is NO WARRANTY for anything. It might even eat your harddisk, blow up your house or kill your cat.

Linux Kernel AX.25

Here you will find stuff related to Linux Kernel AX.25. In particular patches implementing the AX.25 protocol stack (the protocol stack that comes with the original Linus kernel tree is years old, broken by design and by now fucked beyond repair (FBR) [TM]), some fixes and new device drivers. This patch was previously (until 2.2.19) maintained by me but due to QRL-related issues I don't have time to do this any more.

AO-40 satellite telemetry project

Some stuff developed as part of my diploma thesis. A Ptolemy model of a telemetry demodulator, a KDE2 application which performs the same task and a decoder/viewer for the data. STP and Internet multicast support.

PCISCC-4: Four-port PCI compatible SCC card

These are the official PCISCC-4 information pages including construction data. PCISCC-4 is a four-port PCI compatible SCC (Serial Communication Controller) plugin card for connection of synchronous serial network devices, typically ham-radio modems or WAN transceivers.

Realtek RTL-8139 driver for Linux 2.2

This is a patchset that updates support for Realtek RTL-8139 based local area network interface cards in Linux 2.2. The original driver by Donald Becker is unfortunately quiete unuseable and -readable (not to say broken). The version 0.9.22-2.2 of this driver for Linux-2.2.20 can be downloaded above and applied to the vanilla kernel. Linux-2.2.21 and later do -- as I was told -- NOT include this version, but an older, broken one although this version (with completely reworked TX code) was submitted a couple of times without any reaction. I honestly do not know what is going on, please patch manually.

Ptolemy model of a AO-40 telemetry demodulator

This archive contains a AMSAT-OSCAR 40 (aka Phase-3D) 400bps BPSK telemetry demodulator. A costas-loop downconverter, an AGC galaxy, a symbol timing recovery and sampling galaxy and a decision feedback equalizer star as well as some documentation. Makes nice learning material.

Backstein-TV Professional

This is a project which helps Philips-MediaBox users to watch digital TV (mostly in Germany) without having a subscription card. The hack uses a MicroChip PIC16C84 or PIC16F84 (or a smart card containing these chips respectively). It can only be used with SECA compilant systems, not with the system in use by Premiere/DF1 in Germany. It will not work with encrypted channels either, just free-to-air.

Soundmodem Intern (Paper, German)

This is the paper presented at the 15th International Packet Radio Symposium at Darmstadt Technical University (TUD) about the Linux soundmodem implementation and error correcting codes (ECC). Only German version available.

AIRS - Amateur IP Routing System

Here you will get the current version of AIRS. Note that I will not spend a lot of time maintaining this since kernel AX.25 is a much better aproach. The idea behind AIRS was to create a userland solution for routing IP traffic via ham radio packet radio network, pretty similar to what Win/FlexNet does now. However, AIRS only ran on Linux and OS/2. The OS/2 tree is included but no more maintained. It should still work though.

IRCGATE - a perl script

This is a little perl script which can be used to connect an IRC (Internet Relay Chat) server to a ham-like convers system. The idea behind it is to allow the users to use a standard IRC client for conversation. This is also a nice example of how to use Linux' AX.25 sockets from within a perl script.

SPIProg - a SPI EEPROM Programmer

This is a little programmer for SPI (Serial Periphery Interconnect) EEPROMs such as, but not limited to, Xicor X25640, X25650; Atmel AT25080, AT25160, AT25320 and AT25640. The package includes the software and building instructions for a parallel port programming adapter consisting of a D-sub connector, three resistors, some wire and an IC socket.

CardCrypt - a Cryptographic tool with smartcard support

This is the result from a university project. The task was to write a program which had to run on Windows 95 that enables the user to apply asymetric cryptographic algorithms to data. The keys can be read from disk or a smart card. The program is pretty neat and uses the graphical user interface of windows to present a cool integrated crypto environment to the user. It's a lot of work in there. However, the assignment's idea was stupid (unfortunately I had no influence on that). Maybe it is of interest for somebody else.

An introduction into Field Effect Transistors (Paper, English, stupid)

This is a small paper I had to write for a seminar.

An introduction into the principles of modern soundcards (Paper, German, stupid)

This is a small paper I had to write for another seminar.

DCF-77 decoder

This is the result from a school project on grammar school, years ago. The aim (which was reached) was to write a DCF-77 decoder in Pascal and document it. It might be of interest for those who want to know how DCF-77 works.