diff --git a/libraries/GY521/GY521.cpp b/libraries/GY521/GY521.cpp
index 7fc9c0c3..af7f859e 100644
--- a/libraries/GY521/GY521.cpp
+++ b/libraries/GY521/GY521.cpp
@@ -1,7 +1,7 @@
 //
 //    FILE: GY521.cpp
 //  AUTHOR: Rob Tillaart
-// VERSION: 0.3.4
+// VERSION: 0.3.6
 // PURPOSE: Arduino library for I2C GY521 accelerometer-gyroscope sensor
 //     URL: https://github.com/RobTillaart/GY521
 //
@@ -23,6 +23,7 @@
 //  0.3.3   2021-07-05  fix #22 improve maths
 //  0.3.4   2021-07-12  fix #24 improve precision
 //  0.3.5   2021-10-20  update build-CI, badges + #28 add wakeup to begin().
+//  0.3.6   2021-12-18  update library.json, license, minor edits
 
 
 #include "GY521.h"
@@ -317,3 +318,4 @@ int16_t GY521::_WireRead2()
 
 
 // -- END OF FILE --
+
diff --git a/libraries/GY521/GY521.h b/libraries/GY521/GY521.h
index 0785b2f8..3827385a 100644
--- a/libraries/GY521/GY521.h
+++ b/libraries/GY521/GY521.h
@@ -2,7 +2,7 @@
 //
 //    FILE: GY521.h
 //  AUTHOR: Rob Tillaart
-// VERSION: 0.3.4
+// VERSION: 0.3.6
 // PURPOSE: Arduino library for I2C GY521 accelerometer-gyroscope sensor
 //     URL: https://github.com/RobTillaart/GY521
 //
@@ -15,7 +15,7 @@
 #include "Wire.h"
 
 
-#define GY521_LIB_VERSION           (F("0.3.5"))
+#define GY521_LIB_VERSION           (F("0.3.6"))
 
 
 #ifndef GY521_THROTTLE_TIME
diff --git a/libraries/GY521/GY521_registers.h b/libraries/GY521/GY521_registers.h
index fe92d0dd..81dc4e17 100644
--- a/libraries/GY521/GY521_registers.h
+++ b/libraries/GY521/GY521_registers.h
@@ -140,4 +140,6 @@
 #define GY521_FIFO_R_W               0x74
 #define GY521_WHO_AM_I               0x75
 
+
 // -- END OF FILE --
+
diff --git a/libraries/GY521/LICENSE b/libraries/GY521/LICENSE
index d29d575f..4231b05c 100644
--- a/libraries/GY521/LICENSE
+++ b/libraries/GY521/LICENSE
@@ -1,6 +1,6 @@
 MIT License
 
-Copyright (c) 2017-2021 Rob Tillaart
+Copyright (c) 2017-2022 Rob Tillaart
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal
diff --git a/libraries/GY521/README.md b/libraries/GY521/README.md
index b23a3dc5..8ecb8f31 100644
--- a/libraries/GY521/README.md
+++ b/libraries/GY521/README.md
@@ -5,14 +5,15 @@
 [![License: MIT](https://img.shields.io/badge/license-MIT-green.svg)](https://github.com/RobTillaart/GY521/blob/master/LICENSE)
 [![GitHub release](https://img.shields.io/github/release/RobTillaart/GY521.svg?maxAge=3600)](https://github.com/RobTillaart/GY521/releases)
 
+
 # GY521
 
-Arduino library for I2C GY521 accelerometer-gyroscope sensor a.k.a. MCU-6050
+Arduino library for I2C GY521 accelerometer-gyroscope sensor a.k.a. MCU-6050.
 
 
 ## Description
 
-Experimental library for GY521 a.k.a. MCU-6050
+Experimental library for GY521 a.k.a. MCU-6050.
 
 Library is work in progress, in fact it is extracted and extended from an old project.
 It needs to be tested a lot more.
@@ -68,7 +69,7 @@ AD0 connected to VCC => 0x69
 - **bool begin()** Returns true if address can be found on I2C bus.
 - **bool isConnected()** returns true if device can be found on I2C bus.
 - **void reset()** set all internal values to 0 and throttle time to 10 ms.
-- **bool wakeUp()**
+- **bool wakeUp()** idem.
 
 
 ### Throttle
@@ -122,6 +123,16 @@ Read the register PDF for the specific value and meaning of registers.
 - **uint8_t getRegister(uint8_t reg)**
 
 
+## documents
+
+- check details - MPU-6000-Register-Map1.pdf
+
+
+## Operation
+
+See examples, use with care 
+
+
 ## Future
 
 **Should**
@@ -135,13 +146,3 @@ Read the register PDF for the specific value and meaning of registers.
 - calibrate sketch could print code snippet to include...
 - option to read only Accel?
 - option to read only Gyro?
-
-## documents
-
-- check details - MPU-6000-Register-Map1.pdf
-
-
-## Operation
-
-See examples, use with care 
-
diff --git a/libraries/GY521/examples/GY521_performance/GY521_performance.ino b/libraries/GY521/examples/GY521_performance/GY521_performance.ino
index f3388c1c..0463701c 100644
--- a/libraries/GY521/examples/GY521_performance/GY521_performance.ino
+++ b/libraries/GY521/examples/GY521_performance/GY521_performance.ino
@@ -1,7 +1,6 @@
 //
 //    FILE: GY521_performance.ino
 //  AUTHOR: Rob Tillaart
-// VERSION: 0.1.0
 // PURPOSE: minimal demo
 //    DATE: 2021-06-13
 
@@ -44,4 +43,6 @@ void loop()
   delay(1000);
 }
 
-// -- END OF FILE --
\ No newline at end of file
+
+// -- END OF FILE --
+
diff --git a/libraries/GY521/examples/GY521_pitch_roll_yaw/GY521_pitch_roll_yaw.ino b/libraries/GY521/examples/GY521_pitch_roll_yaw/GY521_pitch_roll_yaw.ino
index a99e714e..e27f40eb 100644
--- a/libraries/GY521/examples/GY521_pitch_roll_yaw/GY521_pitch_roll_yaw.ino
+++ b/libraries/GY521/examples/GY521_pitch_roll_yaw/GY521_pitch_roll_yaw.ino
@@ -1,8 +1,7 @@
 //
 //    FILE: GY521_pitch_roll_yaw.ino
 //  AUTHOR: Rob Tillaart
-// VERSION: 0.1.0
-// PURPOSE: demo PRY
+// PURPOSE: demo pitch roll yaw
 //    DATE: 2020-08-06
 
 
@@ -32,7 +31,7 @@ void setup()
 
   sensor.setThrottle();
   Serial.println("start...");
-  
+
   // set calibration values from calibration sketch.
   sensor.axe = 0;
   sensor.aye = 0;
diff --git a/libraries/GY521/examples/readCalibration/readCalibration.ino b/libraries/GY521/examples/readCalibration/readCalibration.ino
index 2107c40b..b1c75a97 100644
--- a/libraries/GY521/examples/readCalibration/readCalibration.ino
+++ b/libraries/GY521/examples/readCalibration/readCalibration.ino
@@ -1,7 +1,6 @@
 //
 //    FILE: readCalibration.ino
 //  AUTHOR: Rob Tillaart
-// VERSION: 0.1.0
 // PURPOSE: read the calibration values / errors for a flat sensor.
 //    DATE: 2020-07-14
 
@@ -105,7 +104,7 @@ void loop()
   sensor.gxe += gx * 0.05;
   sensor.gye += gy * 0.05;
   sensor.gze += gz * 0.05;
-  
+
   counter++;
   delay(100);
 }
diff --git a/libraries/GY521/examples/test1/test1.ino b/libraries/GY521/examples/test1/test1.ino
index a42a8dc7..e7fadb90 100644
--- a/libraries/GY521/examples/test1/test1.ino
+++ b/libraries/GY521/examples/test1/test1.ino
@@ -1,8 +1,7 @@
 //
 //    FILE: test1.ino
 //  AUTHOR: Rob Tillaart
-// VERSION: 0.1.0
-// PURPOSE: minimal demo
+// PURPOSE: minimal demo to test working of the sensor.
 //    DATE: 2020-07-01
 
 
@@ -42,6 +41,7 @@ void setup()
   sensor.gze = 0;
 }
 
+
 void loop()
 {
   sensor.read();
diff --git a/libraries/GY521/examples/test_2/test_2.ino b/libraries/GY521/examples/test_2/test_2.ino
index 6d6d81e0..656a7994 100644
--- a/libraries/GY521/examples/test_2/test_2.ino
+++ b/libraries/GY521/examples/test_2/test_2.ino
@@ -1,8 +1,7 @@
 //
 //    FILE: test_2.ino
 //  AUTHOR: Rob Tillaart
-// VERSION: 0.1.0
-// PURPOSE: test set/get
+// PURPOSE: test set/get functions
 //    DATE: 2020-08-06
 
 
diff --git a/libraries/GY521/keywords.txt b/libraries/GY521/keywords.txt
index 2bca44c9..fe2f4b25 100644
--- a/libraries/GY521/keywords.txt
+++ b/libraries/GY521/keywords.txt
@@ -1,8 +1,10 @@
-# Syntax Coloring Map for GY521
+# Syntax Colouring Map for GY521
 
-# Datatypes (KEYWORD1)
+
+# Data types (KEYWORD1)
 GY521	KEYWORD1
 
+
 # Methods and Functions (KEYWORD2)
 begin	KEYWORD2
 isConnected	KEYWORD2
@@ -39,6 +41,7 @@ setRegister	KEYWORD2
 getRegister	KEYWORD2
 getError	KEYWORD2
 
+
 # Constants (LITERAL1)
 GY521_LIB_VERSION	LITERAL1
 GY521_THROTTLE_TIME	LITERAL1
diff --git a/libraries/GY521/library.json b/libraries/GY521/library.json
index dedac82e..b85456de 100644
--- a/libraries/GY521/library.json
+++ b/libraries/GY521/library.json
@@ -15,8 +15,9 @@
     "type": "git",
     "url": "https://github.com/RobTillaart/GY521.git"
   },
-  "version": "0.3.5",
+  "version": "0.3.6",
   "license": "MIT",
   "frameworks": "arduino",
-  "platforms": "*"
+  "platforms": "*",
+  "headers": "GY521.h"
 }
diff --git a/libraries/GY521/library.properties b/libraries/GY521/library.properties
index 8249d8d4..c0e90094 100644
--- a/libraries/GY521/library.properties
+++ b/libraries/GY521/library.properties
@@ -1,5 +1,5 @@
 name=GY521
-version=0.3.5
+version=0.3.6
 author=Rob Tillaart <rob.tillaart@gmail.com>
 maintainer=Rob Tillaart <rob.tillaart@gmail.com>
 sentence=Arduino library for GY521 angle measurement
diff --git a/libraries/GY521/test/unit_test_001.cpp b/libraries/GY521/test/unit_test_001.cpp
index f5861427..e66b1d06 100644
--- a/libraries/GY521/test/unit_test_001.cpp
+++ b/libraries/GY521/test/unit_test_001.cpp
@@ -31,6 +31,7 @@
 
 unittest_setup()
 {
+  fprintf(stderr, "GY521_LIB_VERSION: %s\n", (char *) GY521_LIB_VERSION);
 }
 
 
@@ -42,7 +43,7 @@ unittest_teardown()
 unittest(test_constructor)
 {
   GY521 sensor(0x69);
-  fprintf(stderr, "VERSION: %s\n", (char *) GY521_LIB_VERSION);
+
   sensor.begin();
   assertEqual(GY521_OK, sensor.getError());
 
@@ -97,8 +98,6 @@ unittest(test_get_set_sensitivity)
 
 unittest(test_constants)
 {
-  fprintf(stderr, "VERSION: %s\n", (char *) GY521_LIB_VERSION);
-
   assertEqual(GY521_OK,                   0);
   assertEqual(GY521_THROTTLED,            1);
   assertEqual(GY521_ERROR_READ,           -1);