Rationale
Many devices are connected to the Internet
These days, many devices are connected to the Internet.
Some refrigerators are connected to the Internet and the status of the
refrigerators such as temperature, whether the door is open or not,
current stock can be checked through the web browser.
And, there are many telerobots in the Internet these days. A telerobot is
a robot which can be controlled remotely through the network.
And, there is a laundry machine connected to the Internet and the current
status of the machine can be checked remotely.
And, Some people wire their home and control all the appliances in their home
remotely. There is a house where the doorbell is connected to the Internet and
if the doorbell rings, then an email is sent to the owner of the house.
Also, a phone and a caller-ID unit are connected to the Internet and the
owner can check the recent calls throuth the Internet.
There can be many other applications that may need the Internet-connected
devices.
Here are some links to the Internet-connected devices.
- Refrigerators
http://www.hamjudo.com/cgi-bin/refrigerator : Shows the current
status of the refrigerator (temperature, freezer compartment temperature,
the temperature of Coke, door status).
- Laundry machine
http://spleen.mit.edu/LAUNDRY/index.html : Shows the current status
of the laundry machines in the laundry room(whether it is used now or not,
how long it is not in use, when it will be available).
- Robots
http://telerobot.mech.uwa.edu.au/ : Users can move the arm of the robot and
pick and drop an object.
http://KhepOnTheWeb.epfl.ch/ : A small robot in a maze is shown.
User can move the robot and watch it through the camera.
http://www.cs.cmu.edu/~Xavier/ : Users can move the robot in the building
and see through the eye(camera) of the robot.
http://hogwild.hamjudo.com/cgi-bin/wave : Users can wave a simple robot
hand.
- Hottub
http://www.hamjudo.com/cgi-bin/hottub : Shows the temperature of the hottub,
the outside temperature, etc.
- Cameras
http://citynight.com/livecam.html : Users can change the direction of the
camera.
- Sign Board
http://www.weissman.org/sign/ : Makes the Internet user be able to write
some messages on the LED sign board.
- Wired House
http://www.icepick.com/ : Doorbell, fridge, phone, caller ID, bunch of
cameras inside and outside of the house, and barcode trashbin are connected
to the Internet. And, even the toilet flush logs can be retrieved in the
Internet.
How to connect devices to the Internet?
Most of the devices usually supports a very simple communication protocol such
as RS-232 connection. This simple communication protocol is not enough to
connect these devices directly to the Internet. So, we need a sort of gateway
between these devices and the Internet. There can be many possible solutions
to this problem, but these can be boiled down to the following three categories.
- Devices integrated with web server
One possible way of connecting devices to the Internet is to fit an entire
web server into the device. But, most of the embedded
processors do not have enough computing power and memory for the web server.
So, this approach requires more powerful processors and it raises the cost
of the devices.
And, the simple communication protocol used by the devices doesn't have
much bandwidth and it's hard to transfer the required information(HTTP
responses) fast enough.
- PC as a gateway
Most of the devices connected to the Internet are using PC or workstation
as a gateway to the Internet. The devices send minimum
required information such as the status of the sensor to the PC through
it's communication ports(usually RS-232) and the web server running on the
PC collects the information from the device and makes HTML pages and sends
the HTML page back to the web client requesting the page.
In this approach, the device doesn't need extra computing power or memory
for web server. But, the PC is too big and expensive to be used for this
purpose. Suppose that we want to connect the sensor in a corridor to the
Internet. To connect the sensor, we have to deploy a PC around the sensor
in the corridor and it doesn't make sense to put a big and expensive PC
in a corridor only for connecting the sensor to the Internet.
- Small network computer
Instead of using a big and expensive PC for a web server for devices,
why don't we make a small, inexpensive web server and use it for connecting
devices to the Internet?
If we have such a small network computer, then it's really easy to connect
devices located in almost everywhere with low price.
Small network computer solution
The small network computer that will be used for connecting devices to
the Internet must meet the following requirements.
- Ethernet
To be used as a web server, it must have a network capability.
The most popular link layer protocol used in the Internet is
Ethernet. So, it must have an Ethernet port.
- Serial & Parallel port
It must have a serial and parallel port because most of the devices usually
support RS-232 protocol, and sometimes we might have to send signals
directly to the device using parallel port.
- Small Size
The size of it must be small enough to be deployed easily in everywhere.
- Low Cost
It must be cheap rather than expensive and having a larger and powerful
processor.
The Hydra is a small network computer meeting all of the above requirements.
And, the operating system of the Hydra is Linux, so it's really easy to
develope a new application or port an existing application.
How the Hydra can be used?
- Connecting devices to the Internet
The Hydra can be used for connecting devices to the Internet.
Here are some examples of this case.
- Home Automation
Many home appliances can be connected to the Internet and controlled via
web browser.
- Web Camera
Cameras can be connected to the Internet through the Hydra, and
the Internet users can change the direction of the camera.
- Internet portal for handheld devices
The Hydra can also be used as an Internet portal for the handheld devices
such as PalmPilot, Nino, etc.
- Using IrDA
The network connection through the wireless modem is still expensive.
So, it's a good idea to use builtin infrared port of handheld devices
for accessing the Internet.
The Hydra can be used as a gateway between IrDA and IP by plugging IrDA
dongle into the serial port of the Hydra and installing appropriate
software on it. IrDA porting is in progress now.
PCs can also be used for this purpose, but PCs are too big and cannot be
deployed easily. For example, it's not easy to put PCs in the corridor
or the gymnasium. The Hydra can be easily deployed in such places.
- Using RF
In the infrared communication, the two devices must be in the line of
sight, and it doesn't work if the two devices are too far away.
RF doesn't have such limitations.
So, RF can be used like an infrared without such limitations.
Hydra
Home Page
Portolano Project
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jhkang@cs.washington.edu