From 8a063e7c277c7240e1123cf24643f96c837c457b Mon Sep 17 00:00:00 2001
From: Christoph Schultz <ic-schultz@gmx.de>
Date: Thu, 14 Jan 2021 22:28:47 +0100
Subject: [PATCH] Add support for setting the range and autocalibration. Closes
 #1.

* added possibility to set Range, to enable/disable Autocalibrate and to calibrate maually ( see Datasheet v 1.2 : https://www.winsen-sensor.com/d/files/MH-Z14A.pdf

* Update MHZ.cpp

* Update MHZ.cpp

* Update MHZ.h

added calibrate Span, for complete functionality but commented out , due to professional use (req. constant atmosphere with 2k, 5k or 10k ppm CO2.).
corrected the bugs in MHZ.cpp also.

* Update MHZ.cpp

Added comments for  Sensors with specific firmware.

Co-authored-by: Christoph Schultz <christoph@schultz1-christoph.de>
---
 MHZ.cpp | 70 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 MHZ.h   |  8 ++++++-
 2 files changed, 77 insertions(+), 1 deletion(-)

diff --git a/MHZ.cpp b/MHZ.cpp
index 7c01714..6251b88 100644
--- a/MHZ.cpp
+++ b/MHZ.cpp
@@ -7,6 +7,9 @@
 
 const int MHZ14A = 14;
 const int MHZ19B = 19;
+const int MHZ_2K = 1;
+const int MHZ_5K = 2;
+const int MHZ_10K = 3;
 
 const unsigned long MHZ14A_PREHEATING_TIME = 3L * 60L * 1000L;
 const unsigned long MHZ19B_PREHEATING_TIME = 3L * 60L * 1000L;
@@ -251,3 +254,70 @@ int MHZ::readCO2PWM() {
   }
   return ppm_pwm;
 }
+
+void MHZ::setAutoCalibrate(boolean b)  //only available for MHZ-19B with firmware < 1.6 and MHZ 14a
+{
+  uint8_t cmd_enableAutoCal[9] = { 0xFF, 0x01, 0x79, 0xA0, 0x00, 0x00, 0x00, 0x00, 0xE6 };
+  uint8_t cmd_disableAutoCal[9] = { 0xFF, 0x01, 0x79, 0x00, 0x00, 0x00, 0x00, 0x00, 0x86};
+  if (b)
+  {
+  _serial->write(cmd_enableAutoCal,9);
+   }
+  else
+  {
+    _serial->write(cmd_disableAutoCal,9);
+  }
+}
+
+void MHZ::setRange(int range) //only available for MHZ-19B < 1.6 and MH-Z 14a
+{ 
+   uint8_t cmd_2K[9] = {0xFF, 0x01, 0x99, 0x00, 0x00, 0x00, 0x07, 0xD0, 0x8F}; 
+  uint8_t cmd_5K[9] = {0xFF, 0x01, 0x99, 0x00, 0x00, 0x00, 0x13, 0x88, 0xCB};
+  uint8_t cmd_10K[9] = {0xFF, 0x01, 0x99, 0x00, 0x00, 0x00, 0x27, 0x10, 0x2F};
+    
+  switch(range)
+  {
+    case 1:
+      _serial->write(cmd_2K,9);
+      break;
+    case 2:
+      _serial->write(cmd_5K,9);
+      break;
+    case 3: 
+      _serial->write(cmd_10K,9);
+    
+  }
+}
+
+void MHZ::calibrateZero()
+{
+  char cmd[9] = {0xFF, 0x01, 0x87, 0x00, 0x00, 0x00, 0x00, 0x00, 0x78};
+  _serial->write(cmd,9);
+}
+
+/***** calibrateSpan() function for professional use. requires a constant atmosphere with 2K, 5k or 10k ppm CO2 and calibrateZero at first.
+
+void MHZ::calibrateSpan(int range)
+{
+    char cmd_2K[9] = {0xFF, 0x01, 0x88, 0x07, 0xD0, 0x00, 0x00, 0x00, 0xA0};
+    char cmd_5K[9] = {oxFF, 0x01, 0x88, 0x13, 0x88, 0x00, 0x00, 0x00, 0xDC};
+    char cmd_10K[9]= {0xFF, 0x01, 0x88, 0x27, 0x10, 0x00, 0x00, 0x00, 0x40};
+    
+    switch(range)
+    {
+        case 1:
+            _serial->write(cmd_2K,9);
+            break;
+        case 2:
+            _serial->write(cmd_5K,9);
+            break;
+        case 3:
+             _serial->write(cmd_10k,9);
+      }
+      
+  }
+  ****/
+           
+        
+    
+    
diff --git a/MHZ.h b/MHZ.h
index cd2c2fb..e03c67a 100644
--- a/MHZ.h
+++ b/MHZ.h
@@ -16,7 +16,9 @@
 // types of sensors.
 extern const int MHZ14A;
 extern const int MHZ19B;
-
+extern const int MHZ_2K;
+extern const int MHZ_5k;
+extern const int MHZ_10K;
 // status codes
 extern const int STATUS_NO_RESPONSE;
 extern const int STATUS_CHECKSUM_MISMATCH;
@@ -35,6 +37,10 @@ class MHZ {
 
   boolean isPreHeating();
   boolean isReady();
+  void setAutoCalibrate(boolean b);
+  void calibrateZero();
+  void setRange(int range);
+ // void calibrateSpan(int range); //only for professional use... see implementation and Dataheet.
 
   int readCO2UART();
   int readCO2PWM();