NfcA.java revision 74fe6c6b245ebe7d3b3d96962c32980d88dca4f5 
1/*
2 * Copyright (C) 2010 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package android.nfc.tech;
18
19import android.nfc.Tag;
20import android.os.Bundle;
21import android.os.RemoteException;
22
23import java.io.IOException;
24
25/**
26 * Provides access to NFC-A (ISO 14443-3A) properties and I/O operations on a {@link Tag}.
27 *
28 * <p>Acquire a {@link NfcA} object using {@link #get}.
29 * <p>The primary NFC-A I/O operation is {@link #transceive}. Applications must
30 * implement their own protocol stack on top of {@link #transceive}.
31 */
32public final class NfcA extends BasicTagTechnology {
33    /** @hide */
34    public static final String EXTRA_SAK = "sak";
35    /** @hide */
36    public static final String EXTRA_ATQA = "atqa";
37
38    private short mSak;
39    private byte[] mAtqa;
40
41    /**
42     * Get an instance of {@link NfcA} for the given tag.
43     * <p>Returns null if {@link NfcA} was not enumerated in {@link Tag#getTechList}.
44     * This indicates the tag does not support NFC-A.
45     * <p>Does not cause any RF activity and does not block.
46     *
47     * @param tag an NFC-A compatible tag
48     * @return NFC-A object
49     */
50    public static NfcA get(Tag tag) {
51        if (!tag.hasTech(TagTechnology.NFC_A)) return null;
52        try {
53            return new NfcA(tag);
54        } catch (RemoteException e) {
55            return null;
56        }
57    }
58
59    /** @hide */
60    public NfcA(Tag tag) throws RemoteException {
61        super(tag, TagTechnology.NFC_A);
62        Bundle extras = tag.getTechExtras(TagTechnology.NFC_A);
63        mSak = extras.getShort(EXTRA_SAK);
64        mAtqa = extras.getByteArray(EXTRA_ATQA);
65    }
66
67    /**
68     * Return the ATQA/SENS_RES bytes from tag discovery.
69     *
70     * <p>Does not cause any RF activity and does not block.
71     *
72     * @return ATQA/SENS_RES bytes
73     */
74    public byte[] getAtqa() {
75        return mAtqa;
76    }
77
78    /**
79     * Return the SAK/SEL_RES bytes from tag discovery.
80     *
81     * <p>Does not cause any RF activity and does not block.
82     *
83     * @return SAK bytes
84     */
85    public short getSak() {
86        return mSak;
87    }
88
89    /**
90     * Send raw NFC-A commands to the tag and receive the response.
91     *
92     * <p>Applications must not append the EoD (CRC) to the payload,
93     * it will be automatically calculated.
94     * <p>Applications must only send commands that are complete bytes,
95     * for example a SENS_REQ is not possible (these are used to
96     * manage tag polling and initialization).
97     *
98     * <p>This is an I/O operation and will block until complete. It must
99     * not be called from the main application thread. A blocked call will be canceled with
100     * {@link IOException} if {@link #close} is called from another thread.
101     *
102     * @param data bytes to send
103     * @return bytes received in response
104     * @throws TagLostException if the tag leaves the field
105     * @throws IOException if there is an I/O failure, or this operation is canceled
106     */
107    public byte[] transceive(byte[] data) throws IOException {
108        return transceive(data, true);
109    }
110}
111