NFCStack Blocks Are LEGO-Like Building Cubes with Unique Identification

The utility of NFC (near-field communication) comes from the separation of duties between the tags and the receiver. Because the tag receives power from radio waves emitted by the receiver, the tag itself is very affordable. A single tag consists of an antenna and a tiny chip that stores a unique identification number and a small amount of additional data, depending on the specific model. At bulk order prices, NFC tags cost just a few pennies each. That low cost made the NFCStack building block system practical.

NFCStack blocks are a bit like a combination between LEGO bricks and those alphabetic stacking blocks for infants. NFCStack blocks come in different form factors, including cuboids in different sizes and flat caps. The base block (on which the others stack) is a receiver that connects to a computer via USB. The other blocks contain alphanumeric characters and symbols. As a user adds blocks to the stack, the software running on the connected computer will recognize the blocks and display them in the correct order. Thus, a user can spell out different words and phrases by creating a tower of blocks (this also works with horizontal arrangements).

Those familiar with NFC technology will recognize the challenge that NFCStack had to overcome. NFC range is very limited and receivers usually can’t read tags more than a few centimeters away. They also can’t determine the relative distances of two or more nearby tags. NFCStack sidesteps this issue with an extendable antenna system. Each non-receiver block contains an NFC tag to identify itself and a contact-based antenna extension. So adding a block also moves the NFC receiver’s antenna to the top surface of that block. Each antenna extension adds a multiplexed channel, which lets NFCStack identify a given block’s position in the stack.

An Arduino Pro Mini board controls the NFC receiver module, which allows for the multiplexing that would be difficult to accomplish with a standard USB NFC receiver. Standard blocks have contacts on the top and bottom surfaces with wires running between, for extending the receiver antenna. The blocks can contain a single NFC tag in the base or several. When a block has multiple tags, the receiver can detect its orientation so that it can check which face is visible. That lets a single block contain up to four unique characters, increasing the versatility. NFCStack supports up to 12 layers, which sets the upper limits on the number of characters in a string.

As demonstrated, NFCStack has few applications outside of the novelty. But the underlying technology — the ability to stack NFC tags and determine their order — is very useful and potential applications are abundant.