Wireless (802.11?) Communication

[bacterozoid]

I'm looking for a wireless solution for a device I'm working on for a client. (This is academic).

So basically, I want to connect to a device from my computer, and transfer small amounts of data to it (max of about 5 megs) every now and then. I've been looking for some solutions but so far am hitting a wall. What I can find is just too expensive. If possible, this part should cost no more than 20-30 USD.

There's a microcontroller (will likely be an ATMEL AVR of some kind) and flash memory available to it. The client is looking for something with 100ft range, which I think is leaving me with 802.11, which is expensive and I haven't found anything out there that will work.

Anyone know of any solutions in the 802.11 protocol or know of another protocol that will work out? I've looked into zigbee but I'm afraid it's just too slow and not enough range. Is bluetooth a possibility? If necessary we can cut the range down.

Thanks!

 

[Cotowar]

Bluetooth can only go a max of like 30 ft.

You might consider ripping apart an old linksys wireless router for your parts. You can get a 200ft 802.11g signal range out of one of those bad boys easy, and they are pretty easy to play around with too. From what I understand, you are building some sort of transfer device though?

If that's the case, why not just get a wireless USB hub? I have one, you plug it into the router, and you attach your USB device to it, and you can access the device wirelessly via the router. Maybe that's not what you're looking for, but it might help point you in the right direction.

You could also look into some sort of cellular transmitter. Think about it, cell phones can send pictures and videos now, meaning they are transmitting large amounts of data well over 100ft. I was thinking about building something like this myself, but have no clue on where even to start.

Hope my ideas have given you some insight though.

 

[bacterozoid]

The problem with ripping apart a router is that this needs to work as part of another product with an 8 or 16 bit microcontroller. A lot of routers have...from my understanding...basically some sort of PCI card inside of it. That and we don't need a router so much we need a client.

I see where you're going with the wireless USB hub. I'll look into that a little more. It will all depend on how easy it is to interface with the hardware and what datasheets are available for them. But yes, that's essentially what we need (if we go the 802.11 way).

Thanks!

 

[blueroomelectronics]

XBee has plenty of range and mesh networking can give you extended range. The Pro version should have plenty of range. Yet it's only 128kb so yes it's slow but the price is right and it interfaces readily with microcontrollers. Does your AVR have the bandwidth to handle the data you wish to transmit?

 

[bacterozoid]

Hmm, well we haven't decided on an AVR yet (and are open to other options like the MSP430 if it turns out to be better), so I don't know what kind of bandwidth they have. I imagine that will factor into our decision.

So something like this could potentially work?
XBee-PRO 802.15.4 (Formerly Series 1) OEM RF Modules [Hide] - Digi International

What about connecting this to a PC? I believe I've seen some USB dongles that do this but I couldn't find too much information on that.

 

[Cotowar]

Have you ever taken apart a linksys? There are multiple chips in there, I would assume one handles the routing, and one handles the wireless signal. I could be wrong though. I'll look around and see if I can find what the components do. You might be able to just jack a chip from the board in the router and use it in your own device. that would save you loads of time in programming it to handle wireless signals and such. You could also do neat little things like handle multiple signals simultaneously ( ie. talking to multiple devices of yours).

Anyways, I'll see what I can find, and I'll let you know.

 

[Blueteeth]

I assume you want this to be a standard? as you have mentioned the 802.xx standards. Of the shelf wi-fi cards are nice and cheap, but can be horrendous to interface with (PCI, compact flash, PCIMA), and if these are to be used for small microcontroller apps, where portability is a concern, they eat power too.

This guy has documented a ncie little project, but the wifi card can be tough to get hold of (read: old).
http://www.harbaum.org/till/spi2cf/

As far as using a standard protocol is concerned, you're looking at either having to hack an existing device, or interface with it. Bluetooth dongles are cheap, and with the higher datarate of blueteeoth v2 might be an option. For that you would need a USB host, which I believe FTDI do rather cheaply, but may require a lot of software.
FTDI Products

There are some OEM bluetooth modules that communicate using SPI/UART available cheaply, designed purely for embedded apps, negating any nasty over-complicated interfaces:
SparkFun Electronics - Bluetooth DIP Module - SparkFun
SparkFun Electronics - Wireless

Bluetooth has the advantage of making the PC software end a bit easier.

For PCI, a CPLD/FPGA would be mandatory, which would just increase the chip count/hassle a lot more. Not to mention finding decent PCI specs without paying through the nose is tricky. But theres a way around this too. Yep you've guessed it, OEM 802.11* modules.

NXP Launches 802.11n Module to Boost Wireless Home Connectivity
Digi-Key Part Search

Relatively new, its tough to find a good distributor, and to find a cheap one. It should satisfy your need for high throughput and connectivity.

If you're jsut after a one-off, then perhaps nordic devices would help? Datarate wise, they are on parr with zigbee, but many support burst mode (which you could abuse for just brute force datatransfer, ignoring any 'network' features) up to 1MB/s datarate. You'll need a micro at each end, and to connect to the PC, probably some form of USB bridge...its all starting to add up.

If you've got the time for a complete custom setup (non commercial) then you could always use some A/V modules, with 6MHz bandwidth and analogue signals you can get some impressive datarates out of them. I've managed 20MB/s using CPLD's, point-to-point with a very basic protocol. But alas I think its somewhat illegal.

Sorry if I'm ranting, but I'm not entirely sure what direction you are planning to go down.

Blueteeth

 

[bacterozoid]

Thanks for that extensive post! I'll look closer at that tomorrow and let you know if I have any questions, but I want to try to give a clearer idea of what I'm looking for (before I get some sleep):

On on end, there's a PC with software written to communicate with the wireless device. It will send small amounts of control data as well as larger media files (max 5MB) for storage on flash memory for later use.

The device itself will have a moderately powerful microcontroller. It's job is to get instructions from the PC as well as data to store so it can access them later.

Think of it as a wireless MP3 player that you send your songs to wirelessly. (It's not, but it gets the idea across I think).

 

[Blueteeth]

Think of it as a wireless MP3 player that you send your songs to wirelessly. (It's not, but it gets the idea across I think).

For a one-off design, cosidering costs, writing software, PCB space, power consumption, I'd either go with zigbee modules or custom 2.4Ghz wireless jobbies, ala sparkfuns nordic transceivers:

SparkFun Electronics - Transceiver nRF24L01 Module with RP-SMA

They do loads, but I would shy away from on-board antenna's, as external SMA antennas tend to have much better gain (plus the PCB antenna versions claim 62 metres range).

As for through-put...its max over the air rate is 2Mbit/s, maximum packet payload length 32. Roughly averages out to 1mb/s (don't quote me)., Its all designed for low average datarate, burst mode to save power. So thats 125kbytes/s max...5MB file in under a minute...not accounting for errors.

I could be waaay off here, but cheapest solution I can see, plus its SPI interface makes adding it to a micro a snap.

Blueteeth.

Ps. Just managed to talk myself into ordering a few of these, god damn pretty electronics

 

[bacterozoid]

Thanks for all of your suggestions Blueteeth. I'm going to take a close look at some of these, especially that nordic transceiver.

It looks like it has enough speed and range. I'm a little bit confused about how I connect one of these guys to a PC though. Is there some sort of USB device out there that will connect to one without hassle and how would you go about sending data through it? I think that's the biggest point of confusion for me in a lot of these wireless options right now.

 

[Blueteeth]

I think that's the biggest point of confusion for me in a lot of these wireless options right now.

Indeed it is. It seems almost all embedded tranceivers are designed either for directly interfacing with a PC (USB style) or simple protocols, like UART's/SPI for microcontrollers, with no middle ground. This means that, assuming you buy tranceivers, whatever the brand/standard, you'll either have a microcontrollers at each, one for your portable app, and one to interface to a PC (via a USB peripheral chip) OR.....make the PC end easy, but have your portable side interface with USB.

There are USB to serial Bridge chips (FT232RL for example) which use a simple driver on the PC side, but of course then you would need a microcontroller between that and the transceiver to convert serial to SPI. As I said before it all starts to add up very quickly beause each side would have host->micro->RF side. Not to mention software writing.

I can't think of any specific commercial devices that have bluetooth capability and on-board memory (allowing you to add to the memory via PC->bluetooth, then hack it so your micro can read it), except maybe mobile phones. But if you're up for it, theres got to be some USB bluetooth dongles where you can bypass the USB part (if the USB slave is a seperate chip). A lot of hassle and hacking but cheaper!

I do'nt want to confuse you any more by suddenly bringing bluetooth OEM modules back into it, but:
SparkFun Electronics - Bluetooth SMD Module - SparkFun

Again, 'bluetooth' standard will make the PC side of things relatively simple. As a USB bluetooth dongle will just 'see' whatever you call your portable BT device! This shoves all the complexity into your portable thing, you'll still need a micro, some software etc.. but at least you can forget about the PC side of things. As for datarate? who knows...what with bluetooth being a network protocol, it spends much of its RF bandwidth handling that protocol, I wouldn't be able to say what the meaningful user datarate would be. YOu could email sparkfun? I'm sure those guys would be happy to rig it up to a memory card and fire files across the air with a stopwatch on hand

Sorry for the long posts, I'm not trying to confuse you, just perhaps flood you with options, as well as use this thread as an excuse to catch up on the latest in wireless stuff, one falls behind so easily.

Blueteeth

 

[bacterozoid]

Hmm, that's frustrating. I like some of these modules but really don't want to take the time and effort to write all the code, etc for a USB controller, too.

Thanks for the suggestions though. I'm a lot better off now and hopefully I can find a solution based on your suggestions.