Wifi: Connecting a Laptop to en embedded system

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

"D Yuniskis" a écrit :

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.

Take a look at this stuff...

Maybe they have appnotes or whatever on direct connection.

John

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)

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.

On a sunny day (Tue, 15 Jun 2010 17:12:58 +0200) it happened "PovTruffe" wrote in :

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.

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.

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.

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.

"Jan Panteltje" a écrit :

are available on the PC.

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...

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!]

Possibly this can get you started:

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

are available on the PC.

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?)

"D Yuniskis" a écrit :

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

"Joerg" a écrit :

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

On a sunny day (Tue, 15 Jun 2010 18:14:29 +0200) it happened "PovTruffe" wrote in :

are available on the PC.

You say a PIC board. To do the WiFi thing I think you need a wireless adaptor, and a TCP stack. As somebody already suggested, hack a WAP654G and you have it all, WiFi, but with a MIPS processor, programmable in C.

I am not against PICs, I use those, but you cannot beat this for price (65 Euro). I have some I/O on it too, analog and digital, with - yes - a PIC.

20 m is not really 'short distance', that rules out IR and probably cheap 430 MHz modules. If you want to stay with PIC only then there is a free microchip TCP stack somewhere.

There are also small ARM based modules available sith TCP, complete ones for under a hundred Euro I have seen annouced.

I use a USB to serial adaptor (several actually.

"D Yuniskis" a écrit :

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.

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.

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

These is alway an "ad hoc" network.

Do you mean, there is no router ?

Don't need it....

hamilton

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

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

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