+ calculates CRC for incoming packets (from cooja to cc2420). not yet checking outgoing packets for correct CRC
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@ -26,7 +26,7 @@
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* $Id: CC2420RadioPacketConverter.java,v 1.12 2010/01/15 10:43:02 fros4943 Exp $
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* $Id: CC2420RadioPacketConverter.java,v 1.13 2010/02/03 14:07:45 fros4943 Exp $
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*/
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package se.sics.cooja.mspmote.interfaces;
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@ -35,9 +35,10 @@ import org.apache.log4j.Logger;
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import se.sics.cooja.ConvertedRadioPacket;
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import se.sics.cooja.RadioPacket;
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import se.sics.mspsim.util.CCITT_CRC;
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/**
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* Converts radio packets between X-MAC/CC24240/Sky and COOJA.
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* Converts radio packets between nullmac/CC24240/Sky and COOJA.
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* Handles radio driver specifics such as length header and CRC footer.
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*
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* @author Fredrik Osterlind
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@ -47,17 +48,18 @@ public class CC2420RadioPacketConverter {
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public static final boolean WITH_PREAMBLE = true;
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public static final boolean WITH_SYNCH = true;
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public static final boolean WITH_XMAC = true;
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public static final boolean WITH_CHECKSUM = false;
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public static final boolean WITH_XMAC = false; /* XXX No longer supported. Cross-level requires NULLMAC */
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public static final boolean WITH_CHECKSUM = false; /* Contiki checksum. Not CC2420's built-in. */
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public static final boolean WITH_TIMESTAMP = true;
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public static final boolean WITH_FOOTER = true;
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public static final boolean WITH_FOOTER = true; /* CC2420's checksum */
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public static byte[] fromCoojaToCC2420(RadioPacket packet) {
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byte cc2420Data[] = new byte[6+127];
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int pos = 0;
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byte packetData[] = packet.getPacketData();
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byte len; /* total packet minus preamble(4), synch(1) and length(1) */
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short accumulatedCRC = 0;
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WrapperCC2420CRC cc2420CRC = new WrapperCC2420CRC();
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short contikiCRC = 0;
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/* 4 bytes preamble */
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if (WITH_PREAMBLE) {
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@ -87,47 +89,64 @@ public class CC2420RadioPacketConverter {
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len += 2;
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}
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cc2420Data[pos++] = len;
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cc2420CRC.setCRC(0);
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cc2420CRC.add(len); /* TODO Should length be included in CRC? */
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/* (TODO) 4 byte X-MAC */
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/* 4 byte X-MAC: not implemented */
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if (WITH_XMAC) {
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cc2420Data[pos++] = 1; /* TYPE_DATA */
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accumulatedCRC = CRCCoder.crc16Add((byte)0, accumulatedCRC);
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cc2420CRC.add(1);
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contikiCRC = CRCCoder.crc16Add((byte)0, contikiCRC);
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cc2420Data[pos++] = 0;
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accumulatedCRC = CRCCoder.crc16Add((byte)0, accumulatedCRC);
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cc2420CRC.add(0);
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contikiCRC = CRCCoder.crc16Add((byte)0, contikiCRC);
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cc2420Data[pos++] = 0; /* XXX sender: 0.0 */
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accumulatedCRC = CRCCoder.crc16Add((byte)0, accumulatedCRC);
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cc2420CRC.add(0);
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contikiCRC = CRCCoder.crc16Add((byte)0, contikiCRC);
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cc2420Data[pos++] = 0;
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accumulatedCRC = CRCCoder.crc16Add((byte)0, accumulatedCRC);
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cc2420CRC.add(0);
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contikiCRC = CRCCoder.crc16Add((byte)0, contikiCRC);
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cc2420Data[pos++] = 0; /* XXX receiver: 0.0 */
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accumulatedCRC = CRCCoder.crc16Add((byte)0, accumulatedCRC);
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cc2420CRC.add(0);
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contikiCRC = CRCCoder.crc16Add((byte)0, contikiCRC);
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cc2420Data[pos++] = 0;
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accumulatedCRC = CRCCoder.crc16Add((byte)0, accumulatedCRC);
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cc2420CRC.add(0);
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contikiCRC = CRCCoder.crc16Add((byte)0, contikiCRC);
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}
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/* Payload */
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for (byte b : packetData) {
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accumulatedCRC = CRCCoder.crc16Add(b, accumulatedCRC);
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contikiCRC = CRCCoder.crc16Add(b, contikiCRC);
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cc2420CRC.add(b & 0xFF);
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}
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System.arraycopy(packetData, 0, cc2420Data, pos, packetData.length);
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pos += packetData.length;
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/* 2 bytes checksum */
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if (WITH_CHECKSUM) {
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cc2420Data[pos++] = (byte) (accumulatedCRC & 0xff);
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cc2420Data[pos++] = (byte) ((accumulatedCRC >> 8) & 0xff);
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cc2420Data[pos++] = (byte) (contikiCRC & 0xff);
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cc2420CRC.add(contikiCRC & 0xFF);
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cc2420Data[pos++] = (byte) ((contikiCRC >> 8) & 0xff);
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cc2420CRC.add((contikiCRC >> 8) & 0xFF);
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}
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/* (TODO) 3 bytes timestamp */
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if (WITH_TIMESTAMP) {
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cc2420Data[pos++] = 0;
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cc2420CRC.add(0);
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cc2420Data[pos++] = 0;
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cc2420CRC.add(0);
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cc2420Data[pos++] = 0;
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cc2420CRC.add(0);
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}
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/* (TODO) 2 bytes footer */
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/* 2 bytes footer: CC2420's CRC */
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if (WITH_FOOTER) {
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cc2420Data[pos++] = 0; /* RSSI */
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cc2420Data[pos++] = (byte) 0x80; /* CRC and CORRELATION */
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/* TODO XXX Workaround for (potential) CC2420 bug:
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* it excludes the last byte in the CRC */
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int crc = cc2420CRC.getPreviousCRC();
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cc2420Data[pos++] = (byte) ((crc >> 8) & 0xff);
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cc2420Data[pos++] = (byte) (crc & 0xff);
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}
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byte cc2420DataStripped[] = new byte[pos];
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@ -159,7 +178,7 @@ public class CC2420RadioPacketConverter {
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originalLen = len;
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pos += 1;
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/* (IGNORED) 4 byte X-MAC */
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/* 4 byte X-MAC: not implemented */
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if (WITH_XMAC) {
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pos += 6;
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len -= 6;
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@ -177,6 +196,7 @@ public class CC2420RadioPacketConverter {
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/* (IGNORED) 2 bytes footer */
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if (WITH_FOOTER) {
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/* TODO Implement */
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len -= 2;
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}
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@ -184,7 +204,7 @@ public class CC2420RadioPacketConverter {
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logger.info("Payload length: " + len);*/
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byte originalData[] = new byte[originalLen];
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System.arraycopy(data, 6, originalData, 0, originalLen);
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System.arraycopy(data, 6 /* skipping preamble+synch+len */, originalData, 0, originalLen);
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if (len < 0) {
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/*logger.warn("No cross-level conversion available: negative packet length");*/
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return new ConvertedRadioPacket(new byte[0], originalData);
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@ -194,4 +214,18 @@ public class CC2420RadioPacketConverter {
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return new ConvertedRadioPacket(convertedData, originalData);
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}
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private static class WrapperCC2420CRC extends CCITT_CRC {
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int previous = 0;
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public WrapperCC2420CRC() {
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super();
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}
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public int add(int data) {
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previous = getCRC();
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return super.add(data);
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}
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public int getPreviousCRC() {
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return previous;
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}
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}
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}
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