fmt: add fmt_u16_hex()

sys/fmt/fmt.c

@@ -153,6 +153,11 @@ size_t fmt_hex_bytes(uint8_t *out, const char *hex)
     return final_len;
 }
 
+size_t fmt_u16_hex(char *out, uint16_t val)
+{
+    return fmt_bytes_hex_reverse(out, (uint8_t*) &val, 2);
+}
+
 size_t fmt_u32_hex(char *out, uint32_t val)
 {
     return fmt_bytes_hex_reverse(out, (uint8_t*) &val, 4);

sys/include/fmt.h

@@ -119,6 +119,20 @@ uint8_t fmt_hex_byte(const char *hex);
  */
 size_t fmt_hex_bytes(uint8_t *out, const char *hex);
 
+/**
+ * @brief   Convert a uint16 value to hex string.
+ *
+ * Will write 4 bytes to @p out.
+ * If @p out is NULL, will only return the number of bytes that would have
+ * been written.
+ *
+ * @param[out]  out  Pointer to output buffer, or NULL
+ * @param[in]   val  Value to convert
+ *
+ * @return      4
+ */
+size_t fmt_u16_hex(char *out, uint16_t val);
+
 /**
  * @brief Convert a uint32 value to hex string.
  *