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In the "Internet of Things" there is a push to incorporate net capability on appliances and household object to make then more user friendly. If trying to make a device which can be controlled through a web interface, how powerful of a processing system would be needed for a basic host?

I imagine it wouldn't be very large, since it would only be connecting to one user at a time, but would a standard microprocessor be sufficient for this? Or is a larger dedicated processor required?

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  • \$\begingroup\$ There is no such a thing "standard microprocessor". But most of micros implementing Ethernet stack probably will suffice. \$\endgroup\$
    – Eugene Sh.
    Sep 3, 2015 at 14:59
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    \$\begingroup\$ Google ESP8266 for one example. \$\endgroup\$ Sep 3, 2015 at 15:16
  • \$\begingroup\$ CC3200 is a Wi-Fi certified single-chip microcontroller unit (MCU) with built-in Wi-Fi connectivity. CC3200 SimpleLink Wi-Fi—Consists of Applications Microcontroller (Cortex M4 core), Wi-Fi Network Processor, and Power-Management Subsystems. It is about 17$, check it if you like. \$\endgroup\$ Sep 3, 2015 at 20:35

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If you want to put together your own system with Internet capability, then one option would be to use the TCP/IP stack from Microchip. It includes UDP, TCP, DHCP, SNMP, HTTP, FTP and SSL among others.

The firmware runs on their PIC18, PIC24, and PIC32 processors, which cost as little as $3 or so in quantity (you need at least 64K of Flash). If you are going to run with Wi-Fi, using a dongle then you would want to get their USB libraries also. (Wi-Fi dongles are much cheaper than modules.)

You might be able to put together a board for $17 in quantities of 100 or more (quite a bit more for smaller quantities during development).

PIC32 Processor           3
USB Wi-Fi dongle          2
Connectors (USB, power)   1
Power supply              3
Misc. parts               1
PCB                       1
Assembly                  6
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Total                  $ 17

Figure several weeks (maybe a lot more) of design, board layout, and software development.

If you want to buy rather than build, by far the cheapest solution I can come up with is the Raspberry Pi A+. While everyone seems to be aware of the B+ model at $35, the cost reduced A+, introduced in November of last year, is only $20. It is designed specifically to be used in embedded applications.

Two drawbacks: it doesn't have integrated Wi-Fi, and it has only one USB port. The Wi-Fi can be taken care of with a simple USB dongle costing a couple of bucks. During development, you hook up a hub to the single USB port, and attach a USB keyboard, USB mouse, and USB Wi-Fi dongle to the hub. When it is ready for its embedded application, you remove the hub and insert the Wi-Fi dongle into the single USB port.

It's a little big for some embedded applications at 2.5" x 2.2". But a lot of capability for $20 plus $2 for the dongle, just a little more than rolling your own. And you don't have to build anything from scratch. I got a web server running on a Beaglebone Black (more expensive, but same idea) in a matter of minutes.

If you need something smaller than the Raspberry Pi, you might consider the tiny Arietta G25, which is only 1" by 2", specifically designed for "Internet of Things". It costs 25€, which is currently about $27.75.

It has three USB host ports, but they are only available on headers, not real USB connectors since there isn't room. Like the Raspberry Pi, there is no integrated Wi-Fi. The sell their own module for $7.75

So a little more expensive ($35) but less than half the size.

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Well I built a web-server on a msp430 with an ethernet chip... I assume I could easily port that to their wifi solution as well. I controlled that from an iphone directly by sending GET requests to get DAC readings, switch relays etc. I'd wager I could do something for around $10 for the networking and control portion. Your total system cost might be a little higher if you're adding relays, or other functions.

There's also the new $9 computer from that kickstarter project don't know if they'll be able to deliver or not. It seems to be based on a fairly cheap processor designed for generic Android tablets.

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  • \$\begingroup\$ I agree C.H.I.P. will be the way to go for embedded solutions if the can meet production goals and actually ship units out the door at $9 long term. I bought one during the funding phase, and I think mine's supposed be shipped in January or thereabouts. I'm really impressed by their communications; so far I have gotten 19 email updates on the project. \$\endgroup\$
    – tcrosley
    Sep 3, 2015 at 15:55
  • \$\begingroup\$ Yeah I hope they do make it, sometimes I smile when I see these Kickstarter projects from folks with no manufacturing experience and big pricing promises :) \$\endgroup\$ Sep 3, 2015 at 16:01
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LWiP is a common stack for this, It can be run without a kernel or even a scheduler using interrupt based call backs. So anything that can run LWiP can run a web server, albeit very slowly. It is very easy to meet timing requirements on TCP so even the lamest lowest speed PIC should be able to do it if you are willing to write the software.

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