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I was performing a little test today where I wanted to find out what is the maximum distance for two Nexus 7 devices to exchange some very small amount of data. I was very surprised to see that I have to literally tap against their backs for them to be able to exchange information (I used NFC Basic app from Google Play Store). If I touched against their screens or sides it didn't work. I am aware that NFC have read range up to 4-10 cm depending on a reader. What I am looking for is a way to exchange data between devices when I put them side to side. Is it possible to programmatically change the NFC's read range on Android device? I was playing with external USB NFC readers for computers and for as much as I recall there was a way to lower the sensitivity of a reader.

What do I need it for?

Experimental set-up

As you can see on the picture we have 3 Nexus7 devices lying side by side. I need the device A to detect device B but not be able to detect device C. Later, device B should be able to detect device C and device A, C should be able to detect device B but not A and so forth for n amount of devices.

At first, NFC seemed perfect for it but if I cannot extend the range then it is definitely not a way to go. Alternatively I was also thinking about bluetooth. Is it possible to modify the range of bluetooth so that the above mentioned scenario is possible? Maybe you have some other suggestions?

Booyaches
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    In the case of both NFC and Bluetooth, it is a hardware limitation. I have never seen an NFC or Bluetooth device that supports programmatically adjusting the range. If you find one, I would be very interested in checking it out. – Bryan Herbst Aug 13 '13 at 16:20
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    It's all down to the location and orientation of the NFC aerial. Most commonly the are located roughly parallel to the centre-back of the device (in the case of phones, but may be off-centre in larger devices) and to operate need to be oriented in parallel to the aerial in the other device. So, even if you could extend the range you would still need to hold the 2 devices back to back. Though, saying that, I have tried with a second device or an NFC tag held at 90 degrees to the first, and so long as they are within the required proximity, detection is possible. – paulkayuk Aug 14 '13 at 08:06
  • with bluetooth you can check the rssi value (signal strength) http://stackoverflow.com/questions/2149295/android-2-1-how-do-i-poll-the-rssi-value-of-an-existing-bluetooth-connection – Luca Burlizzi Jul 10 '15 at 12:11

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