diff --git a/src/xmlgen.py b/src/xmlgen.py
index 4706ffb..8c1e0ef 100755
--- a/src/xmlgen.py
+++ b/src/xmlgen.py
@@ -12,11 +12,16 @@
 import argparse
 import os
 import pprint
-from typing import IO, Any, Tuple
+from typing import IO, Any, Tuple, List
 import yaml
 
 import utils # local import
 
+# CONSTANTS
+ZM_NUM_ENTRIES = 1024
+C_OUTPUT_FILE = "ZynqMon_addresses.c"
+C_OUTPUT_HEADER = "ZynqMon_addresses.h"
+
 def sensor_size(thedict: dict) -> int:
     """calculate the size of the sensor in bytes"""
     sz = 2 # default size
@@ -41,7 +46,7 @@ def type_to_format(thedict: dict) -> str:
         return None
     return fmt
 
-def open_C_file(fname: str) -> IO[Any]:
+def open_C_file(fname: str, header_fname: str) -> IO[Any]:
     """open the C file and write the header"""
     fout = open(fname, 'w', encoding='ascii')
     print(r"// This file is generated by mcu_generate.py", file=fout)
@@ -54,11 +59,10 @@ def open_C_file(fname: str) -> IO[Any]:
     print(r"//", file=fout)
     print("#include \"Tasks.h\"", file=fout)
     # include the header file we will write later
-    header_fname = args.output.replace('.c', '.h')
     print(f"#include \"{header_fname}\"", file=fout)
     return fout
 
-def write_C_header(fout: IO[Any], fname: str) -> None:
+def write_C_header(header_fname: str, ZMON_VALID_ENTRIES: List[int]) -> None:
     """write the header file"""
     with open(header_fname, encoding="ascii", mode='w') as fheader:
         print(r"// This file is generated by mcu_generate.py", file=fheader)
@@ -140,11 +144,14 @@ def main():
         if args.directory:
             print('Output directory:', args.directory)
 
-
+    # load YAML input file into memory
     with open(args.input_file, encoding='ascii') as f:
         y = yaml.load(f, Loader=yaml.FullLoader)
 
-    # This is the parent(root) tag onto which other tags would be
+    # open C output file for writing
+    c_fout = open_C_file(args.directory + '/' + C_OUTPUT_FILE, C_OUTPUT_HEADER)
+
+    # start XML tree. This is the parent(root) tag onto which other tags will be
     # created
     cm = ET.Element('node')
     cm.set('id', 'CM')
@@ -169,6 +176,10 @@ def main():
 
         if args.verbose:
             print("category_size:", category_size)
+
+        # write the C call to generate the filling of the data structures
+        write_C_call(c_fout, c, sensor_count)
+
         while True:
             # if there are devices
             if device:
@@ -194,7 +205,10 @@ def main():
     if args.verbose:
         print("writing to file", out_name)
     tree.write(out_name)
-
+    # write header file
+    write_C_header(args.directory + '/' + C_OUTPUT_HEADER, [sensor_count, sensor_count])
     pprinter.pprint(summary)
+
+
 if __name__ == "__main__":
     main()