diff --git a/software/e1-tracer/crc4itu.c b/software/e1-tracer/crc4itu.c
new file mode 100644
index 0000000..f13895a
--- /dev/null
+++ b/software/e1-tracer/crc4itu.c
@@ -0,0 +1,56 @@
+/**
+ * \file
+ * Functions and types for CRC checks.
+ *
+ * Generated on Sat May 12 09:39:22 2018
+ * by pycrc v0.9.1, https://pycrc.org
+ * using the configuration:
+ *  - Width         = 4
+ *  - Poly          = 0x3
+ *  - XorIn         = 0x0
+ *  - ReflectIn     = False
+ *  - XorOut        = 0x0
+ *  - ReflectOut    = False
+ *  - Algorithm     = table-driven
+ */
+#include "crc4itu.h"     /* include the header file generated with pycrc */
+#include <stdlib.h>
+#include <stdint.h>
+
+
+
+/**
+ * Static table used for the table_driven implementation.
+ */
+static const crc_t crc_table[256] = {
+    0x00, 0x03, 0x06, 0x05, 0x0c, 0x0f, 0x0a, 0x09, 0x0b, 0x08, 0x0d, 0x0e, 0x07, 0x04, 0x01, 0x02,
+    0x05, 0x06, 0x03, 0x00, 0x09, 0x0a, 0x0f, 0x0c, 0x0e, 0x0d, 0x08, 0x0b, 0x02, 0x01, 0x04, 0x07,
+    0x0a, 0x09, 0x0c, 0x0f, 0x06, 0x05, 0x00, 0x03, 0x01, 0x02, 0x07, 0x04, 0x0d, 0x0e, 0x0b, 0x08,
+    0x0f, 0x0c, 0x09, 0x0a, 0x03, 0x00, 0x05, 0x06, 0x04, 0x07, 0x02, 0x01, 0x08, 0x0b, 0x0e, 0x0d,
+    0x07, 0x04, 0x01, 0x02, 0x0b, 0x08, 0x0d, 0x0e, 0x0c, 0x0f, 0x0a, 0x09, 0x00, 0x03, 0x06, 0x05,
+    0x02, 0x01, 0x04, 0x07, 0x0e, 0x0d, 0x08, 0x0b, 0x09, 0x0a, 0x0f, 0x0c, 0x05, 0x06, 0x03, 0x00,
+    0x0d, 0x0e, 0x0b, 0x08, 0x01, 0x02, 0x07, 0x04, 0x06, 0x05, 0x00, 0x03, 0x0a, 0x09, 0x0c, 0x0f,
+    0x08, 0x0b, 0x0e, 0x0d, 0x04, 0x07, 0x02, 0x01, 0x03, 0x00, 0x05, 0x06, 0x0f, 0x0c, 0x09, 0x0a,
+    0x0e, 0x0d, 0x08, 0x0b, 0x02, 0x01, 0x04, 0x07, 0x05, 0x06, 0x03, 0x00, 0x09, 0x0a, 0x0f, 0x0c,
+    0x0b, 0x08, 0x0d, 0x0e, 0x07, 0x04, 0x01, 0x02, 0x00, 0x03, 0x06, 0x05, 0x0c, 0x0f, 0x0a, 0x09,
+    0x04, 0x07, 0x02, 0x01, 0x08, 0x0b, 0x0e, 0x0d, 0x0f, 0x0c, 0x09, 0x0a, 0x03, 0x00, 0x05, 0x06,
+    0x01, 0x02, 0x07, 0x04, 0x0d, 0x0e, 0x0b, 0x08, 0x0a, 0x09, 0x0c, 0x0f, 0x06, 0x05, 0x00, 0x03,
+    0x09, 0x0a, 0x0f, 0x0c, 0x05, 0x06, 0x03, 0x00, 0x02, 0x01, 0x04, 0x07, 0x0e, 0x0d, 0x08, 0x0b,
+    0x0c, 0x0f, 0x0a, 0x09, 0x00, 0x03, 0x06, 0x05, 0x07, 0x04, 0x01, 0x02, 0x0b, 0x08, 0x0d, 0x0e,
+    0x03, 0x00, 0x05, 0x06, 0x0f, 0x0c, 0x09, 0x0a, 0x08, 0x0b, 0x0e, 0x0d, 0x04, 0x07, 0x02, 0x01,
+    0x06, 0x05, 0x00, 0x03, 0x0a, 0x09, 0x0c, 0x0f, 0x0d, 0x0e, 0x0b, 0x08, 0x01, 0x02, 0x07, 0x04
+};
+
+
+crc_t crc4itu_update(crc_t crc, const void *data, size_t data_len)
+{
+    const unsigned char *d = (const unsigned char *)data;
+    unsigned int tbl_idx;
+
+    while (data_len--) {
+        tbl_idx = (crc << 4) ^ *d;
+        crc = crc_table[tbl_idx] & 0xf;
+        d++;
+    }
+    return crc & 0xf;
+}