I'm looking for an internship starting in march 2004. Information about the internship and my short profile.


Ich suche einen Praktikumsplätz für das zweite Praxissemester Informatik ab März 2004. Informationen zum Praktikum und mein Kurzprofil.


project summary page (you find more documentation in the mytemp-doc package)
mytemp-announce and mytemp-users mailing lists (every user should subscribe to the mytemp-announce list, because I will post news about myTemp there)
Pictures of the Hardware

History and News

20.12.2003 Bugfix in the schematics, concerning the connection of the DS1820
15.12.2003 Version 3.10 released, now runs on PalmOS 5 devices.
14.12.2003 I set up the mailing list mytemp-announce.
14.12.2003 this is a screenshot of the actual work in progress version 4. You can download it via CVS.
screenshot of myTemp 4
10.12.2003 Version 4 is on its way. You have access via cvs on the project's summary site. Currently it may be not very useful but is highly under development.

older news


myTemp is a digital thermometer / temperature logger. It consists of an interface, which converts the signals on the Palm's serial Port to the 1-Wire®-Bus. 1-Wire® is a Bus developed by Dallas Semiconductor®. Dallas manufactures 1-Wire® devices for many different purposes, the digital thermometer DS1820 is one among them. The sensor is either directly wired to the interface or is connected to it throug a 2-wire line. DS1822 and DS18B20 are also supported. According to Dallas Semiconductor® the 1-Wire® Bus can be as long as 100m (300ft) and you can attach up to 150 sensors to the bus. (I did not verify this.) Version 3a9 of the myTemp software supports up to ten sensors. Future versions may support even more.


The software is published under the GNU Public License, GPL. The myTemp software contains the 1-Wire® drivers, drivers for the DS18x2x temperature sensors and the user interface as well as the capability to read and write the database of logged values. You can download the zip-archiv from the project's page. There is also a demo version in the zip-archiv. (myTempDemo.prc) that generates random temperature values and thus does not need any additional hardware.


Sourcecode is also included in the zip-archiv. To build the software yourself you need the prc-tools.


You can build the interface either with conventional (wired) parts or in SMD. Since there are no active components in the interface, the Palm's battery can power the interface and no additional battery is needed. Care has been taken during development of hard- and software to reduce current as far as possible, to not stress the Palm's power supply too much. While SMD has the advantage of small weight and outline as well as robustness against mechanical influences, conventional parts are easier to obtain and solder.

Technical Data

Duration of Measurement<5sec
Temperature Range-55 - +70°C
Accuracy+/-0.5%at 0°C-70°C
Current Consumption1,5mAduring the measurement

To connect the interface to the Palm you can either use a HotSync plug or a common male Sub-D 9 serial connecctor, you can connect to your HotSync® cable or cradle. Besides this you can use a gender changer (male/female) to connect the Sub-D 9 plug to your PC running myTemp inside the Palm emulator POSE. You can also use Brian Lane's digitemp.

Connectors for PDAs are available in Germany at Carsten Kurz, Audio Visual Systems or at Handy-Online.

Brian Lane built digitemp, which is an 1-Wire® application for Linux®/Unix®.



Diode D1 is used to limit the voltage on ow-Data to 3.9V. When available you should us +3Vcc on Palm's Pin 2 instead of DTR. In this case you can omit D1.

The DS18S20 needs to have Vdd (Pin3) tied to GND (Pin1), if you are using "parasite power" like in the myTemp interface. Since the cradle does not provide the +3.3Vcc line, you will have to use DTR instead if you want to connect via cradle or HotSync® cable.

Have a look at the schemes for different connections on the schemes page.


Read Dallas application note 74 and the DS1820 datasheet for further information. Both are available on the Dallas Semiconductor webpage.

Information about the handheld's serial port can be obtained at Palmsource®.


Partlist for the conventionally wired parts

R1Resistor 1,5k, > 0.25W18 00 68-08-,25MELF 1k5
D1Zener-Diode 3,9V, > 0.1W1N5228, ZPD 3,9V18 00 68-33-,20MMBZ5228B
D2Zener-Diode 6,2V, > 0.1W1N5234, ZPD 6,2V18 01 14-33-,20MMBZ5234B
D3, D4Schottky-Diode1N5818, ERA-82-004, SB13016 48 28-33-,51MBRS130LT3
U1Digital ThermometerDS182017 61 68-336,11
X1Sub-D Connector9-pin, male74 20 66-08-,96
The Schottky Diodes I used (1N5818) are not on stock at Conrad. I got them from my local electronic dealer. The SB130 should work also. If someone can prove that, please give me some feedback.


Version 3 is finished and was used since 2000 by several poeple around the world. I'm working on version 4, which will be a complete rewrite of the user interface and will include some features that were in the chain for a long time. These are:


PalmOS® 3.0 or greater (a version with some minor functional restrictions for PalmOS® 2.0 is available) I tested PalmOS® 5.0 in the Simulator and it worked - I heard of poeple having problems with 5.0 and also heard that it worked for some others. Handspring® uses a non-standard serial interface, that means myTemp won't work with Handspring PDAs. Please refer to the pdf-Documents on the project status page for information about support for models from other manufacturers.


If you have any questions or suggestions, please subscribe to the mytemp-users mailing list. I will post information about bugs, fixes, updates and new releases on the mytemp-announce mailing list, so I think it's a good idea for every user to subscribe to that list. It's very low traffic. I apologize for the inconvenience you have to subscribe to a list, to get your questions answered, but otherwise I have to answer the same questions over and over again. If you have problems with the lists or problems posing your question or suggestion in english language, you can send eMail to my personal eMail account in german or english language: