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I am looking for a chip which supports both 802.11 along with 802.15.4 over a simple SPI interface. Does anyone know of any such chip?. Also , is there anyway I can use the existing 802.11 chips on my laptop to actually read the data on the 802.15.4 channels? Is this physically possible? I know that it will be hard but is it physically doable or are there hardware limitations?

user2714712
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Yes, there are physical constraints against using 802.11 circuitry for 802.15-4 (ZigBee?) communication. The two specifications use different frequency bands for physical communications.

For 802.11, Wikipedia mentions operating frequencies of 2.4 GHz, 3.6 GHz, 5 GHz and 60 GHz.

For 802.15-4, Wikipedia mentions operating frequencies of 868.0-868.6 MHz, 902-928 MHz and 2400-2483.5 MHz.

The above need not be comprehensive lists, but they are indicative, that the RF bands are entirely distinct. This means antenna length and RF reception support circuitry have to be very different.

In addition, the RF signal encoding used in the two specifications is different: Arguably this might be solvable in firmware, though there do not seem to be any implementations claiming to do so.

This not to say that some manufacturer may not be able to release chipsets which work on both specifications: After all, USB based BlueTooth + WiFi dongles are pretty inexpensive these days, and those two protocols suffer similar differences in the physical layer.

A cursory web search reveals that Gigaspan announced their GS2000 Wi-Fi and ZigBee IP Single Chip in February this year. It purports to be a System on a Chip (SoC) that covers both specifications. However, it isn't clear whether the product is on the shelves now, or is still vaporware. Further searching may reveal other options.

Anindo Ghosh
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  • Assuming the frequency bands are both 2,4Ghz, channel spacing is different but still on the same frequency should it be able to listen in? Also do you know of any good chips which support both 802.15.4 and 802.11? – user2714712 Sep 18 '13 at 12:30
  • That assumption is meaningless as 802.15-4 is simply not specified for the 2.4 GHz band. Also see my updated answer. – Anindo Ghosh Sep 18 '13 at 12:38
  • http://www.freescale.com/webapp/sps/site/taxonomy.jsp?code=802-15-4_TRANSCEIVERS. look at he seconds Zigbee compliant chip – user2714712 Sep 18 '13 at 12:49
  • Also http://en.wikipedia.org/wiki/IEEE_802.15 802.15.4(a) – user2714712 Sep 18 '13 at 13:06
  • @user2714712 802.15-4a is again a different protocol to 802.11, so it would still need a dual protocol device, such as the example I found, and possibly others you find, as well. Repurposing the existing 802.11 device will still not work. – Anindo Ghosh Sep 18 '13 at 13:24
  • Well just out of curiosity, if the frequency and the modulation schemes are the same then where exactly is the problem coming into the picture? I know we cant use them, else there would have already been such implementations, but I am still curious as to where exactly the issue in combining them lies. The protocol can always be handled by sw as long as we get the packet in. – user2714712 Sep 18 '13 at 14:28
  • @user2714712 If the frequency and the modulation schemes were the same, would we still be speaking of 802.11 and 802.15-4? The reason specifications exist is so that a vast array of manufacturers can design compatible devices. – Anindo Ghosh Sep 18 '13 at 16:25