Tasmota/tasmota/xsns_21_sgp30.ino

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/*
xsns_21_sgp30.ino - SGP30 gas and air quality sensor support for Tasmota
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Copyright (C) 2021 Theo Arends
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#ifdef USE_I2C
#ifdef USE_SGP30
/*********************************************************************************************\
* SGP30 - Gas (TVOC - Total Volatile Organic Compounds) and Air Quality (CO2)
*
* Source: Gerhard Mutz and Adafruit Industries
*
* I2C Address: 0x58
\*********************************************************************************************/
#define XSNS_21 21
#define XI2C_18 18 // See I2CDEVICES.md
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#define SGP30_ADDRESS 0x58
#include "Adafruit_SGP30.h"
Adafruit_SGP30 sgp;
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bool sgp30_type = false;
bool sgp30_ready = false;
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float sgp30_abshum;
/********************************************************************************************/
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void sgp30_Init(void)
{
if (!I2cSetDevice(SGP30_ADDRESS)) { return; }
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if (sgp.begin()) {
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sgp30_type = true;
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// AddLog(LOG_LEVEL_DEBUG, PSTR("SGP: Serialnumber 0x%04X-0x%04X-0x%04X"), sgp.serialnumber[0], sgp.serialnumber[1], sgp.serialnumber[2]);
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I2cSetActiveFound(SGP30_ADDRESS, "SGP30");
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}
}
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//#define POW_FUNC pow
#define POW_FUNC FastPrecisePow
float sgp30_AbsoluteHumidity(float temperature, float humidity) {
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//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 = 18.01534f; // molar mass of water g/mol
const float r = 8.31447215f; // Universal gas constant J/mol/K
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if (isnan(temperature) || isnan(humidity) ) {
return NAN;
}
temp = POW_FUNC(2.718281828f, (17.67f * temperature) / (temperature + 243.5f));
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//return (6.112 * temp * humidity * 2.1674) / (273.15 + temperature); //simplified version
return (6.112f * temp * humidity * mw) / ((273.15f + temperature) * r); //long version
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}
#define SAVE_PERIOD 30
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void Sgp30Update(void) // Perform every second to ensure proper operation of the baseline compensation algorithm
{
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sgp30_ready = false;
if (!sgp.IAQmeasure()) {
return; // Measurement failed
}
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if (TasmotaGlobal.global_update && (TasmotaGlobal.humidity > 0) && !isnan(TasmotaGlobal.temperature_celsius)) {
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// abs hum in mg/m3
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sgp30_abshum = sgp30_AbsoluteHumidity(TasmotaGlobal.temperature_celsius, TasmotaGlobal.humidity);
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sgp.setHumidity(sgp30_abshum*1000);
}
sgp30_ready = true;
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// these should normally be stored permanently and used for fast restart
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if (!(TasmotaGlobal.uptime%SAVE_PERIOD)) {
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// store settings every N seconds
uint16_t TVOC_base;
uint16_t eCO2_base;
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if (!sgp.getIAQBaseline(&eCO2_base, &TVOC_base)) return; // Failed to get baseline readings
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// AddLog(LOG_LEVEL_DEBUG, PSTR("SGP: Baseline values eCO2 0x%04X, TVOC 0x%04X"), eCO2_base, TVOC_base);
}
}
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#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}";
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const char HTTP_SNS_AHUM[] PROGMEM = "{s}SGP30 Abs Humidity{m}%s g/m3{e}";
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#endif
#define D_JSON_AHUM "aHumidity"
void Sgp30Show(bool json)
{
if (sgp30_ready) {
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char abs_hum[33];
bool ahum_available = TasmotaGlobal.global_update && (TasmotaGlobal.humidity > 0) && !isnan(TasmotaGlobal.temperature_celsius);
if (ahum_available) {
// has humidity + temperature
dtostrfd(sgp30_abshum,4,abs_hum);
}
if (json) {
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ResponseAppend_P(PSTR(",\"SGP30\":{\"" D_JSON_ECO2 "\":%d,\"" D_JSON_TVOC "\":%d"), sgp.eCO2, sgp.TVOC);
if (ahum_available) {
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ResponseAppend_P(PSTR(",\"" D_JSON_AHUM "\":%s"),abs_hum);
}
ResponseJsonEnd();
#ifdef USE_DOMOTICZ
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if (0 == TasmotaGlobal.tele_period) DomoticzSensor(DZ_AIRQUALITY, sgp.eCO2);
#endif // USE_DOMOTICZ
#ifdef USE_WEBSERVER
} else {
WSContentSend_PD(HTTP_SNS_SGP30, sgp.eCO2, sgp.TVOC);
if (ahum_available) {
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WSContentSend_PD(HTTP_SNS_AHUM, abs_hum);
}
#endif
}
}
}
/*********************************************************************************************\
* Interface
\*********************************************************************************************/
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bool Xsns21(uint8_t function)
{
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if (!I2cEnabled(XI2C_18)) { return false; }
bool result = false;
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if (FUNC_INIT == function) {
sgp30_Init();
}
else if (sgp30_type) {
switch (function) {
case FUNC_EVERY_SECOND:
Sgp30Update();
break;
case FUNC_JSON_APPEND:
Sgp30Show(1);
break;
#ifdef USE_WEBSERVER
case FUNC_WEB_SENSOR:
Sgp30Show(0);
break;
#endif // USE_WEBSERVER
}
}
return result;
}
#endif // USE_SGP30
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#endif // USE_I2C