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+ calculates CRC for incoming packets (from cooja to cc2420). not yet checking outgoing packets for correct CRC

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This commit is contained in:
fros4943 2010-02-03 14:07:45 +00:00
parent 002e508703
commit 36ab835973
1 changed files with 55 additions and 21 deletions
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76
tools/cooja/apps/mspsim/src/se/sics/cooja/mspmote/interfaces/CC2420RadioPacketConverter.java
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@ -26,7 +26,7 @@
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* $Id: CC2420RadioPacketConverter.java,v 1.12 2010/01/15 10:43:02 fros4943 Exp $
* $Id: CC2420RadioPacketConverter.java,v 1.13 2010/02/03 14:07:45 fros4943 Exp $
*/
package se.sics.cooja.mspmote.interfaces;
@ -35,9 +35,10 @@ import org.apache.log4j.Logger;
import se.sics.cooja.ConvertedRadioPacket;
import se.sics.cooja.RadioPacket;
import se.sics.mspsim.util.CCITT_CRC;
/**
* Converts radio packets between X-MAC/CC24240/Sky and COOJA.
* Converts radio packets between nullmac/CC24240/Sky and COOJA.
* Handles radio driver specifics such as length header and CRC footer.
*
* @author Fredrik Osterlind
@ -47,17 +48,18 @@ public class CC2420RadioPacketConverter {
public static final boolean WITH_PREAMBLE = true;
public static final boolean WITH_SYNCH = true;
public static final boolean WITH_XMAC = true;
public static final boolean WITH_CHECKSUM = false;
public static final boolean WITH_XMAC = false; /* XXX No longer supported. Cross-level requires NULLMAC */
public static final boolean WITH_CHECKSUM = false; /* Contiki checksum. Not CC2420's built-in. */
public static final boolean WITH_TIMESTAMP = true;
public static final boolean WITH_FOOTER = true;
public static final boolean WITH_FOOTER = true; /* CC2420's checksum */
public static byte[] fromCoojaToCC2420(RadioPacket packet) {
byte cc2420Data[] = new byte[6+127];
int pos = 0;
byte packetData[] = packet.getPacketData();
byte len; /* total packet minus preamble(4), synch(1) and length(1) */
short accumulatedCRC = 0;
WrapperCC2420CRC cc2420CRC = new WrapperCC2420CRC();
short contikiCRC = 0;
/* 4 bytes preamble */
if (WITH_PREAMBLE) {
@ -87,47 +89,64 @@ public class CC2420RadioPacketConverter {
len += 2;
}
cc2420Data[pos++] = len;
cc2420CRC.setCRC(0);
cc2420CRC.add(len); /* TODO Should length be included in CRC? */
/* (TODO) 4 byte X-MAC */
/* 4 byte X-MAC: not implemented */
if (WITH_XMAC) {
cc2420Data[pos++] = 1; /* TYPE_DATA */
accumulatedCRC = CRCCoder.crc16Add((byte)0, accumulatedCRC);
cc2420CRC.add(1);
contikiCRC = CRCCoder.crc16Add((byte)0, contikiCRC);
cc2420Data[pos++] = 0;
accumulatedCRC = CRCCoder.crc16Add((byte)0, accumulatedCRC);
cc2420CRC.add(0);
contikiCRC = CRCCoder.crc16Add((byte)0, contikiCRC);
cc2420Data[pos++] = 0; /* XXX sender: 0.0 */
accumulatedCRC = CRCCoder.crc16Add((byte)0, accumulatedCRC);
cc2420CRC.add(0);
contikiCRC = CRCCoder.crc16Add((byte)0, contikiCRC);
cc2420Data[pos++] = 0;
accumulatedCRC = CRCCoder.crc16Add((byte)0, accumulatedCRC);
cc2420CRC.add(0);
contikiCRC = CRCCoder.crc16Add((byte)0, contikiCRC);
cc2420Data[pos++] = 0; /* XXX receiver: 0.0 */
accumulatedCRC = CRCCoder.crc16Add((byte)0, accumulatedCRC);
cc2420CRC.add(0);
contikiCRC = CRCCoder.crc16Add((byte)0, contikiCRC);
cc2420Data[pos++] = 0;
accumulatedCRC = CRCCoder.crc16Add((byte)0, accumulatedCRC);
cc2420CRC.add(0);
contikiCRC = CRCCoder.crc16Add((byte)0, contikiCRC);
}
/* Payload */
for (byte b : packetData) {
accumulatedCRC = CRCCoder.crc16Add(b, accumulatedCRC);
contikiCRC = CRCCoder.crc16Add(b, contikiCRC);
cc2420CRC.add(b & 0xFF);
}
System.arraycopy(packetData, 0, cc2420Data, pos, packetData.length);
pos += packetData.length;
/* 2 bytes checksum */
if (WITH_CHECKSUM) {
cc2420Data[pos++] = (byte) (accumulatedCRC & 0xff);
cc2420Data[pos++] = (byte) ((accumulatedCRC >> 8) & 0xff);
cc2420Data[pos++] = (byte) (contikiCRC & 0xff);
cc2420CRC.add(contikiCRC & 0xFF);
cc2420Data[pos++] = (byte) ((contikiCRC >> 8) & 0xff);
cc2420CRC.add((contikiCRC >> 8) & 0xFF);
}
/* (TODO) 3 bytes timestamp */
if (WITH_TIMESTAMP) {
cc2420Data[pos++] = 0;
cc2420CRC.add(0);
cc2420Data[pos++] = 0;
cc2420CRC.add(0);
cc2420Data[pos++] = 0;
cc2420CRC.add(0);
}
/* (TODO) 2 bytes footer */
/* 2 bytes footer: CC2420's CRC */
if (WITH_FOOTER) {
cc2420Data[pos++] = 0; /* RSSI */
cc2420Data[pos++] = (byte) 0x80; /* CRC and CORRELATION */
/* TODO XXX Workaround for (potential) CC2420 bug:
* it excludes the last byte in the CRC */
int crc = cc2420CRC.getPreviousCRC();
cc2420Data[pos++] = (byte) ((crc >> 8) & 0xff);
cc2420Data[pos++] = (byte) (crc & 0xff);
}
byte cc2420DataStripped[] = new byte[pos];
@ -159,7 +178,7 @@ public class CC2420RadioPacketConverter {
originalLen = len;
pos += 1;
/* (IGNORED) 4 byte X-MAC */
/* 4 byte X-MAC: not implemented */
if (WITH_XMAC) {
pos += 6;
len -= 6;
@ -177,6 +196,7 @@ public class CC2420RadioPacketConverter {
/* (IGNORED) 2 bytes footer */
if (WITH_FOOTER) {
/* TODO Implement */
len -= 2;
}
@ -184,7 +204,7 @@ public class CC2420RadioPacketConverter {
logger.info("Payload length: " + len);*/
byte originalData[] = new byte[originalLen];
System.arraycopy(data, 6, originalData, 0, originalLen);
System.arraycopy(data, 6 /* skipping preamble+synch+len */, originalData, 0, originalLen);
if (len < 0) {
/*logger.warn("No cross-level conversion available: negative packet length");*/
return new ConvertedRadioPacket(new byte[0], originalData);
@ -194,4 +214,18 @@ public class CC2420RadioPacketConverter {
return new ConvertedRadioPacket(convertedData, originalData);
}
private static class WrapperCC2420CRC extends CCITT_CRC {
int previous = 0;
public WrapperCC2420CRC() {
super();
}
public int add(int data) {
previous = getCRC();
return super.add(data);
}
public int getPreviousCRC() {
return previous;
}
}
}