diff --git a/li.strolch.utils/src/main/java/li/strolch/utils/Crc.java b/li.strolch.utils/src/main/java/li/strolch/utils/Crc.java
index b79d4b1d1..c7c10f4e5 100644
--- a/li.strolch.utils/src/main/java/li/strolch/utils/Crc.java
+++ b/li.strolch.utils/src/main/java/li/strolch/utils/Crc.java
@@ -5,7 +5,8 @@ import static li.strolch.utils.helper.ByteHelper.toByteArrayBigEndian;
 /**
  * <p>Implements Cyclic Redundancy Checks</p>
  *
- * <p>Fast byte-wise CRC16 calculation, using the code from Christian d'Heureuse, Inventec Informatik AG, Switzerland, www.source-code.biz</p>
+ * <p>Fast byte-wise CRC16 calculation, using the code from Christian d'Heureuse, Inventec Informatik AG, Switzerland,
+ * www.source-code.biz</p>
  */
 public class Crc {
 
@@ -41,6 +42,24 @@ public class Crc {
 		return toByteArrayBigEndian(crcCcittBytes(bytes));
 	}
 
+	/**
+	 * Implements a CRC-CCITT (XModem), using the initial value 0x0000 and the polynomial 0x1021
+	 *
+	 * @param bytes
+	 * 		the bytes to CRC
+	 * @param src
+	 * 		start if array to do CRC
+	 * @param length
+	 * 		end in array to do CRC
+	 *
+	 * @return the 2 byte CRC
+	 *
+	 * @see <a href="https://www.lammertbies.nl/comm/info/crc-calculation.html">crc-calculation</a>
+	 */
+	public static byte[] crcCcitt(byte[] bytes, int src, int length) {
+		return toByteArrayBigEndian(crcCcittBytes(bytes, src, length));
+	}
+
 	/**
 	 * Implements a CRC-CCITT (XModem), using the initial value 0x0000 and the polynomial 0x1021
 	 *
@@ -52,8 +71,27 @@ public class Crc {
 	 * @see <a href="https://www.lammertbies.nl/comm/info/crc-calculation.html">crc-calculation</a>
 	 */
 	public static short crcCcittBytes(byte[] bytes) {
+		return crcCcittBytes(bytes, 0, bytes.length);
+	}
+
+	/**
+	 * Implements a CRC-CCITT (XModem), using the initial value 0x0000 and the polynomial 0x1021
+	 *
+	 * @param bytes
+	 * 		the bytes to CRC
+	 * @param src
+	 * 		start if array to do CRC
+	 * @param length
+	 * 		end in array to do CRC
+	 *
+	 * @return the CRC as short
+	 *
+	 * @see <a href="https://www.lammertbies.nl/comm/info/crc-calculation.html">crc-calculation</a>
+	 */
+	public static short crcCcittBytes(byte[] bytes, int src, int length) {
 		int crc = 0x0000;
-		for (byte aData : bytes) {
+		for (int i = src; i < length; i++) {
+			byte aData = bytes[i];
 			crc = ((crc << 8) & 0xFF00) ^ (crcTable[(crc >> 8) ^ (aData & 0xFF)] & 0xFFFF);
 		}
 		return (short) crc;
diff --git a/li.strolch.utils/src/test/java/li/strolch/utils/Crc16Test.java b/li.strolch.utils/src/test/java/li/strolch/utils/Crc16Test.java
index 60f8e8852..a65b91cd6 100644
--- a/li.strolch.utils/src/test/java/li/strolch/utils/Crc16Test.java
+++ b/li.strolch.utils/src/test/java/li/strolch/utils/Crc16Test.java
@@ -33,4 +33,11 @@ public class Crc16Test {
 		byte[] expected = { 0x77, (byte) 0x83 };
 		assertArrayEquals(expected, Crc.crcCcitt(data));
 	}
+
+	@Test
+	public void shouldCrc16_4() {
+		byte[] data = { 0x20, (byte) 0x80, 0x00, 0x00, 0x03, 0x00, 0x30 };
+		byte[] expected = { 0x77, (byte) 0x83 };
+		assertArrayEquals(expected, Crc.crcCcitt(data, 1, data.length - 1));
+	}
 }