Development

.buildkite/pipeline.yml

@@ -4,11 +4,6 @@ steps:
       - export SONAR_TOKEN=$(buildkite-agent secret get SONAR_TOKEN)
       - export NVD_API_KEY=$(buildkite-agent secret get nvd_api_key)
       - mvn -Dgpg.skip=true clean deploy -Psnapshot
-      - mvn sonar:sonar -Dsonar.login=${SONAR_TOKEN}
-    plugins:
-      - test-collector#v1.0.0:
-          files: "target/surefire-reports/*.xml"
-          format: "junit"
     env:
       BUILDKITE_ANALYTICS_TOKEN: "$(buildkite-agent secret get SchemasBuildkiteAnalytics)"
       SONAR_TOKEN: "${SONAR_TOKEN}"

README.md

@@ -73,6 +73,8 @@ Dependencies:
 
 NMEA 2000 is treated as a **specialised J1939 profile**, preserving correct layering and reuse.
 
+Want to dive deeper? 
+[![Ask DeepWiki](https://deepwiki.com/badge.svg)](https://deepwiki.com/Maps-Messaging/canbus_interface)
 ---
 
 ## Current Capabilities

canbus-J1939/src/main/java/io/mapsmessaging/canbus/j1939/CanId.java

@@ -16,60 +16,80 @@
  *  See the License for the specific language governing permissions and
  *  limitations under the License.
  */
-
 package io.mapsmessaging.canbus.j1939;
 
 import lombok.Getter;
+import lombok.RequiredArgsConstructor;
 
 @Getter
+@RequiredArgsConstructor
 public class CanId {
 
+  private static final int EXTENDED_ID_MASK = 0x1FFFFFFF;
+
+  private static final int PRIORITY_SHIFT = 26;
+  private static final int PRIORITY_MASK = 0x7;
+
+  private static final int DATA_PAGE_SHIFT = 24;
+  private static final int DATA_PAGE_MASK = 0x1;
+
+  private static final int PDU_FORMAT_SHIFT = 16;
+  private static final int BYTE_MASK = 0xFF;
+
+  private static final int PDU1_MAX_PF = 239;
+  private static final int BROADCAST_ADDRESS = 255;
+
   private final int priority;
   private final int pgn;
   private final int sourceAddress;
   private final int destinationAddress;
 
-  private CanId(int priority, int pgn, int sourceAddress, int destinationAddress) {
-    this.priority = priority;
-    this.pgn = pgn;
-    this.sourceAddress = sourceAddress;
-    this.destinationAddress = destinationAddress;
-  }
-
-  /**
-   * Parse a 29-bit extended CAN identifier used by NMEA 2000.
-   *
-   * Layout (J1939 style):
-   * - Priority: bits 26..28 (3 bits)
-   * - PGN: derived from PF/PS/DP
-   * - Source: bits 0..7
-   *
-   * PGN rules:
-   * - PF < 240 (PDU1): PGN uses PF and DP, PS is destination and excluded from PGN (low byte becomes 0)
-   * - PF >= 240 (PDU2): PGN includes PF and PS, destination is "global" (255)
-   */
   public static CanId parse(int canIdentifier) {
-    int identifier = canIdentifier & 0x1FFFFFFF;
+    int identifier = canIdentifier & EXTENDED_ID_MASK;
 
-    int priority = (identifier >> 26) & 0x07;
-    int pf = (identifier >> 16) & 0xFF;
-    int ps = (identifier >> 8) & 0xFF;
-    int source = identifier & 0xFF;
-    int dataPage = (identifier >> 24) & 0x01;
+    int priority = (identifier >> PRIORITY_SHIFT) & PRIORITY_MASK;
+    int pduFormat = (identifier >> PDU_FORMAT_SHIFT) & BYTE_MASK;
+    int pduSpecific = (identifier >> 8) & BYTE_MASK;
+    int sourceAddress = identifier & BYTE_MASK;
+    int dataPage = (identifier >> DATA_PAGE_SHIFT) & DATA_PAGE_MASK;
 
     int pgn;
-    int destination;
+    int destinationAddress;
 
-    if (pf < 240) {
-      // PDU1
-      destination = ps;
-      pgn = (dataPage << 16) | (pf << 8);
+    if (pduFormat <= PDU1_MAX_PF) {
+      destinationAddress = pduSpecific;
+      pgn = (dataPage << 16) | (pduFormat << 8);
     } else {
-      // PDU2
-      destination = 255;
-      pgn = (dataPage << 16) | (pf << 8) | ps;
+      destinationAddress = BROADCAST_ADDRESS;
+      pgn = (dataPage << 16) | (pduFormat << 8) | pduSpecific;
+    }
+
+    return new CanId(priority, pgn, sourceAddress, destinationAddress);
+  }
+
+  public boolean isPdu1() {
+    return (pgn & BYTE_MASK) == 0;
+  }
+
+  public boolean isPdu2() {
+    return !isPdu1();
+  }
+
+  public boolean isBroadcast() {
+    return isPdu2();
+  }
+
+  public Integer getDestinationAddressOrNull() {
+    if (isPdu1()) {
+      return destinationAddress;
     }
+    return null;
+  }
 
-    return new CanId(priority, pgn, source, destination);
+  public Integer getGroupExtensionOrNull() {
+    if (isPdu2()) {
+      return pgn & BYTE_MASK;
+    }
+    return null;
   }
-}
+}

canbus-J1939/src/main/java/io/mapsmessaging/canbus/j1939/CanIdBuilder.java

@@ -16,11 +16,15 @@
  *  See the License for the specific language governing permissions and
  *  limitations under the License.
  */
-
 package io.mapsmessaging.canbus.j1939;
 
 public class CanIdBuilder {
 
+  private static final int EXTENDED_ID_MASK = 0x1FFFFFFF;
+  private static final int PRIORITY_MASK = 0x07;
+  private static final int BYTE_MASK = 0xFF;
+  private static final int PDU1_MAX_PF = 239;
+
   private CanIdBuilder() {
   }
 
@@ -35,22 +39,29 @@ private CanIdBuilder() {
    * - SA: bits 0..7
    *
    * PGN rules:
-   * - PF < 240 => PDU1 => PS is destination
+   * - PF < 240 => PDU1 => PS is destination, PGN low byte must be 0x00
    * - PF >= 240 => PDU2 => PS comes from PGN low byte, destination implied global
    */
   public static int build(int pgn, int priority, int sourceAddress, int destinationAddress) {
-    int prio = priority & 0x07;
+    if (priority < 0 || priority > PRIORITY_MASK) {
+      throw new IllegalArgumentException("priority must be in range 0..7, got " + priority);
+    }
+
+    int prio = priority & PRIORITY_MASK;
     int dp = (pgn >> 16) & 0x01;
-    int pf = (pgn >> 8) & 0xFF;
+    int pf = (pgn >> 8) & BYTE_MASK;
 
     int ps;
-    if (pf < 240) {
-      ps = destinationAddress & 0xFF;
+    if (pf <= PDU1_MAX_PF) {
+      if ((pgn & BYTE_MASK) != 0) {
+        throw new IllegalArgumentException("PDU1 PGN must have low byte 0x00, got 0x" + Integer.toHexString(pgn));
+      }
+      ps = destinationAddress & BYTE_MASK;
     } else {
-      ps = pgn & 0xFF;
+      ps = pgn & BYTE_MASK;
     }
 
-    int sa = sourceAddress & 0xFF;
+    int sa = sourceAddress & BYTE_MASK;
 
     int identifier = 0;
     identifier |= (prio << 26);
@@ -59,6 +70,7 @@ public static int build(int pgn, int priority, int sourceAddress, int destinatio
     identifier |= (ps << 8);
     identifier |= sa;
 
-    return identifier & 0x1FFFFFFF;
+    return identifier & EXTENDED_ID_MASK;
   }
+
 }

canbus-J1939/src/test/java/io/mapsmessaging/canbus/j1939/CanIdBuilderTest.java

@@ -21,8 +21,7 @@
 
 import org.junit.jupiter.api.Test;
 
-import static org.junit.jupiter.api.Assertions.assertEquals;
-import static org.junit.jupiter.api.Assertions.assertTrue;
+import static org.junit.jupiter.api.Assertions.*;
 
 class CanIdBuilderTest {
 
@@ -61,9 +60,21 @@ void build_pdu2_pfGreaterOrEqual240_usesPgnLowByteInPs() {
   }
 
   @Test
-  void build_priorityIsMaskedTo3Bits() {
+  void build_priorityOutsideRangeThrows() {
     int pgn = 0x00EA00; // PF < 240 so destination is used
-    int priority = 0xFF; // should become 7
+    int priority = 0xFF; // invalid
+    int sourceAddress = 0x01;
+    int destinationAddress = 0x02;
+
+    assertThrows(IllegalArgumentException.class,
+        () -> CanIdBuilder.build(pgn, priority, sourceAddress, destinationAddress));
+  }
+
+
+  @Test
+  void build_priorityIsPreservedWhenValid() {
+    int pgn = 0x00EA00;
+    int priority = 7;
     int sourceAddress = 0x01;
     int destinationAddress = 0x02;
 
@@ -72,6 +83,7 @@ void build_priorityIsMaskedTo3Bits() {
     assertEquals(7, extractPriority(id));
   }
 
+
   @Test
   void build_sourceAndDestinationAreMaskedTo8Bits() {
     int pgn = 0x00EA00; // PF < 240 => destination used