From 985713a0289d2fd1bc0b29f0304feea9bee4bbe7 Mon Sep 17 00:00:00 2001
From: rob tillaart <rob.tillaart@gmail.com>
Date: Fri, 14 Jan 2022 20:27:13 +0100
Subject: [PATCH 1/6] add offset functions, refactor

---
 MS5611.cpp                                    |  53 +++++--
 MS5611.h                                      |  19 ++-
 .../MS5611_test_offset/MS5611_test_offset.ino | 134 ++++++++++++++++++
 keywords.txt                                  |   5 +
 library.json                                  |   2 +-
 library.properties                            |   2 +-
 6 files changed, 198 insertions(+), 17 deletions(-)
 create mode 100644 examples/MS5611_test_offset/MS5611_test_offset.ino

diff --git a/MS5611.cpp b/MS5611.cpp
index 26d3032..5c3c611 100644
--- a/MS5611.cpp
+++ b/MS5611.cpp
@@ -2,11 +2,12 @@
 //    FILE: MS5611.cpp
 //  AUTHOR: Rob Tillaart
 //          Erni - testing/fixes
-// VERSION: 0.3.5
+// VERSION: 0.3.6
 // PURPOSE: MS5611 Temperature & Humidity library for Arduino
 //     URL: https://github.com/RobTillaart/MS5611
 //
 //  HISTORY:
+//  0.3.6   2022-01-15  add setOffset functions; minor refactor;
 //  0.3.5   2022-01-13  fix isConnected() for NANO 33 BLE
 //  0.3.4   2021-12-29  fix #16 compilation for MBED
 //  0.3.3   2021-12-25  Update oversampling timings to reduce time spent waiting
@@ -61,12 +62,14 @@
 //
 MS5611::MS5611(uint8_t deviceAddress)
 {
-  _address      = deviceAddress;
-  _samplingRate = OSR_ULTRA_LOW;
-  _temperature  = MS5611_NOT_READ;
-  _pressure     = MS5611_NOT_READ;
-  _result       = MS5611_NOT_READ;
-  _lastRead     = 0;
+  _address           = deviceAddress;
+  _samplingRate      = OSR_ULTRA_LOW;
+  _temperature       = MS5611_NOT_READ;
+  _pressure          = MS5611_NOT_READ;
+  _result            = MS5611_NOT_READ;
+  _lastRead          = 0;
+  _pressureOffset    = 0;
+  _temperatureOffset = 0;
 }
 
 
@@ -105,7 +108,10 @@ bool MS5611::begin(TwoWire * wire)
 bool MS5611::isConnected()
 {
   _wire->beginTransmission(_address);
-  _wire->write(0);                        // needed for NANO 33 BLE
+   #ifdef ARDUINO_ARCH_NRF52840
+   //  needed for NANO 33 BLE
+  _wire->write(0);
+   #endif
   return (_wire->endTransmission() == 0);
 }
 
@@ -113,7 +119,12 @@ bool MS5611::isConnected()
 void MS5611::reset()
 {
   command(MS5611_CMD_RESET);
-  delayMicroseconds(2800);
+  uint32_t start = micros();
+  while (micros() - start < 2800)  // prevent blocking RTOS
+  {
+    yield();
+    delayMicroseconds(10);
+  }
   // constants that were multiplied in read()
   // do this once and you save CPU cycles
   C[0] = 1;
@@ -195,6 +206,21 @@ void MS5611::setOversampling(osr_t samplingRate)
   _samplingRate = (uint8_t) samplingRate;
 }
 
+
+float MS5611::getTemperature() const  
+{
+  if (_temperatureOffset == 0) return _temperature * 0.01; 
+  return _temperature * 0.01 + _temperatureOffset; 
+};
+
+
+float MS5611::getPressure() const
+{
+  if (_pressureOffset == 0) return _pressure * 0.01;
+  return _pressure * 0.01 + _pressureOffset; 
+};
+
+
 /////////////////////////////////////////////////////
 //
 // PRIVATE
@@ -207,7 +233,14 @@ void MS5611::convert(const uint8_t addr, uint8_t bits)
   bits = constrain(bits, 8, 12);
   uint8_t offset = (bits - 8) * 2;
   command(addr + offset);
-  delayMicroseconds(del[offset/2]);
+
+  uint32_t start = micros();
+  uint16_t waitTime = del[offset/2];
+  while (micros() - start < waitTime)  // prevent blocking RTOS
+  {
+    yield();
+    delayMicroseconds(10);
+  }
 }
 
 
diff --git a/MS5611.h b/MS5611.h
index 012652c..342036e 100644
--- a/MS5611.h
+++ b/MS5611.h
@@ -3,7 +3,7 @@
 //    FILE: MS5611.h
 //  AUTHOR: Rob Tillaart
 //          Erni - testing/fixes
-// VERSION: 0.3.5
+// VERSION: 0.3.6
 // PURPOSE: Arduino library for MS5611 temperature and pressure sensor
 //     URL: https://github.com/RobTillaart/MS5611
 
@@ -29,7 +29,8 @@
 //  CS to VCC  ==>  0x76
 //  CS to GND  ==>  0x77
 
-#define MS5611_LIB_VERSION                    (F("0.3.5"))
+
+#define MS5611_LIB_VERSION                    (F("0.3.6"))
 
 
 #define MS5611_READ_OK                        0
@@ -73,15 +74,21 @@ class MS5611
   osr_t    getOversampling() const { return (osr_t) _samplingRate; };
 
   // temperature is in ²C
-  float    getTemperature() const  { return _temperature * 0.01; };
+  float    getTemperature() const;
 
   // pressure is in mBar
-  float    getPressure() const     { return _pressure * 0.01; };
+  float    getPressure() const;
+
+  //  OFFSET - 0.3.6
+  void     setPressureOffset(float offset = 0) { _pressureOffset = offset; };
+  float    getPressureOffset() { return _pressureOffset; };
+  void     setTemperatureOffset(float offset = 0) { _temperatureOffset = offset; };
+  float    getTemperatureOffset() { return _temperatureOffset; };
 
   // to check for failure
   int      getLastResult() const   { return _result; };
 
-  // last time in millis() that the sensor has been read.
+  // last time in millis() when the sensor has been read.
   uint32_t lastRead()              { return _lastRead; };
 
 
@@ -95,6 +102,8 @@ class MS5611
   uint8_t  _samplingRate;
   int32_t  _temperature;
   int32_t  _pressure;
+  float    _pressureOffset;
+  float    _temperatureOffset;
   int      _result;
   float    C[7];
   uint32_t _lastRead;
diff --git a/examples/MS5611_test_offset/MS5611_test_offset.ino b/examples/MS5611_test_offset/MS5611_test_offset.ino
new file mode 100644
index 0000000..e880853
--- /dev/null
+++ b/examples/MS5611_test_offset/MS5611_test_offset.ino
@@ -0,0 +1,134 @@
+//
+//    FILE: MS5611_test_offset.ino
+//  AUTHOR: Rob Tillaart
+// PURPOSE: demo application
+//    DATE: 2022-01-15
+//     URL: https://github.com/RobTillaart/MS5611
+
+
+#include "MS5611.h"
+
+//  BREAKOUT  MS5611  aka  GY63 - see datasheet
+//
+//  SPI    I2C
+//              +--------+
+//  VCC    VCC  | o      |
+//  GND    GND  | o      |
+//         SCL  | o      |
+//  SDI    SDA  | o      |
+//  CSO         | o      |
+//  SDO         | o L    |   L = led
+//          PS  | o    O |   O = opening  PS
+//              +--------+
+//
+//  PS to VCC  ==>  I2C
+//  PS to GND  ==>  SPI
+//  CS to VCC  ==>  0x76
+//  CS to GND  ==>  0x77
+
+MS5611 MS5611(0x76);   // 0x76 = CSB to VCC; 0x77 = CSB to GND
+
+
+uint32_t start, stop;
+
+
+void setup()
+{
+  Serial.begin(115200);
+  while (!Serial);
+
+  Serial.println();
+  Serial.println(__FILE__);
+  Serial.print("MS5611_LIB_VERSION: ");
+  Serial.println(MS5611_LIB_VERSION);
+
+  if (MS5611.begin() == true)
+  {
+    Serial.println("MS5611 found.");
+  }
+  else
+  {
+    Serial.println("MS5611 not found. halt.");
+    while (1)
+    {
+      digitalWrite(LED_BUILTIN, HIGH);
+      delay(1000);
+      digitalWrite(LED_BUILTIN, LOW);
+      delay(1000);
+    }
+  }
+  Serial.println();
+
+  MS5611.setTemperatureOffset(273.15);  // set temp in Kelvin
+  MS5611.setPressureOffset(-1013);      // set pressure relative to 1 ATM
+}
+
+
+/*
+  There are 5 oversampling settings, each corresponding to a different amount of milliseconds
+  The higher the oversampling, the more accurate the reading will be, however the longer it will take.
+  OSR_ULTRA_HIGH -> 8.22 millis
+  OSR_HIGH       -> 4.11 millis
+  OSR_STANDARD   -> 2.1 millis
+  OSR_LOW        -> 1.1 millis
+  OSR_ULTRA_LOW  -> 0.5 millis   Default = backwards compatible
+*/
+void loop()
+{
+  digitalWrite(LED_BUILTIN, HIGH);
+  MS5611.setOversampling(OSR_ULTRA_LOW);
+  test();
+  digitalWrite(LED_BUILTIN, LOW);
+  delay(1000);
+
+  digitalWrite(LED_BUILTIN, HIGH);
+  MS5611.setOversampling(OSR_LOW);
+  test();
+  digitalWrite(LED_BUILTIN, LOW);
+  delay(1000);
+
+  digitalWrite(LED_BUILTIN, HIGH);
+  MS5611.setOversampling(OSR_STANDARD);
+  test();
+  digitalWrite(LED_BUILTIN, LOW);
+  delay(1000);
+
+  digitalWrite(LED_BUILTIN, HIGH);
+  MS5611.setOversampling(OSR_HIGH);
+  test();
+  digitalWrite(LED_BUILTIN, LOW);
+  delay(1000);
+
+  digitalWrite(LED_BUILTIN, HIGH);
+  MS5611.setOversampling(OSR_ULTRA_HIGH);
+  test();
+  digitalWrite(LED_BUILTIN, LOW);
+  delay(1000);
+  Serial.println();
+}
+
+
+void test()
+{
+  start = micros();
+  int result = MS5611.read();
+  stop = micros();
+  if (result != MS5611_READ_OK)
+  {
+    Serial.print("Error in read: ");
+    Serial.println(result);
+  }
+  else
+  {
+    Serial.print("T: ");
+    Serial.print(MS5611.getTemperature(), 2);
+    Serial.print("\tP: ");
+    Serial.print(MS5611.getPressure(), 2);
+    Serial.print("\tt: ");
+    Serial.print(stop - start);
+    Serial.println();
+  }
+}
+
+
+// -- END OF FILE --
diff --git a/keywords.txt b/keywords.txt
index b56c0a7..afc3609 100644
--- a/keywords.txt
+++ b/keywords.txt
@@ -17,6 +17,11 @@ getPressure	KEYWORD2
 getLastResult	KEYWORD2
 lastRead	KEYWORD2
 
+setTemperatureOffset	KEYWORD2
+getTemperatureOffset	KEYWORD2
+setPressureOffset	KEYWORD2
+getPressureOffset	KEYWORD2
+
 
 # Instances (KEYWORD2)
 
diff --git a/library.json b/library.json
index f4dcd41..8bd23a6 100644
--- a/library.json
+++ b/library.json
@@ -18,7 +18,7 @@
     "type": "git",
     "url": "https://github.com/RobTillaart/MS5611.git"
   },
-  "version": "0.3.5",
+  "version": "0.3.6",
   "license": "MIT",
   "frameworks": "arduino",
   "platforms": "*",
diff --git a/library.properties b/library.properties
index e87f01b..caab8e3 100644
--- a/library.properties
+++ b/library.properties
@@ -1,5 +1,5 @@
 name=MS5611
-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 MS5611 temperature and pressure sensor

From 91663b1cfc833c4fa7733e71fd8c62e69dd1731a Mon Sep 17 00:00:00 2001
From: rob tillaart <rob.tillaart@gmail.com>
Date: Fri, 14 Jan 2022 20:44:03 +0100
Subject: [PATCH 2/6] add offset functions, refactor

---
 README.md | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/README.md b/README.md
index ab69b43..6490d38 100644
--- a/README.md
+++ b/README.md
@@ -77,7 +77,21 @@ See table below and test example how to use.
 - **uint32_t lastRead()** last time when **read()** was called in milliseconds since startup.
 
 
-#### Oversampling table
+### Offset
+
+The offset functions are added to calibrate the sensor against e.g. local weather station. This calibration can only be done runtime.
+
+- **void setPressureOffset(float offset = 0)** Set an offset to calibrate the pressure. 
+Can also be used to get the pressure relative to e.g. 1 Atm. (set offset to -1013 HPa).
+Default the value is set to 0.
+- **float getPressureOffset()** returns the current pressure offset.
+- **void setTemperatureOffset(float offset = 0)** Set an offset to calibrate the temperature. 
+Can also be used to get the temperature in degrees Kelvin. (set offset to +273.15)
+Default the value is set to 0.
+- **float getTemperatureOffset()** returns the current temperature offset.
+
+
+### Oversampling table
 
 (numbers from datasheet, actual time differs - todo)
 

From 20b1b61da78bf8685fe9e35323ae951e39b50307 Mon Sep 17 00:00:00 2001
From: rob tillaart <rob.tillaart@gmail.com>
Date: Sat, 15 Jan 2022 12:32:46 +0100
Subject: [PATCH 3/6] refactor

---
 MS5611.cpp         | 43 ++++++++++++---------
 MS5611.h           | 15 ++++----
 README.md          | 93 ++++++++++++++++++++++++++++------------------
 library.json       |  2 +-
 library.properties |  2 +-
 5 files changed, 92 insertions(+), 63 deletions(-)

diff --git a/MS5611.cpp b/MS5611.cpp
index 5c3c611..6a232a8 100644
--- a/MS5611.cpp
+++ b/MS5611.cpp
@@ -120,7 +120,8 @@ void MS5611::reset()
 {
   command(MS5611_CMD_RESET);
   uint32_t start = micros();
-  while (micros() - start < 2800)  // prevent blocking RTOS
+  // while loop prevents blocking RTOS
+  while (micros() - start < 2800)
   {
     yield();
     delayMicroseconds(10);
@@ -227,16 +228,20 @@ float MS5611::getPressure() const
 //
 void MS5611::convert(const uint8_t addr, uint8_t bits)
 {
-  //Values from page 2 datasheet
+  // values from page 2 datasheet
   uint16_t del[5] = {500, 1100, 2100, 4100, 8220};
 
-  bits = constrain(bits, 8, 12);
-  uint8_t offset = (bits - 8) * 2;
+  uint8_t index = bits;
+  if (index < 8) index = 8;
+  else if (index > 12) index = 12;
+  index -= 8;
+  uint8_t offset = index * 2;
   command(addr + offset);
 
+  uint16_t waitTime = del[index];
   uint32_t start = micros();
-  uint16_t waitTime = del[offset/2];
-  while (micros() - start < waitTime)  // prevent blocking RTOS
+  // while loop prevents blocking RTOS
+  while (micros() - start < waitTime)
   {
     yield();
     delayMicroseconds(10);
@@ -246,7 +251,7 @@ void MS5611::convert(const uint8_t addr, uint8_t bits)
 
 uint16_t MS5611::readProm(uint8_t reg)
 {
-  // last EEPROM register is CRC - Page13 datasheet.
+  // last EEPROM register is CRC - Page 13 datasheet.
   uint8_t promCRCRegister = 7;
   if (reg > promCRCRegister) return 0;
 
@@ -254,12 +259,13 @@ uint16_t MS5611::readProm(uint8_t reg)
   command(MS5611_CMD_READ_PROM + offset);
   if (_result == 0)
   {
-    int nr = _wire->requestFrom(_address, (uint8_t)2);
-    if (nr >= 2)
+    uint8_t length = 2;
+    int bytes = _wire->requestFrom(_address, length);
+    if (bytes >= length)
     {
-      uint16_t val = _wire->read() * 256;
-      val += _wire->read();
-      return val;
+      uint16_t value = _wire->read() * 256;
+      value += _wire->read();
+      return value;
     }
     return 0;
   }
@@ -272,13 +278,14 @@ uint32_t MS5611::readADC()
   command(MS5611_CMD_READ_ADC);
   if (_result == 0)
   {
-    int nr = _wire->requestFrom(_address, (uint8_t)3);
-    if (nr >= 3)
+    uint8_t length = 3;
+    int bytes = _wire->requestFrom(_address, length);
+    if (bytes >= length)
     {
-      uint32_t val = _wire->read() * 65536UL;
-      val += _wire->read() * 256UL;
-      val += _wire->read();
-      return val;
+      uint32_t value = _wire->read() * 65536UL;
+      value += _wire->read() * 256UL;
+      value += _wire->read();
+      return value;
     }
     return 0UL;
   }
diff --git a/MS5611.h b/MS5611.h
index 342036e..7964edf 100644
--- a/MS5611.h
+++ b/MS5611.h
@@ -21,7 +21,7 @@
 //  SDI    SDA  | o      |
 //  CSO         | o      |
 //  SDO         | o L    |   L = led
-//          PS  | o    O |   O = opening  PS
+//          PS  | o    O |   O = opening  PS = protocol select
 //              +--------+
 //
 //  PS to VCC  ==>  I2C
@@ -40,11 +40,11 @@
 
 enum osr_t
 {
-    OSR_ULTRA_HIGH = 12, // 10 millis
-    OSR_HIGH       = 11, //  5 millis
-    OSR_STANDARD   = 10, //  3 millis
-    OSR_LOW        = 9,  //  2 millis
-    OSR_ULTRA_LOW  = 8   //  1 millis    Default = backwards compatible
+    OSR_ULTRA_HIGH = 12,        // 10 millis
+    OSR_HIGH       = 11,        //  5 millis
+    OSR_STANDARD   = 10,        //  3 millis
+    OSR_LOW        = 9,         //  2 millis
+    OSR_ULTRA_LOW  = 8          //  1 millis    Default = backwards compatible
 };
 
 
@@ -65,7 +65,8 @@ class MS5611
   // the actual reading of the sensor;
   // returns MS5611_READ_OK upon success
   int      read(uint8_t bits);
-  inline int read() { return read( (uint8_t) _samplingRate); };  // uses the preset oversampling
+  // wrapper, uses the preset oversampling rate.
+  inline int read() { return read( (uint8_t) _samplingRate); };
 
   // sets oversampling to a value between 8 and 12
   void     setOversampling(osr_t samplingRate);
diff --git a/README.md b/README.md
index 6490d38..08accdb 100644
--- a/README.md
+++ b/README.md
@@ -13,13 +13,16 @@ Arduino library for MS5611 temperature and pressure sensor.
 
 ## Description
 
-The MS5611 is a high resolution temperature and pressure sensor.
-The high resolution is made possible by oversampling (many times).
+The MS5611 is a high resolution temperature and pressure sensor a.k.a GY-63.
+The high resolution is made possible by oversampling many times.
 
-The device address is 0x76 or 0x77 depending on the CSB pin.
+The device address is 0x76 or 0x77 depending on the CSB/CSO pin.
 
 This library only implements the I2C interface. 
 
+
+#### breakout
+
 ```cpp
 //
 //  BREAKOUT  MS5611  aka  GY63 - see datasheet
@@ -32,7 +35,7 @@ This library only implements the I2C interface.
 //  SDI    SDA  | o      |
 //  CSO         | o      |
 //  SDO         | o L    |   L = led
-//          PS  | o    O |   O = opening  PS
+//          PS  | o    O |   O = opening  PS = protocol select
 //              +--------+
 //
 //  PS to VCC  ==>  I2C
@@ -42,7 +45,14 @@ This library only implements the I2C interface.
 //
 ```
 
-## important Changes
+#### related libraries
+
+For pressure conversions see - https://github.com/RobTillaart/pressure
+
+For temperature conversions see - https://github.com/RobTillaart/Temperature
+
+
+## Release Notes
 
 #### 0.3.0 breaking change
 
@@ -53,45 +63,40 @@ This library only implements the I2C interface.
 
 #### 0.3.5 NANO 33 BLE
 
-After lots of hours of testing it appeared that the I2C/Wire library of the NANO 33 BLE
+The I2C/Wire library of the NANO 33 BLE does not see the device on the I2C bus. 
+After hours of testing it looks like that the I2C/Wire library of the NANO 33 BLE 
 does not handle **isConnected()** like other platforms do. 
-It looks like an uninitialized length of the I2C buffer, causing failure when calling **begin()**.
-Adding a **wire->write(0x00)** seems to fix the issue.
+Adding a **wire->write(0x00)** in **isConnected()** fixes the problem, 
+however more investigation is needed to understand the root cause.
+In 0.3.6 this **write(0)** is made conditional explicit for the NANO 33 BLE.
 
 
 ## Interface
 
+#### Base
+
 - **MS5611(uint8_t deviceAddress)** constructor.
 - **bool begin(uint8_t sda, uint8_t scl, TwoWire \*wire = &Wire)** for ESP and alike, optionally set Wire interface. initializes internals, 
 - **bool begin(TwoWire \*wire = &Wire)** for UNO and alike, optionally set Wire interface. Initializes internals.
 - **bool isConnected()** checks availability of device address on the I2C bus.
+(see note above NANO 33 BLE).
 - **reset()** resets the chip and loads constants from its ROM.
-- **int read(uint8_t bits)** the actual reading of the sensor. Returns MS5611_READ_OK upon success.
-- **int read()** the actual reading of the sensor, uses the preset oversampling (see below). Returns MS5611_READ_OK upon success.
-- **void setOversampling(osr_t samplingRate)** sets the amount of oversampling. 
-See table below and test example how to use.
-- **osr_t getOversampling()** returns amount of oversampling.
-- **float getTemperature()** returns temperature in °C. Subsequent calls will return same value until a new **read()** is called.
-- **float getPressure()** pressure is in mBar. Subsequent calls will return same value until a new **read()** is called.
-- **int getLastResult()** checks last I2C communication (replace with more informative error handling?)
-- **uint32_t lastRead()** last time when **read()** was called in milliseconds since startup.
-
+- **int read(uint8_t bits)** the actual reading of the sensor. 
+Number of bits determines the oversampling factor. Returns MS5611_READ_OK upon success.
+- **int read()** wraps the **read()** above, uses the preset oversampling (see below). 
+Returns MS5611_READ_OK upon success.
+- **float getTemperature()** returns temperature in °C. 
+Subsequent calls will return the same value until a new **read()** is called.
+- **float getPressure()** pressure is in mBar. 
+Subsequent calls will return the same value until a new **read()** is called.
 
-### Offset
 
-The offset functions are added to calibrate the sensor against e.g. local weather station. This calibration can only be done runtime.
-
-- **void setPressureOffset(float offset = 0)** Set an offset to calibrate the pressure. 
-Can also be used to get the pressure relative to e.g. 1 Atm. (set offset to -1013 HPa).
-Default the value is set to 0.
-- **float getPressureOffset()** returns the current pressure offset.
-- **void setTemperatureOffset(float offset = 0)** Set an offset to calibrate the temperature. 
-Can also be used to get the temperature in degrees Kelvin. (set offset to +273.15)
-Default the value is set to 0.
-- **float getTemperatureOffset()** returns the current temperature offset.
+#### Oversampling
 
+- **void setOversampling(osr_t samplingRate)** sets the amount of oversampling. 
+See table below and test example how to use.
+- **osr_t getOversampling()** returns amount of oversampling.
 
-### Oversampling table
 
 (numbers from datasheet, actual time differs - todo)
 
@@ -104,9 +109,26 @@ Default the value is set to 0.
 | OSR_ULTRA_LOW  |  8    |        256         |      0.065       |   0.5     | Default = backwards compatible
 
 
-## Disclaimer
+#### Offset 
 
-The library is still experimental. So all feedback is welcome.
+The offset functions are added (0.3.6) to calibrate the sensor against e.g. a local weather station. 
+This calibration can only be done runtime.
+
+- **void setPressureOffset(float offset = 0)** Set an offset to calibrate the pressure. 
+Can be used to get the pressure relative to e.g. 1 Atm. 
+Set the offset to -1013 HPa/mBar and you get a sort of relative pressure.
+Default the offset is set to 0.
+- **float getPressureOffset()** returns the current pressure offset.
+- **void setTemperatureOffset(float offset = 0)** Set an offset to calibrate the temperature. 
+Can be used to get the temperature in degrees Kelvin, just set the offset to +273.15.
+Default the offset is set to 0.
+- **float getTemperatureOffset()** returns the current temperature offset.
+
+
+#### Misc
+
+- **int getLastResult()** checks last I2C communication. Replace with more informative error handling?
+- **uint32_t lastRead()** last time when **read()** was called in milliseconds since startup.
 
 
 ## Operation
@@ -117,11 +139,10 @@ See examples
 ## Future
 
 - update documentation
+  - separate release notes?
 - create a SPI based library (same base class if possible?)
-  - first get it working 100%
+  - first get this lib working 100%
 - proper error handling
 - redo lower level functions?
 - handle the read + math of temperature first? 
-- add get- and setPressureOffset()
-- add get- and setTemperatureOffset()
-
+-
diff --git a/library.json b/library.json
index 8bd23a6..8f42149 100644
--- a/library.json
+++ b/library.json
@@ -1,6 +1,6 @@
 {
   "name": "MS5611",
-  "keywords": "MS5611,temperature,pressure",
+  "keywords": "MS5611,GY-63,GY63,temperature,pressure",
   "description": "Arduino library for MS5611 temperature and pressure sensor",
   "authors":
   [
diff --git a/library.properties b/library.properties
index caab8e3..723be85 100644
--- a/library.properties
+++ b/library.properties
@@ -3,7 +3,7 @@ version=0.3.6
 author=Rob Tillaart <rob.tillaart@gmail.com>
 maintainer=Rob Tillaart <rob.tillaart@gmail.com>
 sentence=Arduino library for MS5611 temperature and pressure sensor
-paragraph=Experimental
+paragraph=Experimental, GY-63, GY63.
 category=Sensors
 url=https://github.com/RobTillaart/MS5611
 architectures=*

From e3d1b442592213687da8a41fbf6c6ccabdfd93cc Mon Sep 17 00:00:00 2001
From: rob tillaart <rob.tillaart@gmail.com>
Date: Sat, 15 Jan 2022 16:08:15 +0100
Subject: [PATCH 4/6] update convert timing - use MAX - issue 23

---
 MS5611.cpp |  5 +++--
 README.md  | 20 +++++++++++---------
 2 files changed, 14 insertions(+), 11 deletions(-)

diff --git a/MS5611.cpp b/MS5611.cpp
index 6a232a8..c1bb7bc 100644
--- a/MS5611.cpp
+++ b/MS5611.cpp
@@ -8,6 +8,7 @@
 //
 //  HISTORY:
 //  0.3.6   2022-01-15  add setOffset functions; minor refactor;
+//                      adjust convert timing to max - see issue #23
 //  0.3.5   2022-01-13  fix isConnected() for NANO 33 BLE
 //  0.3.4   2021-12-29  fix #16 compilation for MBED
 //  0.3.3   2021-12-25  Update oversampling timings to reduce time spent waiting
@@ -228,8 +229,8 @@ float MS5611::getPressure() const
 //
 void MS5611::convert(const uint8_t addr, uint8_t bits)
 {
-  // values from page 2 datasheet
-  uint16_t del[5] = {500, 1100, 2100, 4100, 8220};
+  // values from page 3 datasheet - MAX column (rounded up)
+  uint16_t del[5] = {600, 1200, 2300, 4600, 9100};
 
   uint8_t index = bits;
   if (index < 8) index = 8;
diff --git a/README.md b/README.md
index 08accdb..215adb9 100644
--- a/README.md
+++ b/README.md
@@ -98,15 +98,17 @@ See table below and test example how to use.
 - **osr_t getOversampling()** returns amount of oversampling.
 
 
-(numbers from datasheet, actual time differs - todo)
-
-| definition     | value | oversampling ratio | resolution (mbar) | time (ms) | notes |
-|:--------------:|:-----:|:------------------:|:----------------:|:---------:|:------:|
-| OSR_ULTRA_HIGH |  12   |        4096        |      0.012       |   8.22    |
-| OSR_HIGH       |  11   |        2048        |      0.018       |   4.1     |
-| OSR_STANDARD   |  10   |        1024        |      0.027       |   2.1     |
-| OSR_LOW        |  9    |        512         |      0.042       |   1.1     |
-| OSR_ULTRA_LOW  |  8    |        256         |      0.065       |   0.5     | Default = backwards compatible
+Some numbers from datasheet, page 3 MAX column rounded up. (see #23)
+(actual read time differs - see performance sketch)
+
+| definition     | value | oversampling ratio | resolution (mbar) | time (us) | notes  |
+|:--------------:|:-----:|:------------------:|:-----------------:|:---------:|:------:|
+| OSR_ULTRA_HIGH |  12   |        4096        |      0.012        |   9100    |
+| OSR_HIGH       |  11   |        2048        |      0.018        |   4600    |
+| OSR_STANDARD   |  10   |        1024        |      0.027        |   2300    |
+| OSR_LOW        |  9    |        512         |      0.042        |   1200    |
+| OSR_ULTRA_LOW  |  8    |        256         |      0.065        |    600    | Default = backwards compatible
+
 
 
 #### Offset 

From a083e9236e14e92ac44fbde50347b0d63984402d Mon Sep 17 00:00:00 2001
From: rob tillaart <rob.tillaart@gmail.com>
Date: Sat, 15 Jan 2022 16:34:09 +0100
Subject: [PATCH 5/6] update convert timing - use MAX - issue 23

---
 MS5611.cpp                                   |   8 +-
 MS5611.h                                     |  12 ++-
 README.md                                    |   8 +-
 examples/MS5611_test_two/MS5611_test_two.ino | 106 +++++++++++++++++++
 4 files changed, 126 insertions(+), 8 deletions(-)
 create mode 100644 examples/MS5611_test_two/MS5611_test_two.ino

diff --git a/MS5611.cpp b/MS5611.cpp
index c1bb7bc..f66543c 100644
--- a/MS5611.cpp
+++ b/MS5611.cpp
@@ -209,17 +209,17 @@ void MS5611::setOversampling(osr_t samplingRate)
 }
 
 
-float MS5611::getTemperature() const  
+float MS5611::getTemperature() const
 {
-  if (_temperatureOffset == 0) return _temperature * 0.01; 
-  return _temperature * 0.01 + _temperatureOffset; 
+  if (_temperatureOffset == 0) return _temperature * 0.01;
+  return _temperature * 0.01 + _temperatureOffset;
 };
 
 
 float MS5611::getPressure() const
 {
   if (_pressureOffset == 0) return _pressure * 0.01;
-  return _pressure * 0.01 + _pressureOffset; 
+  return _pressure * 0.01 + _pressureOffset;
 };
 
 
diff --git a/MS5611.h b/MS5611.h
index 7964edf..abed9b1 100644
--- a/MS5611.h
+++ b/MS5611.h
@@ -81,8 +81,8 @@ class MS5611
   float    getPressure() const;
 
   //  OFFSET - 0.3.6
-  void     setPressureOffset(float offset = 0) { _pressureOffset = offset; };
-  float    getPressureOffset() { return _pressureOffset; };
+  void     setPressureOffset(float offset = 0)    { _pressureOffset = offset; };
+  float    getPressureOffset()    { return _pressureOffset; };
   void     setTemperatureOffset(float offset = 0) { _temperatureOffset = offset; };
   float    getTemperatureOffset() { return _temperatureOffset; };
 
@@ -90,7 +90,13 @@ class MS5611
   int      getLastResult() const   { return _result; };
 
   // last time in millis() when the sensor has been read.
-  uint32_t lastRead()              { return _lastRead; };
+  uint32_t lastRead() const        { return _lastRead; };
+
+  // develop functions.
+  /*
+  void     setAddress(uint8_t address) { _address = address; };  // RANGE CHECK !!!
+  uint8_t  getAddress() const          { return _address; };
+  */
 
 
 private:
diff --git a/README.md b/README.md
index 215adb9..c6a59e8 100644
--- a/README.md
+++ b/README.md
@@ -68,7 +68,13 @@ After hours of testing it looks like that the I2C/Wire library of the NANO 33 BL
 does not handle **isConnected()** like other platforms do. 
 Adding a **wire->write(0x00)** in **isConnected()** fixes the problem, 
 however more investigation is needed to understand the root cause.
-In 0.3.6 this **write(0)** is made conditional explicit for the NANO 33 BLE.
+
+
+#### 0.3.6 
+
+The **write(0)** in **isConnected()** is made conditional explicit for the NANO 33 BLE.
+
+The timing for convert is adjusted from TYPICAL to MAX - datasheet page 3.
 
 
 ## Interface
diff --git a/examples/MS5611_test_two/MS5611_test_two.ino b/examples/MS5611_test_two/MS5611_test_two.ino
new file mode 100644
index 0000000..9eac6fc
--- /dev/null
+++ b/examples/MS5611_test_two/MS5611_test_two.ino
@@ -0,0 +1,106 @@
+//
+//    FILE: MS5611_test_two.ino
+//  AUTHOR: Rob Tillaart
+// PURPOSE: demo application for two sensors
+//    DATE: 2022-01-15
+//     URL: https://github.com/RobTillaart/MS5611
+
+
+#include "MS5611.h"
+
+//  BREAKOUT  MS5611  aka  GY63 - see datasheet
+//
+//  SPI    I2C
+//              +--------+
+//  VCC    VCC  | o      |
+//  GND    GND  | o      |
+//         SCL  | o      |
+//  SDI    SDA  | o      |
+//  CSO         | o      |
+//  SDO         | o L    |   L = led
+//          PS  | o    O |   O = opening  PS
+//              +--------+
+//
+//  PS to VCC  ==>  I2C
+//  PS to GND  ==>  SPI
+//  CS to VCC  ==>  0x76
+//  CS to GND  ==>  0x77
+
+
+MS5611 ONE(0x76);   // 0x76 = CSB to VCC
+MS5611 TWO(0x77);   // 0x77 = CSB to GND
+
+
+uint32_t start, stop;
+
+
+void setup()
+{
+  Serial.begin(115200);
+  while (!Serial);
+
+  Serial.println();
+  Serial.println(__FILE__);
+  Serial.print("MS5611_LIB_VERSION: ");
+  Serial.println(MS5611_LIB_VERSION);
+
+  if (ONE.begin() == true)
+  {
+    Serial.println("MS5611 0x76 found.");
+  }
+  else
+  {
+    Serial.println("MS5611 0x76 not found.");
+  }
+
+  if (TWO.begin() == true)
+  {
+    Serial.println("MS5611 0x77 found.");
+  }
+  else
+  {
+    Serial.println("MS5611 0x77 not found.");
+  }
+
+}
+
+
+void loop()
+{
+  digitalWrite(LED_BUILTIN, HIGH);
+  int result = ONE.read();
+  stop = micros();
+  if (result != MS5611_READ_OK)
+  {
+    Serial.print("0x76 Error in read: ");
+    Serial.println(result);
+  }
+
+  result = TWO.read();
+  stop = micros();
+  if (result != MS5611_READ_OK)
+  {
+    Serial.print("0x77 Error in read: ");
+    Serial.println(result);
+  }
+  digitalWrite(LED_BUILTIN, LOW);
+
+  Serial.print("T: ");
+  Serial.print(ONE.getTemperature(), 2);
+  Serial.print("\tP: ");
+  Serial.print(ONE.getPressure(), 2);
+  Serial.print("\tT: ");
+  Serial.print(TWO.getTemperature(), 2);
+  Serial.print("\tP: ");
+  Serial.print(TWO.getPressure(), 2);
+  Serial.print("\tT: ");
+  Serial.print(ONE.getTemperature() - TWO.getTemperature(), 2);
+  Serial.print("\tP: ");
+  Serial.print(ONE.getPressure() - TWO.getPressure(), 2);
+  Serial.println();
+
+  delay(1000);
+}
+
+
+// -- END OF FILE --

From ea068c7d56354cba0de9f9d0442f8b646a0cec07 Mon Sep 17 00:00:00 2001
From: rob tillaart <rob.tillaart@gmail.com>
Date: Sat, 15 Jan 2022 20:31:53 +0100
Subject: [PATCH 6/6] fixes

---
 examples/MS5611_test/MS5611_test.ino          |  2 +
 .../MS5611_test_offset/MS5611_test_offset.ino |  2 +
 .../MS5611_test_plotter.ino                   | 72 +++++++++++++++++++
 examples/MS5611_test_two/MS5611_test_two.ino  |  2 +
 4 files changed, 78 insertions(+)
 create mode 100644 examples/MS5611_test_plotter/MS5611_test_plotter.ino

diff --git a/examples/MS5611_test/MS5611_test.ino b/examples/MS5611_test/MS5611_test.ino
index c877a13..4697662 100644
--- a/examples/MS5611_test/MS5611_test.ino
+++ b/examples/MS5611_test/MS5611_test.ino
@@ -37,6 +37,8 @@ void setup()
   Serial.begin(115200);
   while (!Serial);
 
+  pinMode(LED_BUILTIN, OUTPUT);
+
   Serial.println();
   Serial.println(__FILE__);
   Serial.print("MS5611_LIB_VERSION: ");
diff --git a/examples/MS5611_test_offset/MS5611_test_offset.ino b/examples/MS5611_test_offset/MS5611_test_offset.ino
index e880853..70da060 100644
--- a/examples/MS5611_test_offset/MS5611_test_offset.ino
+++ b/examples/MS5611_test_offset/MS5611_test_offset.ino
@@ -37,6 +37,8 @@ void setup()
   Serial.begin(115200);
   while (!Serial);
 
+  pinMode(LED_BUILTIN, OUTPUT);
+
   Serial.println();
   Serial.println(__FILE__);
   Serial.print("MS5611_LIB_VERSION: ");
diff --git a/examples/MS5611_test_plotter/MS5611_test_plotter.ino b/examples/MS5611_test_plotter/MS5611_test_plotter.ino
new file mode 100644
index 0000000..3742acb
--- /dev/null
+++ b/examples/MS5611_test_plotter/MS5611_test_plotter.ino
@@ -0,0 +1,72 @@
+//
+//    FILE: MS5611_test_plotter.ino
+//  AUTHOR: Rob Tillaart
+// PURPOSE: demo application
+//    DATE: 2022-01-15
+//     URL: https://github.com/RobTillaart/MS5611
+
+
+#include "MS5611.h"
+
+//  BREAKOUT  MS5611  aka  GY63 - see datasheet
+//
+//  SPI    I2C
+//              +--------+
+//  VCC    VCC  | o      |
+//  GND    GND  | o      |
+//         SCL  | o      |
+//  SDI    SDA  | o      |
+//  CSO         | o      |
+//  SDO         | o L    |   L = led
+//          PS  | o    O |   O = opening  PS
+//              +--------+
+//
+//  PS to VCC  ==>  I2C
+//  PS to GND  ==>  SPI
+//  CS to VCC  ==>  0x76
+//  CS to GND  ==>  0x77
+
+MS5611 MS5611(0x76);   // 0x76 = CSB to VCC; 0x77 = CSB to GND
+
+void setup()
+{
+  Serial.begin(115200);
+  while (!Serial);
+
+  pinMode(LED_BUILTIN, OUTPUT);
+
+  Serial.println();
+  if (MS5611.begin() == true)
+  {
+    Serial.println("MS5611 found.");
+  }
+  else
+  {
+    Serial.println("MS5611 not found. halt.");
+    while (1)
+    {
+      digitalWrite(LED_BUILTIN, HIGH);
+      delay(1000);
+      digitalWrite(LED_BUILTIN, LOW);
+      delay(1000);
+    }
+  }
+  Serial.println("TEMP\tPRESSURE");
+  // scale T & P to same range :)
+  MS5611.setPressureOffset(-1000);
+}
+
+void loop()
+{
+  digitalWrite(LED_BUILTIN, HIGH);
+  MS5611.read();
+  Serial.print(MS5611.getTemperature(), 2);
+  Serial.print("\t");
+  Serial.print(MS5611.getPressure(), 2);
+  Serial.println();
+  digitalWrite(LED_BUILTIN, LOW);
+  delay(1000);
+}
+
+
+// -- END OF FILE --
diff --git a/examples/MS5611_test_two/MS5611_test_two.ino b/examples/MS5611_test_two/MS5611_test_two.ino
index 9eac6fc..abd4a64 100644
--- a/examples/MS5611_test_two/MS5611_test_two.ino
+++ b/examples/MS5611_test_two/MS5611_test_two.ino
@@ -39,6 +39,8 @@ void setup()
   Serial.begin(115200);
   while (!Serial);
 
+  pinMode(LED_BUILTIN, OUTPUT);
+
   Serial.println();
   Serial.println(__FILE__);
   Serial.print("MS5611_LIB_VERSION: ");