diff --git a/global.c b/global.c
index a2304fb..24ba7b7 100644
--- a/global.c
+++ b/global.c
@@ -29,9 +29,38 @@
 #include <libopencm3/stm32/exti.h> // external interrupt defines
 
 #include "global.h" // common methods
+#include "string.h" // memory utilities
 
 volatile bool button_flag = false;
 
+void * memmem(const void *l, size_t l_len, const void *s, size_t s_len)
+{
+	register char *cur, *last;
+	const char *cl = (const char *)l;
+	const char *cs = (const char *)s;
+
+	/* we need something to compare */
+	if (l_len == 0 || s_len == 0)
+		return NULL;
+
+	/* "s" must be smaller or equal to "l" */
+	if (l_len < s_len)
+		return NULL;
+
+	/* special case where s_len == 1 */
+	if (s_len == 1)
+		return memchr(l, (int)*cs, l_len);
+
+	/* the last position where its possible to find "s" in "l" */
+	last = (char *)cl + l_len - s_len;
+
+	for (cur = (char *)cl; cur <= last; cur++)
+		if (cur[0] == cs[0] && memcmp(cur, cs, s_len) == 0)
+			return cur;
+
+	return NULL;
+}
+
 char* b2s(uint64_t binary, uint8_t rjust)
 {
 	static char string[64+1] = {0}; // the string representation to return
diff --git a/global.h b/global.h
index 184504f..61976ac 100644
--- a/global.h
+++ b/global.h
@@ -127,6 +127,17 @@ extern volatile bool button_flag; /**< flag set when board user button has been
 /** default printf output */
 int _write(int file, char *ptr, int len);
 
+
+/** find the first occurrence of the byte string s in byte string l
+ *  @copyright 2005 Pascal Gloor <pascal.gloor@spale.com>
+ *  @param[in] l byte string to find byte substring in
+ *  @param[in] l_len length of l byte string
+ *  @param[in] s byte byte substring to find in byte string
+ *  @param[in] s_len length of s byte string
+ *  @return pointer to the beginning of the substring, or NULL if the substring is not found
+ */
+void * memmem(const void *l, size_t l_len, const void *s, size_t s_len);
+
 /** get binary representation of a number
  *  @param[in] binary number to represent in binary
  *  @param[in] rjust justify representation with leading zeros