From 1ff821d8866f6c2c95ad2dcfd4a97a97d1886eaa Mon Sep 17 00:00:00 2001
From: gemu2015 <gmutz2010@googlemail.com>
Date: Sat, 18 May 2019 13:23:55 +0200
Subject: [PATCH] Update xsns_21_sgp30.ino

---
 sonoff/xsns_21_sgp30.ino | 105 +++++++++++++++++++++++++++++++--------
 1 file changed, 85 insertions(+), 20 deletions(-)

diff --git a/sonoff/xsns_21_sgp30.ino b/sonoff/xsns_21_sgp30.ino
index d8241f1d6..16c4657ad 100644
--- a/sonoff/xsns_21_sgp30.ino
+++ b/sonoff/xsns_21_sgp30.ino
@@ -34,65 +34,130 @@ Adafruit_SGP30 sgp;
 
 uint8_t sgp30_type = 0;
 uint8_t sgp30_ready = 0;
-uint8_t sgp30_counter = 0;
+float sgp30_abshum;
 
 /********************************************************************************************/
 
+void sgp30_Init(void) {
+  if (sgp.begin()) {
+    sgp30_type = 1;
+//      snprintf_P(log_data, sizeof(log_data), PSTR("SGP: Serialnumber 0x%04X-0x%04X-0x%04X"), sgp.serialnumber[0], sgp.serialnumber[1], sgp.serialnumber[2]);
+//      AddLog(LOG_LEVEL_DEBUG);
+    snprintf_P(log_data, sizeof(log_data), S_LOG_I2C_FOUND_AT, "SGP30", 0x58);
+    AddLog(LOG_LEVEL_DEBUG);
+  }
+}
+
+float sgp30_AbsoluteHumidity(float temperature, float humidity,char tempUnit) {
+  //taken from https://carnotcycle.wordpress.com/2012/08/04/how-to-convert-relative-humidity-to-absolute-humidity/
+  //precision is about 0.1°C in range -30 to 35°C
+  //August-Roche-Magnus 	6.1094 exp(17.625 x T)/(T + 243.04)
+  //Buck (1981) 		6.1121 exp(17.502 x T)/(T + 240.97)
+  //reference https://www.eas.ualberta.ca/jdwilson/EAS372_13/Vomel_CIRES_satvpformulae.html
+  float temp = NAN;
+  const float mw = 18.01534; 	// molar mass of water g/mol
+  const float r = 8.31447215; 	// Universal gas constant J/mol/K
+
+  if (isnan(temperature) || isnan(humidity) ) {
+    return NAN;
+  }
+
+  if (tempUnit != 'C') {
+        temperature = (temperature - 32.0) * (5.0 / 9.0); /*conversion to [°C]*/
+  }
+
+  temp = pow(2.718281828, (17.67 * temperature) / (temperature + 243.5));
+
+  //return (6.112 * temp * humidity * 2.1674) / (273.15 + temperature); 	//simplified version
+  return (6.112 * temp * humidity * mw) / ((273.15 + temperature) * r); 	//long version
+}
+
+#define SAVE_PERIOD 30
+
 void Sgp30Update(void)  // Perform every second to ensure proper operation of the baseline compensation algorithm
 {
   sgp30_ready = 0;
-  if (!sgp30_type) {
-    if (sgp.begin()) {
-      sgp30_type = 1;
-//      AddLog_P2(LOG_LEVEL_DEBUG, PSTR("SGP: Serialnumber 0x%04X-0x%04X-0x%04X"), sgp.serialnumber[0], sgp.serialnumber[1], sgp.serialnumber[2]);
-      AddLog_P2(LOG_LEVEL_DEBUG, S_LOG_I2C_FOUND_AT, "SGP30", 0x58);
+  if (!sgp.IAQmeasure() || !sgp30_type) {
+    // retry to init every 100 seconds
+    if (21 == (uptime %100)) {
+      sgp30_Init();
     }
-  } else {
-    if (!sgp.IAQmeasure()) return;  // Measurement failed
-    sgp30_counter++;
-    if (30 == sgp30_counter) {
-      sgp30_counter = 0;
+    return;  // Measurement failed
+  }
+  if (global_update) {
+    // abs hum in mg/m3
+    sgp30_abshum=sgp30_AbsoluteHumidity(global_temperature,global_humidity,TempUnit());
+    sgp.setHumidity(sgp30_abshum*1000);
+  }
+  sgp30_ready = 1;
 
-      uint16_t TVOC_base;
-      uint16_t eCO2_base;
+  // these should normally be stored permanently and used for fast restart
+  if (!(uptime%SAVE_PERIOD)) {
+    // store settings every N seconds
+    uint16_t TVOC_base;
+    uint16_t eCO2_base;
+
+    if (!sgp.getIAQBaseline(&eCO2_base, &TVOC_base)) return;  // Failed to get baseline readings
+//      snprintf_P(log_data, sizeof(log_data), PSTR("SGP: Baseline values eCO2 0x%04X, TVOC 0x%04X"), eCO2_base, TVOC_base);
+//      AddLog(LOG_LEVEL_DEBUG);
 
-      if (!sgp.getIAQBaseline(&eCO2_base, &TVOC_base)) return;  // Failed to get baseline readings
-//      AddLog_P2(LOG_LEVEL_DEBUG, PSTR("SGP: Baseline values eCO2 0x%04X, TVOC 0x%04X"), eCO2_base, TVOC_base);
-    }
-    sgp30_ready = 1;
   }
 }
 
+
+#ifdef USE_WEBSERVER
 const char HTTP_SNS_SGP30[] PROGMEM =
   "{s}SGP30 " D_ECO2 "{m}%d " D_UNIT_PARTS_PER_MILLION "{e}"                // {s} = <tr><th>, {m} = </th><td>, {e} = </td></tr>
   "{s}SGP30 " D_TVOC "{m}%d " D_UNIT_PARTS_PER_BILLION "{e}";
+const char HTTP_SNS_AHUM[] PROGMEM = "{s}SGP30 " "Abs Humidity" "{m}%s g/m3{e}";
+#endif
+
+#define D_JSON_AHUM "aHumidity"
 
 void Sgp30Show(bool json)
 {
   if (sgp30_ready) {
+    char abs_hum[33];
+
+    if (global_update) {
+      // has humidity + temperature
+      dtostrfd(sgp30_abshum,4,abs_hum);
+    }
+
     if (json) {
-      ResponseAppend_P(PSTR(",\"SGP30\":{\"" D_JSON_ECO2 "\":%d,\"" D_JSON_TVOC "\":%d}"), sgp.eCO2, sgp.TVOC);
+      ResponseAppend_P(PSTR(",\"SGP30\":{\"" D_JSON_ECO2 "\":%d,\"" D_JSON_TVOC "\":%d"), sgp.eCO2, sgp.TVOC);
+      if (global_update) {
+        ResponseAppend_P(PSTR(",\"" D_JSON_AHUM "\":%s"),abs_hum);
+      }
+      ResponseAppend_P(PSTR("}"));
 #ifdef USE_DOMOTICZ
       if (0 == tele_period) DomoticzSensor(DZ_AIRQUALITY, sgp.eCO2);
 #endif  // USE_DOMOTICZ
 #ifdef USE_WEBSERVER
     } else {
       WSContentSend_PD(HTTP_SNS_SGP30, sgp.eCO2, sgp.TVOC);
+      if (global_update) {
+        WSContentSend_PD(HTTP_SNS_AHUM, abs_hum);
+      }
 #endif
     }
   }
 }
 
+
 /*********************************************************************************************\
  * Interface
 \*********************************************************************************************/
 
-bool Xsns21(uint8_t function)
+bool Xsns21(byte function)
 {
   bool result = false;
 
   if (i2c_flg) {
     switch (function) {
+      case FUNC_INIT:
+        sgp30_Init();
+        break;
       case FUNC_EVERY_SECOND:
         Sgp30Update();
         break;
@@ -110,4 +175,4 @@ bool Xsns21(uint8_t function)
 }
 
 #endif  // USE_SGP30
-#endif  // USE_I2C
\ No newline at end of file
+#endif  // USE_I2C