diff --git a/CHANGELOG.md b/CHANGELOG.md
index 65caf11..6f0a235 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,11 +6,20 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/)
 and this project adheres to [Semantic Versioning](http://semver.org/).
 
 
+## [0.2.0] - 2023-12-04
+- refactor API, more in line with other Wire based libs.
+- update readme.md
+- added **isConnected()**
+- added asynchronous interface.
+- rewrote the synchronous interface.
+- add examples.
+
+----
+
 ## [0.1.3] - 2023-11-22
 - update readme.md
 - fix version number
 
-
 ## [0.1.2] - 2022-11-26
 - Add RP2040 support to build-CI.
 - Add CHANGELOG.md
diff --git a/README.md b/README.md
index b4ee932..a806314 100644
--- a/README.md
+++ b/README.md
@@ -16,13 +16,22 @@ Arduino library specific for AVR tiny processors.
 
 ## Description
 
-**Experimental**
+The tinySHT2x is an **Experimental** Arduino library to read the SHT2X sensor.
+This sensor provides temperature and humidity.
+
+The library is meant for AVR only, tiny platform, so it is minimal (not?) portable.
+
+
+#### 0.2.0 Breaking change
+
+Version 0.2.0 introduced a breaking change.
+Wire parameter has moved from **begin()** to the Constructor.
+The user has to call **Wire.begin()** before calling **begin()**.
 
-Not portable, AVR only
 
 #### Related
 
-Based upon https://github.com/RobTillaart/SHT2x
+- https://github.com/RobTillaart/SHT2x (based upon).
 
 
 ## Interface
@@ -31,6 +40,33 @@ Based upon https://github.com/RobTillaart/SHT2x
 #include "tinySHT2x.h"
 ```
 
+#### Functions
+
+- **tinySHT2x(TwoWire \* wire = &Wire)** Constructor
+- **bool begin()** initializes internals. Returns true if device can be found.
+- **bool isConnected()** Returns true if device can be found.
+- **bool reset()** sends SOFT_RESET command to sensor.
+returns false if I2C failed to send it.
+
+
+#### Async interface
+
+With the Async interface the user must watch keep track of the appropriate
+delay between the request and read. 
+For temperature this is typical around 70 millis and for humidity 30 millis().
+
+- **void requestTemperature()** sends GET_TEMPERATURE command to sensor.
+- **void requestHumidity()** sends GET_HUMIDITY command to sensor.
+- **float readTemperature()** fetches data from the sensor.
+- **float readHumidity()** fetches data from the sensor.
+  
+#### Sync interface
+
+- **float getTemperature(uint8_t del = 70)** requests and read the temperature.
+It uses a delay of 70 milliseconds which can be tuned by the user.
+- **float getHumidity(uint8_t del = 30)**  requests and read the humidity.
+It uses a delay of30 milliseconds which can be tuned by the user.
+  
 - see https://github.com/RobTillaart/SHT2x
 
 
@@ -45,6 +81,9 @@ Based upon https://github.com/RobTillaart/SHT2x
 
 #### Could
 
+- investigate async interface
+  - splitting requestHumidity() and getHumidity().
+  - idem for temperature. 
 - Can a tiny have another Wire than Wire?
 - Check the status bit (temperature / humidity flag) 
   - datasheet page 8, LSB bit 1 - bit 0 not used)
diff --git a/documents/Download Center - Sensirion.url b/documents/Download Center - Sensirion.url
new file mode 100644
index 0000000..4bd37de
--- /dev/null
+++ b/documents/Download Center - Sensirion.url	
@@ -0,0 +1,2 @@
+[InternetShortcut]
+URL=https://www.sensirion.com/en/download-center/humidity-sensors/humidity-temperature-sensor-sht2x-digital-i2c-accurate/
diff --git a/documents/SHT20_datasheet.pdf b/documents/SHT20_datasheet.pdf
new file mode 100644
index 0000000..34678b2
Binary files /dev/null and b/documents/SHT20_datasheet.pdf differ
diff --git a/documents/SHT21_datasheet.pdf b/documents/SHT21_datasheet.pdf
new file mode 100644
index 0000000..6f1f393
Binary files /dev/null and b/documents/SHT21_datasheet.pdf differ
diff --git a/documents/Sensirion_Humidity_SHT21_Sample_Code_V1.2.pdf b/documents/Sensirion_Humidity_SHT21_Sample_Code_V1.2.pdf
new file mode 100644
index 0000000..fbe4ed6
Binary files /dev/null and b/documents/Sensirion_Humidity_SHT21_Sample_Code_V1.2.pdf differ
diff --git a/documents/Sensirion_Humidity_Sensors_SHT25_Datasheet.pdf b/documents/Sensirion_Humidity_Sensors_SHT25_Datasheet.pdf
new file mode 100644
index 0000000..589157d
Binary files /dev/null and b/documents/Sensirion_Humidity_Sensors_SHT25_Datasheet.pdf differ
diff --git a/examples/tinySHT2x_demo/tinySHT2x_demo.ino b/examples/tinySHT2x_demo/tinySHT2x_demo.ino
index f3b0fb2..4371224 100644
--- a/examples/tinySHT2x_demo/tinySHT2x_demo.ino
+++ b/examples/tinySHT2x_demo/tinySHT2x_demo.ino
@@ -16,6 +16,7 @@ void setup()
   Serial.begin(115200);
   Serial.println(__FILE__);
 
+  Wire.begin();
   sht.begin();
 }
 
@@ -29,5 +30,5 @@ void loop()
 }
 
 
-// -- END OF FILE --
+//  -- END OF FILE --
 
diff --git a/examples/tinySHT2x_demo_async/.arduino-ci.yml b/examples/tinySHT2x_demo_async/.arduino-ci.yml
new file mode 100644
index 0000000..8d78299
--- /dev/null
+++ b/examples/tinySHT2x_demo_async/.arduino-ci.yml
@@ -0,0 +1,12 @@
+compile:
+  # Choosing to run compilation tests on 2 different Arduino platforms
+  platforms:
+    - uno
+    # - due
+    # - zero
+    - leonardo
+    # - m4
+    #- esp32
+    # - esp8266
+    - mega2560
+    # - trinket
diff --git a/examples/tinySHT2x_demo_async/tinySHT2x_demo_async.ino b/examples/tinySHT2x_demo_async/tinySHT2x_demo_async.ino
new file mode 100644
index 0000000..25fcc07
--- /dev/null
+++ b/examples/tinySHT2x_demo_async/tinySHT2x_demo_async.ino
@@ -0,0 +1,38 @@
+//
+//    FILE: tinySHT2x_demo_async.ino
+//  AUTHOR: Rob Tillaart
+// PURPOSE: demo
+//     URL: https://github.com/RobTillaart/tinySHT2x
+
+
+#include "Wire.h"
+#include "tinySHT2x.h"
+
+tinySHT2x sht;
+
+
+void setup()
+{
+  Serial.begin(115200);
+  Serial.println(__FILE__);
+
+  Wire.begin();
+  sht.begin();
+}
+
+
+void loop()
+{
+  sht.requestTemperature();
+  delay(65);  //  tune to work
+  Serial.print(sht.readTemperature());
+  Serial.print("\t");
+  
+  sht.requestHumidity();
+  delay(28);  //  tune to work
+  Serial.println(sht.getHumidity());
+  delay(1000);
+}
+
+
+//  -- END OF FILE --
diff --git a/examples/tinySHT2x_demo_delay/.arduino-ci.yml b/examples/tinySHT2x_demo_delay/.arduino-ci.yml
new file mode 100644
index 0000000..8d78299
--- /dev/null
+++ b/examples/tinySHT2x_demo_delay/.arduino-ci.yml
@@ -0,0 +1,12 @@
+compile:
+  # Choosing to run compilation tests on 2 different Arduino platforms
+  platforms:
+    - uno
+    # - due
+    # - zero
+    - leonardo
+    # - m4
+    #- esp32
+    # - esp8266
+    - mega2560
+    # - trinket
diff --git a/examples/tinySHT2x_demo_delay/tinySHT2x_demo_delay.ino b/examples/tinySHT2x_demo_delay/tinySHT2x_demo_delay.ino
new file mode 100644
index 0000000..d90e34f
--- /dev/null
+++ b/examples/tinySHT2x_demo_delay/tinySHT2x_demo_delay.ino
@@ -0,0 +1,33 @@
+//
+//    FILE: tinySHT2x_demo_delay.ino
+//  AUTHOR: Rob Tillaart
+// PURPOSE: demo
+//     URL: https://github.com/RobTillaart/tinySHT2x
+
+
+#include "Wire.h"
+#include "tinySHT2x.h"
+
+tinySHT2x sht;
+
+
+void setup()
+{
+  Serial.begin(115200);
+  Serial.println(__FILE__);
+
+  Wire.begin();
+  sht.begin();
+}
+
+
+void loop()
+{
+  Serial.print(sht.getTemperature(65));  //  adjust delay if needed
+  Serial.print("\t");
+  Serial.println(sht.getHumidity(28));  //  adjust delay if needed
+  delay(1000);
+}
+
+
+//  -- END OF FILE --
diff --git a/keywords.txt b/keywords.txt
index 58935f2..230f953 100644
--- a/keywords.txt
+++ b/keywords.txt
@@ -7,9 +7,16 @@ tinySHT2x	KEYWORD1
 
 # Methods and Functions (KEYWORD2)
 begin	KEYWORD2
+isConnected	KEYWORD2
+reset	KEYWORD2
+
+requestTemperature	KEYWORD2
+requestHumidity	KEYWORD2
+readTemperature	KEYWORD2
+readHumidity	KEYWORD2
+
 getTemperature	KEYWORD2
 getHumidity	KEYWORD2
-reset	KEYWORD2
 
 
 # Instances (KEYWORD2)
diff --git a/library.json b/library.json
index e5c1559..8c26b96 100644
--- a/library.json
+++ b/library.json
@@ -15,7 +15,7 @@
     "type": "git",
     "url": "https://github.com/RobTillaart/tinySHT2x.git"
   },
-  "version": "0.1.3",
+  "version": "0.2.0",
   "license": "MIT",
   "frameworks": "arduino",
   "platforms": "avr",
diff --git a/library.properties b/library.properties
index 59a32c5..da097b1 100644
--- a/library.properties
+++ b/library.properties
@@ -1,5 +1,5 @@
 name=tinySHT2x
-version=0.1.3
+version=0.2.0
 author=Rob Tillaart <rob.tillaart@gmail.com>
 maintainer=Rob Tillaart <rob.tillaart@gmail.com>
 sentence=Arduino library for the SHT20, SHT21 and SHT25 temperature and humidity sensor. Optimized for AVR tiny.
diff --git a/test/unit_test_001.cpp b/test/unit_test_001.cpp
index 58f9857..fef4f8d 100644
--- a/test/unit_test_001.cpp
+++ b/test/unit_test_001.cpp
@@ -56,16 +56,19 @@ unittest(test_constant)
 unittest(test_constructor)
 {
   tinySHT2x sht;
-  
+
+  Wire.begin();
+
   sht.begin();
   assertTrue(sht.reset());
-  // need godmode for these
-  // assertEqualFloat(TINY_SHT2x_NO_VALUE, sht.getTemperature(), 0.01);
-  // assertEqualFloat(TINY_SHT2x_NO_VALUE, sht.getHumidity(), 0.01);
+  //  need godmode for these
+  //  assertEqualFloat(TINY_SHT2x_NO_VALUE, sht.getTemperature(), 0.01);
+  //  assertEqualFloat(TINY_SHT2x_NO_VALUE, sht.getHumidity(), 0.01);
 }
 
 
 unittest_main()
 
 
-// --------
+//  -- END OF FILE --
+
diff --git a/tinySHT2x.cpp b/tinySHT2x.cpp
index 85a3a32..0842c1a 100644
--- a/tinySHT2x.cpp
+++ b/tinySHT2x.cpp
@@ -1,10 +1,10 @@
 //
-//    FILE: tinytinySHT2x.cpp
+//    FILE: tinySHT2x.cpp
 //  AUTHOR: Rob Tillaart, Viktor Balint
-// VERSION: 0.1.3
+// VERSION: 0.2.0
 //    DATE: 2021-09-27
 // PURPOSE: Arduino library for the SHT2x temperature and humidity sensor optimized for AVR tiny
-//     URL: https://github.com/RobTillaart/tinytinySHT2x
+//     URL: https://github.com/RobTillaart/tinySHT2x
 
 
 
@@ -16,25 +16,46 @@
 #define SHT2x_ADDRESS                       0x40
 
 
-tinySHT2x::tinySHT2x()
+tinySHT2x::tinySHT2x(TwoWire *wire)
 {
+  _wire = wire;
 }
 
 
-void tinySHT2x::begin(TwoWire *wire)
+bool tinySHT2x::begin()
 {
-  _wire = wire;
-  _wire->begin();
+  return isConnected();
+}
+
+
+bool tinySHT2x::isConnected()
+{
+  _wire->beginTransmission(SHT2x_ADDRESS);
+  return (_wire->endTransmission() == 0);
 }
 
 
-float tinySHT2x::getTemperature()
+bool tinySHT2x::reset()
+{
+  return writeCmd(SHT2x_SOFT_RESET);
+}
+
+
+///////////////////////////////////
+//
+//  ASYNC INTERFACE
+//
+void tinySHT2x::requestTemperature()
+{
+  writeCmd(SHT2x_GET_TEMPERATURE_NO_HOLD);
+}
+
+
+float tinySHT2x::readTemperature()
 {
   uint8_t buffer[3];
   uint16_t raw;
 
-  writeCmd(SHT2x_GET_TEMPERATURE_NO_HOLD);
-  delay(70);
   if (readBytes(3, (uint8_t*) &buffer[0], 90) == false)
   {
     return TINY_SHT2x_NO_VALUE;
@@ -47,14 +68,17 @@ float tinySHT2x::getTemperature()
 }
 
 
-float tinySHT2x::getHumidity()
+void tinySHT2x::requestHumidity()
+{
+  writeCmd(SHT2x_GET_HUMIDITY_NO_HOLD);
+}
+
+
+float tinySHT2x::readHumidity()
 {
   uint8_t buffer[3];
   uint16_t raw;
 
-  //  HUMIDITY
-  writeCmd(SHT2x_GET_HUMIDITY_NO_HOLD);
-  delay(30);
   if (readBytes(3, (uint8_t*) &buffer[0], 30) == false)
   {
     return TINY_SHT2x_NO_VALUE;
@@ -67,9 +91,23 @@ float tinySHT2x::getHumidity()
 }
 
 
-bool tinySHT2x::reset()
+///////////////////////////////////
+//
+//  SYNC INTERFACE
+//
+float tinySHT2x::getTemperature(uint8_t del)
 {
-  return writeCmd(SHT2x_SOFT_RESET);
+  requestTemperature();
+  delay(del);
+  return readTemperature();
+}
+
+
+float tinySHT2x::getHumidity(uint8_t del)
+{
+  requestHumidity();
+  delay(del);
+  return readHumidity();
 }
 
 
@@ -77,7 +115,6 @@ bool tinySHT2x::reset()
 //
 //  PRIVATE
 //
-
 bool tinySHT2x::writeCmd(uint8_t cmd)
 {
   _wire->beginTransmission(SHT2x_ADDRESS);
@@ -86,7 +123,7 @@ bool tinySHT2x::writeCmd(uint8_t cmd)
 }
 
 
-bool tinySHT2x::readBytes(uint8_t n, uint8_t *val, uint8_t maxDuration)
+bool tinySHT2x::readBytes(uint8_t n, uint8_t * val, uint8_t maxDuration)
 {
   _wire->requestFrom((uint8_t)SHT2x_ADDRESS, (uint8_t) n);
   uint32_t start = millis();
diff --git a/tinySHT2x.h b/tinySHT2x.h
index c72cb54..3ae6b99 100644
--- a/tinySHT2x.h
+++ b/tinySHT2x.h
@@ -2,17 +2,17 @@
 //
 //    FILE: tinySHT2x.h
 //  AUTHOR: Rob Tillaart, Viktor Balint
-// VERSION: 0.1.3
+// VERSION: 0.2.0
 //    DATE: 2021-09-27
 // PURPOSE: Arduino library for the SHT2x temperature and humidity sensor optimized for AVR tiny
 //     URL: https://github.com/RobTillaart/tinySHT2x
-//
+
 
 
 #include "Arduino.h"
 #include "Wire.h"
 
-#define TINY_SHT2x_LIB_VERSION            (F("0.1.3"))
+#define TINY_SHT2x_LIB_VERSION            (F("0.2.0"))
 
 #define TINY_SHT2x_NO_VALUE               -999
 
@@ -20,16 +20,26 @@
 class tinySHT2x
 {
 public:
-  tinySHT2x();
+  tinySHT2x(TwoWire *wire = &Wire);
 
-  void  begin(TwoWire *wire = &Wire);
+  bool  begin();
+  bool  isConnected();
   bool  reset();
-  float getTemperature();
-  float getHumidity();
+
+  //  ASYNC INTERFACE
+  void  requestTemperature();
+  void  requestHumidity();
+  float readTemperature();
+  float readHumidity();
+  
+  //  SYNC INTERFACE
+  float getTemperature(uint8_t del = 70);
+  float getHumidity(uint8_t del = 30);
+
 
 private:
   bool  writeCmd(uint8_t cmd);
-  bool  readBytes(uint8_t n, uint8_t *val, uint8_t maxDuration);
+  bool  readBytes(uint8_t n, uint8_t * val, uint8_t maxDuration);
   TwoWire* _wire;
 };