"Off-the-Shelf" 200LX used by "Shade Tree Engineer"

I talked to Shannon Jackson from the Jet Propulsion Laboratory about the HP 200LX being used on the space shuttle mission and asked him to explain how he used the palmtop in his job as Senior Engineer. He sent me this response:

To: Wayne

From: Shannon P. Jackson, Senior Engineer Information and Computing Technologies Research Section, Jet Propulsion Laboratory

Yes, they call me a "Senior Engineer Type", but I call myself a "Shade Tree Engineer." I'm always looking for "off-the-shelf" methods to make my job easier. The HP 200LX Palmtop is a good example.

For the ENose, we needed a platform with a good Micro Controller that could connect to many devices, e.g., analog to digital converters, MUXes, Solenoids, an RTC, and an air pump. We needed to control all of these gadgets with one device. We also needed something that was small and light weight. Above all else we wanted something that we could program with fast high-level code.

The 200LX was perfect. With its DOS based system, we were able to write fast code using a mix of MS C (version 5.1), Quick Basic (version 4.5) and the Lab Windows Libraries (for RS232, graphics, analysis, etc). We also used source code and information from the HP Handbook to design a custom display and to control things like the IR Port and HP interrupts.

The one restriction we had to deal with was that flight rules would not allow us to use any batteries. We were able to fool the HP 200LX into thinking it was always booting for the first time by connecting the positive main battery terminal to the backup battery terminal, through a 1K resistor. This caused the 200LX to boot from the A drive where we kept all our applications.

We also were not allowed to open the ENose box to download data. An additional connector was also a problem with safety and regulations. So, while the wired COM Port was used to interface with the Micro Controller, the IR Port was used to upload and download data through a fire extinguisher hole in the side of the ENose box. We used the Palmtop's built-in Kermit protocol along with a Kermit program in the ENose to make the connection.

Thank you for all of your help,

Shannon Jackson