Wifi: Connecting a Laptop to en embedded system

[PovTruffe]

Hi,

Say you want to design an embedded system that any laptop can
connect to without any Wifi network available. Is that possible ?

Just a point to point communications would be required, not really
a full featured wireless network. A laptop would just sent a few
simple commands to the embedded system.

Maybe BlueTooth would be more appropriate for this application but
this would require adding a costly dongle to most laptops.

Or Zigbee ?

 

[D Yuniskis]

Hi,

Say you want to design an embedded system that any laptop can
connect to without any Wifi network available. Is that possible ?

Just a point to point communications would be required, not really
a full featured wireless network. A laptop would just sent a few
simple commands to the embedded system.

Maybe BlueTooth would be more appropriate for this application but
this would require adding a costly dongle to most laptops.

Or Zigbee ?

Um, serial port? (IrDA if you insist on "wireless")

 

[PovTruffe]

Um, serial port? (IrDA if you insist on "wireless")

It has to be wireless for this application. As far as I know not so many
laptops are equiped with IrDa where the vast majority are wifi enabled.

 

[D Yuniskis]

It has to be wireless for this application. As far as I know not so many
laptops are equiped with IrDa where the vast majority are wifi enabled.

Use an IrDA dongle -- via a serial port, parallel port, USB serial,
etc.

If you want to use WiFi, then configure for an ad hoc network
(assuming your embedded system wants to bear the cost of WiFi)

 

[PovTruffe]

Use an IrDA dongle -- via a serial port, parallel port, USB serial,
etc.

It was my first idea to plug some kind of hardware but I thought maybe
there was a better solution without having to add anything...

If you want to use WiFi, then configure for an ad hoc network
(assuming your embedded system wants to bear the cost of WiFi)

There is no such thing as a wifi network (as I already explained...) unless I
create one with the embedded system I need to control. Maybe there is no
need for a so called network for point to point communication. I dont know
anything about the wifi standard and so dont have any preconceived ideas
of what is possible or not.

 

[FatBytestard]

It was my first idea to plug some kind of hardware but I thought maybe
there was a better solution without having to add anything...


There is no such thing as a wifi network (as I already explained...) unless I
create one with the embedded system I need to control. Maybe there is no
need for a so called network for point to point communication. I dont know
anything about the wifi standard and so dont have any preconceived ideas
of what is possible or not.

You have the Wi-Fi device inside the embedded product become a client
to a Wi-Fi router, and your PC also becomes a client to that router, and
then logs onto the embedded device's user interface 'conole' while on
that local net.

 

[FatBytestard]

Hi,

Say you want to design an embedded system that any laptop can
connect to without any Wifi network available. Is that possible ?

Just a point to point communications would be required, not really
a full featured wireless network. A laptop would just sent a few
simple commands to the embedded system.

Maybe BlueTooth would be more appropriate for this application but
this would require adding a costly dongle to most laptops.

Or Zigbee ?

What you can do...

You make it a device on the laptop that takes control of it. So,
either it dumb logs onto any laptop that OKs an 'install' of it, or you
make it a router itself, and any authenticated user gets to log onto it.



What you should do...

Instead of making an embedded device, you should just hack an existing
device, like an old WRT54G router, that runs Linux and has all the
authentication software and such already built into the Linux that runs
on it. All fully open and hackable.

 

[PovTruffe]

Questions you need to answer here first:
1) Does it need 1 way or 2 way communication.
2) What speed
3) What interfaces are available on the embedded system, and what interfaces are available on the PC.
4) Distance
5) Reliability.

The requirements are very low:
1) Just a few bytes (commands) sent to the embedded system once a while.
Thats one way communication but I dont know yet if status data may be
necessary or even usefull (I am just starting to think about the project).
2) Very low speed but reaction time should not be too low.
3) Any interfaces that could be made available on a 16 bit PIC driven board.
4) Very low distance: max 20m (60ft...)
5) This is not a mission critical system

The embedded system would already have a control panel so the wifi
connection could just be used by some customers who would use their own
laptop. Therefore the laptop could be of any type. My idea is that using wifi
could be the easiest solution for this kind of application (or not?).

For example for a one way low bitrate short distance you can hang a
430 MHz module on the serial port, and dream up some protocol.

Yes but how many laptops have a serial port nowadays ?
In addition most customers dont even know what a serial port is...

 

[D Yuniskis]

It was my first idea to plug some kind of hardware but I thought maybe
there was a better solution without having to add anything...


There is no such thing as a wifi network (as I already explained...) unless I

You can use WiFi in "infrastructure" mode or "ad-hoc".

Infrastructure mode has all of your WiFi devices talking
to (and *thru*) an "access point" (which is often part
of a wireless router, bridge, etc.). Think of infrastructure
as a star topology -- all your wireless devices talk to
the access point in much the same way as a *wired* network
has its devices all connecting to a *hub* (switch).

Ad-hoc mode has your WiFi devices talking to each other
*directly*. Think of this as more of a mesh -- each device
talks *directly* to every device that it wants to
communicate with WITHOUT the presence/intervention of
an "access point" to coordinate those things.

I.e., you can have a "wifi network" with just two wifi
devices (and *no* access point) in much the same way
that you can have a *wired* network with just two
devices (and no hub/switch). [though the analogy breaks
down once you go to more than 2 devices since you can't
just wire together N wired devices whereas you *can*
wireLESS together N WiFi devices!]

 

[Joerg]

Hi,

Say you want to design an embedded system that any laptop can
connect to without any Wifi network available. Is that possible ?

Just a point to point communications would be required, not really
a full featured wireless network. A laptop would just sent a few
simple commands to the embedded system.

Maybe BlueTooth would be more appropriate for this application but
this would require adding a costly dongle to most laptops.

Or Zigbee ?

Possibly this can get you started:

http://techpp.com/2010/01/31/how-to-build-wireless-network-without-router/

 

[D Yuniskis]

The requirements are very low:
1) Just a few bytes (commands) sent to the embedded system once a while.
Thats one way communication but I dont know yet if status data may be
necessary or even usefull (I am just starting to think about the project).
2) Very low speed but reaction time should not be too low.
3) Any interfaces that could be made available on a 16 bit PIC driven board.
4) Very low distance: max 20m (60ft...)
5) This is not a mission critical system

The embedded system would already have a control panel so the wifi
connection could just be used by some customers who would use their own
laptop. Therefore the laptop could be of any type. My idea is that using wifi
could be the easiest solution for this kind of application (or not?).


Yes but how many laptops have a serial port nowadays ?
In addition most customers dont even know what a serial port is...

USB serial port.

Any reason why you can't use USB *directly* (i.e., why
does it have to be wireless?)

Does the exchange have to be interactive? (i.e., can you use
some intermediary to carry data/commands back and forth -- like
a thumb drive?)

 

[PovTruffe]

Ad-hoc mode has your WiFi devices talking to each other
*directly*. Think of this as more of a mesh -- each device
talks *directly* to every device that it wants to
communicate with WITHOUT the presence/intervention of
an "access point" to coordinate those things.

I.e., you can have a "wifi network" with just two wifi
devices (and *no* access point) in much the same way
that you can have a *wired* network with just two
devices (and no hub/switch). [though the analogy breaks
down once you go to more than 2 devices since you can't
just wire together N wired devices whereas you *can*
wireLESS together N WiFi devices!]

"ad-hoc" this is what I was missing in order to be able to find
the proper information on the net. Thanks

 

[PovTruffe]

Possibly this can get you started:

http://techpp.com/2010/01/31/how-to-build-wireless-network-without-router/

Thank you. This is what I was looking for. Just the words "ad-hoc" in fact.

 

[PovTruffe]

USB serial port.

Any reason why you can't use USB *directly* (i.e., why
does it have to be wireless?)

A cable might be used but wireless is a feature of the higher end version of
the system (customers willing to pay more for this version).
However if wifi is too complicated or too expensive I might end up chosing
a simple RF USB dongle.

Does the exchange have to be interactive? (i.e., can you use
some intermediary to carry data/commands back and forth -- like
a thumb drive?)

Yes, ideally customers should not feel any reaction time when a command
is sent to the system from a laptop. I have no idea however if wifi is
appropriate in this respect.

 

[hamilton]

(assuming your embedded system wants to bear the cost of WiFi)

I have wondered about this very thing.

If an embedded system has to purchase a wireless connection and a PC
needs to purchase a wireless connection, what is the cheapest way of do
this.

The cost of WiFi on an embedded system is large, but Bluetooth is not
far behind.

Laptops have WiFi but not always Bluetooth.

So would two Bluetooth devices be cheaper that one embedded WiFi ??

There is also the cost of software in the embedded system.

hamilton

 

[hamilton]

It was my first idea to plug some kind of hardware but I thought maybe
there was a better solution without having to add anything...


There is no such thing as a wifi network (as I already explained...) unless I

These is alway an "ad hoc" network.

Do you mean, there is no router ?

Don't need it....

http://en.wikipedia.org/wiki/Wireless_ad_hoc_network

hamilton

 

[D Yuniskis]

I have wondered about this very thing.

If an embedded system has to purchase a wireless connection and a PC
needs to purchase a wireless connection, what is the cheapest way of do
this.

The cost of WiFi on an embedded system is large, but Bluetooth is not
far behind.

Laptops have WiFi but not always Bluetooth.

But, cell phones have BT (though you have to be picky about
which profiles you expect to work!)

So would two Bluetooth devices be cheaper that one embedded WiFi ??

BT is power hungry. Reasonably high bandwidth. Not as long
range as WiFi. BT stack is... let's say "annoying"?

There is also the cost of software in the embedded system.

ZigBee. Low power, long range, variable data rates, reasonably
simple stack, inexpensive (comparatively speaking) etc.

 

[Charlie E.]

The requirements are very low:
1) Just a few bytes (commands) sent to the embedded system once a while.
Thats one way communication but I dont know yet if status data may be
necessary or even usefull (I am just starting to think about the project).
2) Very low speed but reaction time should not be too low.
3) Any interfaces that could be made available on a 16 bit PIC driven board.
4) Very low distance: max 20m (60ft...)
5) This is not a mission critical system

The embedded system would already have a control panel so the wifi
connection could just be used by some customers who would use their own
laptop. Therefore the laptop could be of any type. My idea is that using wifi
could be the easiest solution for this kind of application (or not?).


Yes but how many laptops have a serial port nowadays ?
In addition most customers dont even know what a serial port is...

Ok, you can have literally ANYTHING on the PIC24 series, from WiFi,
MiWi, etc., the real question here is "What is available on the
notebooks?" In most cases, that is going to be WiFi only. They do
have full TCP/IP stacks for the PIC24, so that won't be a problem.
They are even adding WiFi modules to their product line. Your real
questions are the security and interface to the web...

Charlie
Microchip Design Partner

 

[hamilton]

I see USB-to-BlueTooth dongles selling online for under $2 in single
quantities, and under a dollar (free shipping) on eBay.

How about the embedded side ?

Whats a serial Bluetooth module cost these days ??

Is anyone using one ?

hamilton

 

[hamilton]

I see USB-to-BlueTooth dongles selling online for under $2 in single
quantities, and under a dollar (free shipping) on eBay.

These USB dongles on ebay are for phones.

Can these be used for data as well ??

Of the ones listed, none state they can be used as a serial device.

hamilton