diff --git a/boards/opencm9-04/dist/robotis-loader.py b/boards/opencm9-04/dist/robotis-loader.py
index 3b13dad0a23a..823166aa38c9 100755
--- a/boards/opencm9-04/dist/robotis-loader.py
+++ b/boards/opencm9-04/dist/robotis-loader.py
@@ -3,7 +3,7 @@
 '''
 MIT License
 
-Copyright (c) 2014 Grégoire Passault
+Copyright (c) 2014 Gregoire Passault
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal
@@ -35,11 +35,24 @@
 #
 # https://github.com/Gregwar/robotis-loader
 
-import serial, sys, os, time
+import serial
+import sys
+import os
+import time
 
 print('~~ Robotis loader ~~')
 print('')
 
+
+# Helper function for bytes conversion
+if sys.version_info[:1][0] == 3:
+    def to_ord(val):
+        return ord(chr(val))
+else:
+    def to_ord(val):
+        return ord(val)
+
+
 # Reading command line
 #if len(sys.argv) != 3:
 #    exit('! Usage: robotis-loader.py <serial-port> <binary>')
@@ -49,21 +62,26 @@
 port = os.environ["PORT"]
 binary = os.environ["HEXFILE"]
 
-# Helper that prints a progress bar
+
 def progressBar(percent, precision=65):
-    threshold=precision*percent/100.0
+    """Prints a progress bar."""
+
+    threshold = precision*percent / 100.0
     sys.stdout.write('[ ')
-    for x in xrange(0, precision):
-        if x < threshold: sys.stdout.write('#')
-        else: sys.stdout.write(' ')
+    for x in range(precision):
+        if x < threshold:
+            sys.stdout.write('#')
+        else:
+            sys.stdout.write(' ')
     sys.stdout.write(' ] ')
     sys.stdout.flush()
 
+
 # Opening the firmware file
 try:
     stat = os.stat(binary)
     size = stat.st_size
-    firmware = file(binary, 'rb')
+    firmware = open(binary, 'rb')
     print('* Opening %s, size=%d' % (binary, size))
 except:
     exit('! Unable to open file %s' % binary)
@@ -79,19 +97,19 @@ def progressBar(percent, precision=65):
 s.setDTR(False)
 time.sleep(0.1)
 s.setRTS(False)
-s.write('CM9X')
+s.write(b'CM9X')
 s.close()
 time.sleep(1.0);
 
 print('* Connecting...')
 s = serial.Serial(port, baudrate=115200)
-s.write('AT&LD')
+s.write(b'AT&LD')
 print('* Download signal transmitted, waiting...')
 
 # Entering bootloader sequence
 while True:
     line = s.readline().strip()
-    if line.endswith('Ready..'):
+    if line.endswith(b'Ready..'):
         print('* Board ready, sending data')
         cs = 0
         pos = 0
@@ -100,23 +118,26 @@ def progressBar(percent, precision=65):
             if len(c):
                 pos += len(c)
                 sys.stdout.write("\r")
-                progressBar(100*float(pos)/float(size))
+                progressBar(100 * float(pos) / float(size))
                 s.write(c)
-                for k in range(0,len(c)):
-                    cs = (cs+ord(c[k]))%256
+                for k in range(0, len(c)):
+                    cs = (cs + to_ord(c[k])) % 256
             else:
+                firmware.close()
                 break
         print('')
         s.setDTR(True)
         print('* Checksum: %d' % (cs))
-        s.write(chr(cs))
+        import struct
+        s.write(struct.pack('B', cs))
+        # s.write('{0}'.format(chr(cs)).encode('ascii'))
         print('* Firmware was sent')
     else:
-        if line == 'Success..':
+        if line == b'Success..':
             print('* Success, running the code')
             print('')
-            s.write('AT&RST')
+            s.write(b'AT&RST')
             s.close()
             exit()
         else:
-            print('Board -> '+line)
+            print('Board -> {}'.format(line))