From 36ab835973e32fe2f38688f5df7a5bed9f8b3cb7 Mon Sep 17 00:00:00 2001 From: fros4943 Date: Wed, 3 Feb 2010 14:07:45 +0000 Subject: [PATCH] + calculates CRC for incoming packets (from cooja to cc2420). not yet checking outgoing packets for correct CRC --- .../CC2420RadioPacketConverter.java | 76 ++++++++++++++----- 1 file changed, 55 insertions(+), 21 deletions(-) diff --git a/tools/cooja/apps/mspsim/src/se/sics/cooja/mspmote/interfaces/CC2420RadioPacketConverter.java b/tools/cooja/apps/mspsim/src/se/sics/cooja/mspmote/interfaces/CC2420RadioPacketConverter.java index 98d6e2e8a..7d954db4f 100644 --- a/tools/cooja/apps/mspsim/src/se/sics/cooja/mspmote/interfaces/CC2420RadioPacketConverter.java +++ b/tools/cooja/apps/mspsim/src/se/sics/cooja/mspmote/interfaces/CC2420RadioPacketConverter.java @@ -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; + } + } + }