December
2005, Issue 185
Browser-Based
Telemetry System
TStik
Let’s
cover the hardware I used on the rig. Being a quadriplegic,
I’m reluctant to breadboard or solder circuits from
scratch. Enough pulling wires with my teeth. I’m happy
to use SBCs instead of the various microcontrollers
I’ve used in the past. Better still, I’d rather not
start each project from scratch and pull out my hair
when dealing with ASM code and segmented memory. Let
the virtual machines do all the dirty work.
There
are numerous virtual machines for popular microcontrollers
like PICs and HC11s. One option is to run Java on Linux
when more horsepower is required. You get more bang
for your buck on the x86 or MIPS platforms, but make
sure that whimsy and price don’t get away on you.
Although
two USB ports on the boards from Technologic Systems
(embeddedx86.com) could have supported cameras on the
rig, I used self-contained network cameras. I didn’t
need a fast chip to process images (see Photo 1).
|
(Click
here to enlarge)
|
Photo
1—The new Airlink modems have an Ethernet interface
instead of PPP over RS-232. This simplifies the
networking for adding network cameras or redundant
controllers. |
Which
sensors and buses must be bridged up to TCP/IP networking?
For this project, I needed Dallas Semiconductor’s 1-Wire
bus, so I used Systronix’s TStik TINI400. The DS80C400-based
TStik is only an 8-bit chip, but it supports 1-Wire,
SPI, I2C, CAN, Ethernet, RS-232, and TTL serial when
slotted into the TILT Pro socket board. The forward-thinking
designers also added a SIMM edge connector, which is
a standard expansion bus for embedded java systems like
the high-powered JStamp and JStik. Unlike the other
devices from Parallax, these are agile processor-based
controllers that run byte codes as native code. This
makes it as easy to prototype and swap out JSimm cards
as building with Legos).
You
don’t need to buy a development kit. Simply connect
to the on-board serial, FTP, and Telnet servers to load
new firmware and your binary code. Then log on to the
Unix-style command prompt to run and debug your programs.
The TStik also has web server capability, including
servlets, but it’s too limited to handle enough requests
to be a proper front end for an Internet telemetry system.
If you’re comfortable with standard Java build tools
such as Ant, you won’t have any trouble getting up and
running.
