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Our company is interested in composing an electronic device with the following requirements.

  1. Can connect to the internet through wifi so we can interact with it through a web service.
  2. Battery powered with maximum lifetime (recharged once a month ?).
  3. Flashes a light when syncing with the webservice.
  4. The device should be programmable so to change the led flashing policy.

From what I read on the internet there are no options for efficient wifi enabled boards :( Is that the case?

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    \$\begingroup\$ WiFi takes some minimum power. That will be a very big battery if it needs to supply 1 month of power to a WiFi transciever and processor, even very efficient ones. \$\endgroup\$ – Olin Lathrop Feb 4 '13 at 15:20
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    \$\begingroup\$ @CamilStaps: You can't power it from a button cell period. Those batteries have a peak current of around 300uA, nowhere near the 100-200mA WiFi needs. Lithium Ion is only option here for rechargeable. \$\endgroup\$ – Gustavo Litovsky Feb 4 '13 at 15:53
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    \$\begingroup\$ @GustavoLitovsky nitpick, but it varies by the cell. A run of the mill CR2032 has 5 to 30 mA peak current, not 0.3mA (300 uA). \$\endgroup\$ – Passerby Feb 4 '13 at 16:22
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    \$\begingroup\$ CR123a is not a "button cell", it's a 34x17 mm cylinder for use in camera flashes. Note that the original questioner does not specify a size; you can run WiFi for quite a long time from a 100AH lead-acid battery as used in boats. \$\endgroup\$ – pjc50 Feb 4 '13 at 16:23
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    \$\begingroup\$ @GustavoLitovsky Ti white paper on cr2032 current draw ti.com/lit/wp/swra349/swra349.pdf NordicSemi white paper eetimes.com/ContentEETimes/Documents/Schweber/C0924/… Duracell cr2032 datasheet showing 6ma, 23ma and 30ma draws data.energizer.com/PDFs/cr2032.pdf And then there is the plain practical implementations, led keychain flashlights and throwies. A led with a coin, no resistor, relies on the internal resistance of the cell and the low voltage, will draw roughly 15~20 mA based on a 20 ohm ir, and drain in a few hours. It just works. \$\endgroup\$ – Passerby Feb 4 '13 at 17:57
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What you need really depends on the use cases. How often do you interact with it? The more assumptions you can make, the more often you can go to sleep. What is key for you is lowering the duty cycle and a few other things.

When the WiFi module is asleep, it is not always available for communications (some have a low power polling mode). Going to sleep introduces a delay which in some applications is acceptable and in others (especially human interaction) isn't.

In reality you will need to give a lot more details for you to find a solution, since aside from the hardware, it's really the software you'll need:

1) Support for802.11 g or n need

2) Throughput

3) Are you using embedded linux or a simple microcontroller?

4) Do you need WiFi direct or any specific feature of WiFi?

5) How do you do provisioning, which is connecting the device to the AP and accessing it. Sometimes you can type a key (like a smartphone) but in many others you can't. Some devices have better ways of doing this than others.

And many other questions.

Number 3 and number 4 are easy requirements to meet. It's all in the HTTP webserver.

From my experience, you have two widely available solutions, both from TI:

WL1271 which is targeted towards systems with Linux and WinCE. It has a polling mode that lowers the average current to a few mA.

CC3000: This one is targeted towards the Microcontroller market. Putting it to sleep causes it to draw a few microamps of current, but no communications happen there.

Qualcomm and Broadcom also have some WiFi modules but they're harder to get unless you contact them directly.

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