Suggested Starting Point

Hello,

I've been googling for a couple days now and am now looking for suggestions.

What I *think* I want is a single-board computer that:

*Can fit in a 4"x4"x1" space (can be bigger, but not much) *Has 1-3 USB ports that can handle a web cam, wireless ethernet, and a USB drive (thumb or SDcard) from which it can boot. *Preferrably is compatible with the x86 architecture *Would like to have a parallel printer port *Has sufficient Memory - (Not really sure at this point : enough to run apache/php in addition to the OS (Linux)) *Speed-(Not really sure - see "the jist of it") *Is Cheap (less than $100 - preferably less than $50)

I don't need keyboard input, video, or HD/FD controllers

The jist of it: I would like to be able to run a wireless webserver that can serve up web-cam pictures at 30fps.

The parallel port is not for printing but for throwing switches. I supose this could be done through a USB/serial port, but I am not much of a hard-ware guy, so I don't want to mess with programming a PIC to translate a serial command to throw a switch.

It seem I could go several routes. I could go the Linksys route and find a WAP for about $30. But I don't know about adding USB ports to it. Or I could go the "broken" laptop route and shove the guts into my box. But maybe someone from this group could suggest a SBC that will do what I'm looking for.

Thanks! CF

Reply to
deja
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Why have wireless ethernet from USB? Sounds like you will need extra drivers and layers of software to gobble up RAM and overhead slowing your system down and making the main board _possibly_ more expensive. Due to extra USB and RAM requirements, when they may well have ethernet ports already and wireless access points are very cheap anyway.

Considering your requirements and later items I doubt you will get near this price.

Have you done the calculations for how much data just the 30fps at whatever resolution you are choosing will be?

Have you even worked out what picture resolution you need or want?

I doubt it to BOTH of the above questions!

You have to get this data at 30fps from the camera via USB to your very cheap system, then out again over the same USB controller to a USB to wireless.

Work out how much data continuous video is and whether you have the available bandwidth in BITS per second to achieve your requirements bearing in mind the overheads of USB and Wireless AND ethernet.

What is it with people that think USB is cheap therefore it is the answer to EVERYTHING!

Possibly see if you can just simply find an ethernet or wireless webcam that already exist!

Ethernet cameras ALREADY exist!

Wireless cameras (many NOT using wireless ethernet) ALREADY exist!

This data is being sent to some central point (no doubt to connect to internet for a school project), which will have all the grunt power required and more capability to run things like apache/php EASILY.

Considering the nature of most USB controllers, it takes a lot of the system resources to get 30fps VGA (640x480) in on USB 2.0, so I doubt you will have enough system speed or resources left to also send out over USB to wireless ethernet. Especially on a small SBC with limited RAM and USUALLY much SLOWER than desktop PC x86.

You have taken the requirements the WRONG way round and started with x86 and USB then tried to shoehorn what you want to do into it. In reality shoehorn a fast desktop into a cigarette box!

-- Paul Carpenter | snipped-for-privacy@pcserviceselectronics.co.uk PC Services GNU H8 & mailing list info For those web sites you hate

Reply to
Paul Carpenter

$ = k * 1 / sq(")

Just get a 500MHz laptop, but USB bootable laptop don't comes in such slow system.

Probably $200 to $300, usually $500 to $600 for USB bootable.

Approx. 30MB/s raw YUV or 5 to 10 MB/s jpeg. USB can transfer roughly

3 to 4 MB/s. So, you need 2 chanels in and 2 channels out for jpeg. Not all webcam can provide jpeg directly, so your "cheap" sbc would have to do the compressions.

Blame the marketing people, we, the consumers are dumb.

Add a PCI to USB bridge, but you might have to replace the CPU with one having PCI first.

Reply to
linnix

You're right. USB because I knew that many SBC computers have them (even my old 133mhz Pentium MMX laptop has a USB port), and I know that USB 802.11b/g adapters are small and cheap. Most PC104 boards do have ethernet as you indicated - though few (that I've found) are wireless. Obviously if I can get it onboard then I would not also need to go through the USB port. Seems like even if I go the PCMCIA route that it would still require drivers of some sort.

About the best I've found so far is $69 for a new PC104. I could go that high. I'm also contemplating an HP 720LX handheld which are going for about $35 in a "used" condition.

You're right. Maybe 30fps is a bit optimistic. I will have to think about that some more. I think the standard web-cam does 320x240 and

640x480 for "hi rez". Maybe 15fps at the lower res will be palletable (I'll have to experiment).

Because when you don't have a lot of cash to blow you don't have a lot of choices. In my case I'm trying to stick with what I've got laying around the house. It doesn't need to be perfect or pretty. Even if I get this project to simply limp around I will consider a great accomplishment. How's that for setting the bar high.

Yes but I have a USB web cam.

Ah... That's where you're wrong (with all due respect). This project IS the central point. I can see why you think I'm a student (due to your preceived short-comings of me) - but no - I am just a software developer who was fortunate enough to find a really cool robot platform at a garage sale for $2, and who is helping out at "robot camp" in about two months (two of my nephew's are visiting grandma for "robot week"). We have a couple of old radio shack "Arm-a-trons" and small "robot" kits for them to build - as well as the obligatory showing of the animated "Robots" etc. For a 7 and 10 year old (and my 1 month old) it should be quite fun even if this particular project doesn't get very far.

You've made your point. I've decided that I'll take my old laptop and get things "working" as best I can. Maybe I'll just have to re-think the size/mounting aspect I suppse the robot can wear a back-pack with the laptop in it. Won't be as polished but given the time/money constraints...

Well - yeah. I have some basic needs and a small space and limited time to learn a bunch of new stuff. By the way, I started by "shoehorning" an old desktop but there just wasn't enough space - and then of course the power requirements.....

Thanks again - you didn't really give me the answer I was looking for, but it did inspire me to keep moving and not wait for the perfect answer.

-CF

Reply to
deja

snipped-for-privacy@chronofish.com writes

Have you looked at OpenWrt? It runs on wireless routers with built in USB, like the various Asus WL-500...

Ian

Reply to
Ian Braithwaite

Consider this ethernet port or wireless adapters appear as network adapters to the OS so the data is sent from/to network card as packets to/from the network software stack (in simplistic terms).

For USB to wireless/ethernet adapters the data is sent from/to the network stack to/from a pseudo network driver, that then encapsulates the data to send to the USB controller driver (under the same OS) to send to the USB device to de-encapsulate the network traffic to send to/from the wireless/ethernet.

The extra hoops and encapsulation steps (let alone doing any compression) puts extra load on the cpu and RAM requirements, which in turn limits your dataflow. Also more layers of software/drivers to go wrong, be incompatible and other such problems.

Even a PCMCIA wireless card is closer to a network card than a USB device.

I would still suggest using a dedciated USB web cam server plus wireless access point and a LARGE battery.

e.g.

Plug your USB 2.0 camera into the server, test with wired ethernet first. (this unit can take TWO webcams).

The server is a small box that costs about 80.00 UK pounds!

If you were willing to replace the camera there are webcams like ones reviewed here that are webcams to 802.11g in one unit around 100 UK pounds already.

Even the Dlink wifi camera DCS-5300W can be got for around 70 UK pounds.

That is your camera and most of your system.

Alternatively look at

This is wireless but to a TV not the web.

Looking at wireless CCTV that gives a receiver and TV output such as

About 50 UK pounds including camera and receiver.

These from simple google searches for 'webcam server' or 'wireless webcam server'.

This information determines your system requirements, and requirements for the parts of the system (camera, wireless end, what processing e.g. compression, etc.).

It is fine to use what you have if it is capable of doing what you need. "If all you have is a hammer, everything looks like a nail".

I would actually say whatever you do you will _probably_ need to write some software and depending on how the 'throw a switch' translates into hardware interfacing could be an issue in creating interface hardware. If nothing else to take some commands from a web form to execute a CGI programme to then access the parallel port. This turn will need hardware to interface to your 'switches' whatever they may be.

No 'solutions' I have seen do both video transmission and control up stream except to control specific pan/tilt/zoom camera protocols. These are usually specific to each camera.

I would look at telemetry devices and see if you can find a telemetry device that works one way on a different frequency to send a serial byte to a telemetry device with parallel o/p. I am sure they exist and relatively cheaply.

It all depends on what the 'throw a switch' means as in how many, what the 'switch' is controlling in terms of load voltage/currents etc..

Which may be part of the problem, I know you have it but it may be easier cheaper (in money and time) and much quicker to use a better tool.

Hmm this may be central point but I assume the wireless is connecting to something. If you don't need this accessible via the internet I would still consider the wireless CCTV to a TV/VCR option. Unless you need to have the video on another PC for other reasons.

The main thing that made it look like a school project is the method and requirements. Too often I see

must have x86 must use a cheap web cam must have wireless

The standard ingredients of a school project.

I would suggest that getting a bought in solution would be quicker, easier and lighter to power (smaller batteries).

The quicker solution may get more interest from the children.

With broad requirements one can only give broad answers.

--
Paul Carpenter          | paul@pcserviceselectronics.co.uk
    PC Services
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Reply to
Paul Carpenter

Please correct me if I am wrong about this. The above router, as well as others, has USB 1.0 (

Reply to
linnix

The WL-500g has a single USB 1.1. The WL-500g Deluxe/Premium have two USB 2.0. All the ports are host ports, they tend to be used for things like external disks and printers. I'd have thought USB 1.1 was fine for a webcam.

I don't know how much CPU the application would require, you may be right that it would be hopelessly underpowered.

:-)

Ian

Reply to
Ian Braithwaite

Which have extremely slow data rates compared with 15 frames per second and upwards of cameras. Even webcams doing continuous video.

I would have thought, by looking at earlier post in the thread, that mentions some figures, it should become clear. USB1/1.1 has a CLOCK rate of approx 12MHz, so you might be lucky and get 2 frames a second (depending on size of image and if camera has compression).

If CPU has to do compression as well, underpowered.

--
Paul Carpenter          | paul@pcserviceselectronics.co.uk
    PC Services
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Reply to
Paul Carpenter

I've seen the Philips 740/840 webcam used with Linux on some mobile robot projects with great success. With USB1 it manages 5fps at 320x240 uncompressed (that comes to 4.6Mb/s data) and 30fps, or 640x480 at 15fps, with the camera's built in compression.

formatting link
has the full table.)

So it might not be quite as hopeless as you seem to think. It depends on the application.

Ian

Reply to
Ian Braithwaite

Which exactly echos my point above stated again below

(depending on size of image and if camera has compression).

In my books 320 x 240 is toy vision (and usually very grainy on most cameras)

640 x 480 (as raw size) is the smallest frame size I even consider.

The original poster was trying to achieve 30fps and preferably 640x480.

Lots of talk of software and cameras, and nothing about minimum hardware requirements, considering original question this is important.

Considering original request and expected SBC size and hence power/resources I think my answer was nearer the mark.

--
Paul Carpenter          | paul@pcserviceselectronics.co.uk
    PC Services
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Reply to
Paul Carpenter

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