Over the ACR122U NFC Reader/Writer Device Part I

In the lowest level, NFC communication is performed by a bound between a device which emits such electromagnetic waves, over a specific frequency (13.56 MHz), that another device may receive them and identify them as information. Therefore, the NFC communication instance can be seen in two ways:

1. Passive Mode.- When the device does not hold any power supply and its activation relies on the energy given by the field which was emitted by the reader. In that sense, the passive device answers to the reader by modulating the field. As a consequence, the working period of the devices is greater than the active devices

2. Active Mode.- When both devices alternate the activation of their fields. These devices need a power supply. A device deactivates its field when it is waiting for incoming information.

On the other hand, semi-passive devices are also available and their feature is the combination of the power supply with the passive wait for a reader field. Obviously, the power is not enough to generate a field but it is enough to facilitate the signal reception.

Nowadays, many cellphones have a NFC module incorporated such that NFC tags may automate tasks, transfer contacts information and even more. In that sense, three functionality modes, according to the NFC-Forum, can be identified in the scenario:

1. "Tag Reader/Writer".- "When the device interacts with physical world". These tags may be anything that can be read by a NFC device. There are a lot of tag types, since stickers to simple cards.

2. "Peer to Peer".- "Connect devices through physical proximity". As with any other wireless communication technology, NFC allows the devices to share/exchange information. This point of view mainly focus the "contact information" and light files transference.

3. "Card emulation".- "Connect to a common structure". This perspective refers to the use of NFC cards as smart cards which allow users to perform transactions, authenticate themselves and more.

NFC, in conclusion, might enhance user experience over a broad variety of services. Therefore, software programs and hardware interfaces that can interact with NFC reader/writer devices are becoming more and more popular. 

In these articles we will deal with one of the most popular reader/writer devices, the ACR122U of ACS.

Next article: Over the ACR122U NFC Reader/Writer Device Part II

[1]: Radio Frequency Identification

In case you want to know more:

NFC Forum: http://nfc-forum.org/

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