diff --git a/c8_arduino/CMakeLists.txt b/c8_arduino/CMakeLists.txt
index 78c2f7d..f738247 100644
--- a/c8_arduino/CMakeLists.txt
+++ b/c8_arduino/CMakeLists.txt
@@ -10,7 +10,7 @@ generate_arduino_library(checkm8_arduino_libhostshield)
 set(checkm8_arduino_BOARD uno)
 set(checkm8_arduino_HDRS include/User_Setup.h include/Usb.h)
 set(checkm8_arduino_LIBS checkm8_arduino_libhostshield)
-set(checkm8_arduino_SKETCH src/checkm8_arduino.ino)
+set(checkm8_arduino_SKETCH checkm8_arduino.ino)
 set(checkm8_arduino_PROGRAMMER avrispmkii)
 set(checkm8_arduino_PORT /dev/ttyACM0)
 
diff --git a/c8_arduino/src/checkm8_arduino.ino b/c8_arduino/checkm8_arduino.ino
similarity index 99%
rename from c8_arduino/src/checkm8_arduino.ino
rename to c8_arduino/checkm8_arduino.ino
index 72647ba..33a3851 100644
--- a/c8_arduino/src/checkm8_arduino.ino
+++ b/c8_arduino/checkm8_arduino.ino
@@ -1,5 +1,5 @@
-#include "../include/User_Setup.h"
-#include "../include/Usb.h"
+#include "include/User_Setup.h"
+#include "include/Usb.h"
 #include "checkm8_config.h"
 #include "ard_protocol.h"
 
diff --git a/c8_libpayload/CMakeLists.txt b/c8_libpayload/CMakeLists.txt
index 8e23baa..a0ad897 100644
--- a/c8_libpayload/CMakeLists.txt
+++ b/c8_libpayload/CMakeLists.txt
@@ -20,13 +20,10 @@ endforeach(NAME)
 add_subdirectory(pl)
 
 file(MAKE_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/lib)
-add_custom_target(libpayload_sources        # TODO: somehow only pass names that need to be udpated?
-                    DEPENDS ${PL_TARGETS}
-                    BYPRODUCTS ${PL_SRC_LONG}
-                    COMMENT "running librarizer"
-                    COMMAND python3 ${CMAKE_CURRENT_LIST_DIR}/scripts/librarize.py
-                                    ${CMAKE_CURRENT_BINARY_DIR}/pl/bin
-                                    ${CMAKE_CURRENT_BINARY_DIR}/lib)
+add_custom_command(OUTPUT       ${PL_SRC_LONG}
+                    DEPENDS     ${PL_TARGETS}
+                    COMMAND     python3 ${CMAKE_CURRENT_LIST_DIR}/scripts/librarize.py
+                                        ${CMAKE_CURRENT_BINARY_DIR}/pl/bin
+                                        ${CMAKE_CURRENT_BINARY_DIR}/lib)
 
 add_library(payload ${PL_SRC_LONG})
-add_dependencies(payload libpayload_sources)
\ No newline at end of file
diff --git a/c8_libpayload/pl/CMakeLists.txt b/c8_libpayload/pl/CMakeLists.txt
index 3bc4353..43f6468 100644
--- a/c8_libpayload/pl/CMakeLists.txt
+++ b/c8_libpayload/pl/CMakeLists.txt
@@ -13,11 +13,10 @@ set(CMAKE_C_FLAGS "-nostdlib -O")
 file(MAKE_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/bin)
 foreach(PL ${PL_NAMES_SHORT})
     add_executable(payload_${PL} src/${PL}.c)
-    add_custom_command(TARGET payload_${PL} POST_BUILD
-                        BYPRODUCTS ${CMAKE_CURRENT_BINARY_DIR}/bin/payload_${PL}.bin
-                        COMMENT "objcopying ${PL}"
-                        COMMAND ${CMAKE_OBJCOPY}
-                        ARGS -O binary -j .text -j .payload_text -j .payload_data
-                            ${CMAKE_CURRENT_BINARY_DIR}/payload_${PL}
-                            ${CMAKE_CURRENT_BINARY_DIR}/bin/payload_${PL}.bin)
+    add_custom_command(TARGET       payload_${PL} POST_BUILD
+                        BYPRODUCTS  ${CMAKE_CURRENT_BINARY_DIR}/bin/payload_${PL}.bin
+                        COMMAND     ${CMAKE_OBJCOPY}
+                        ARGS        -O binary -j .text -j .payload_text -j .payload_data
+                                    ${CMAKE_CURRENT_BINARY_DIR}/payload_${PL}
+                                    ${CMAKE_CURRENT_BINARY_DIR}/bin/payload_${PL}.bin)
 endforeach(PL)
\ No newline at end of file
diff --git a/c8_libpayload/scripts/librarize.py b/c8_libpayload/scripts/librarize.py
index 72a80ba..1008d94 100644
--- a/c8_libpayload/scripts/librarize.py
+++ b/c8_libpayload/scripts/librarize.py
@@ -1,9 +1,10 @@
 import sys
-from collections import defaultdict
 import os
 
+from collections import defaultdict
+from operator import eq
+
 if __name__ == '__main__':
-    print('ffffffffffffffffff')
     if len(sys.argv) < 3:
         print('Usage: librarize.py [bin names ...] [lib dir]')
         exit(1)
@@ -38,18 +39,33 @@ if __name__ == '__main__':
 
         for i, b in enumerate(fbytes):
             if i % 16 == 0:
-                source_lines[payload_name].append('\n\t\t')
+                source_lines[payload_name][-1] += '\n'
+                source_lines[payload_name].append('\t\t')
 
             source_lines[payload_name][-1] += '0x%02x, ' % b
+            if i == len(fbytes) - 1:
+                source_lines[payload_name][-1] += '\n'
 
-        source_lines[payload_name].append('\n\t};\n')
+        source_lines[payload_name].append('\t};\n')
 
     header_lines.append('\n')
     header_lines.append('#endif //CHECKM8_TOOL_LIBPAYLOAD_H\n')
 
-    with open(lib_dir + '/libpayload.h', 'w+') as f:
-        f.writelines(header_lines)
-
+    files_updated = False
     for sname, lines in source_lines.items():
-        with open(lib_dir + '/' + sname + '.c', 'w+') as f:
-            f.writelines(lines)
\ No newline at end of file
+        sfname = lib_dir + '/' + sname + '.c'
+
+        if os.path.exists(sfname):
+            with open(sfname, 'r') as f:
+                old_lines = f.readlines()
+
+            if all(map(eq, lines, old_lines)):
+                continue
+
+        with open(sfname, 'w+') as f:
+            files_updated = True
+            f.writelines(lines)
+
+    if files_updated:
+        with open(lib_dir + '/libpayload.h', 'w+') as f:
+            f.writelines(header_lines)
\ No newline at end of file