1 Introduction

The TRF7970A supports three modes: reader/writer, card emulation, and peer-to-peer. This document describes how to use the TRF7970A in peer-to-peer (P2P) active or passive. P2P requires two NFC-enabled devices to communicate using technologies NFC-A or NFC-F at baud rates of 106 kbps (NFC-A), 212 kbps (NFC-F), or 424 kbps (NFC-F). The transceiver that is initially polling and initiates the communication is the initiator. The transceiver that is initially listening is the target.

The initiator always generates the RF field for both active and passive communication modes. However, the target generates its own RF field only for active mode (while the initiator's RF field is disabled) and load modulates the initiator's RF field in passive mode. After the technology selection for either mode has been completed, the higher layers are the same (as shown in Figure 1). The NDEF Push Protocol (NPP) was commonly used on Gingerbread Android NFC devices as the protocol to push NDEF messages from one NFC device to another; however, the Simple NDEF Exchange Protocol (SNEP) has become the standard on Ice Cream Sandwich Android NFC devices and onward.

Figure 1. Peer-to-Peer Layers Including the PHY (TRF7970A)

A 16-bit and a 32-bit microcontroller are used to interface with the TRF7970A to demonstrate a reference example of the peer-to-peer mode. The firmware supports flexible functions that let the user enable or disable different peer-to-peer modes and technologies. The firmware supports both initiator and target for active and passive communication at baud rates of 106 kbps, 212 kbps, and 424 kbps. Additionally, the firmware can send and receive NDEF messages from NFC-enabled smart phones with SNEP.

Table 1 lists the NFC-enabled devices used to validate the firmware.