2022-08-25 20:51:51 +01:00
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/*
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xsns_98_sgp40.ino - SGP40 gas and air quality sensor support for Tasmota
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2022-12-10 15:55:04 +00:00
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Copyright (C) 2022 Jean-Pierre Deschamps
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2022-08-25 20:51:51 +01:00
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#ifdef USE_I2C
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#ifdef USE_SGP40
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/*********************************************************************************************\
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* SGP40 - Gas (TVOC - Total Volatile Organic Compounds) and Air Quality (CO2)
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*
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* Source: Gerhard Mutz and Adafruit Industries
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* Adaption for TASMOTA: Jean-Pierre Deschamps
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*
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* I2C Address: 0x59
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\*********************************************************************************************/
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#define XSNS_98 98
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#define XI2C_69 69 // See I2CDEVICES.md
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#define SGP40_ADDRESS 0x59
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#include "Adafruit_SGP40.h"
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Adafruit_SGP40 sgp40;
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bool sgp40_type = false;
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bool sgp40_ready = false;
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float sgp40_abshum;
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uint16_t raw_base;
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int32_t voc_index;
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/********************************************************************************************/
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void sgp40_Init(void)
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{
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if (!I2cSetDevice(SGP40_ADDRESS)) { return; }
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if (sgp40.begin()) {
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sgp40_type = true;
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// AddLog(LOG_LEVEL_DEBUG, PSTR("SGP: Serialnumber 0x%04X-0x%04X-0x%04X"), sgp40.serialnumber[0], sgp40.serialnumber[1], sgp40.serialnumber[2]);
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I2cSetActiveFound(SGP40_ADDRESS, "SGP40");
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}
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}
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//#define POW_FUNC pow
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#define POW_FUNC FastPrecisePow
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float sgp40_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/
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//precision is about 0.1°C in range -30 to 35°C
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//August-Roche-Magnus 6.1094 exp(17.625 x T)/(T + 243.04)
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//Buck (1981) 6.1121 exp(17.502 x T)/(T + 240.97)
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//reference https://www.eas.ualberta.ca/jdwilson/EAS372_13/Vomel_CIRES_satvpformulae.html
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float temp = NAN;
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const float mw = 18.01534f; // molar mass of water g/mol
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const float r = 8.31447215f; // Universal gas constant J/mol/K
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if (isnan(temperature) || isnan(humidity) ) {
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return NAN;
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}
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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
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return (6.112f * temp * humidity * mw) / ((273.15f + temperature) * r); //long version
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}
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#define SAVE_PERIOD 30
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void Sgp40Update(void) // Perform every second to ensure proper operation of the baseline compensation algorithm
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{
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sgp40_ready = false;
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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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sgp40_abshum = sgp40_AbsoluteHumidity(TasmotaGlobal.temperature_celsius, TasmotaGlobal.humidity);
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}
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sgp40_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
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raw_base = sgp40.measureRaw(TasmotaGlobal.temperature_celsius, TasmotaGlobal.humidity);
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voc_index = sgp40.measureVocIndex(TasmotaGlobal.temperature_celsius, TasmotaGlobal.humidity);
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}
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}
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#ifdef USE_WEBSERVER
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const char HTTP_SNS_SGP40[] PROGMEM =
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"{s}SGP40 " D_JSON_RAW "{m}%d " "{e}" // {s} = <tr><th>, {m} = </th><td>, {e} = </td></tr>
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"{s}SGP40 " D_AIR_QUALITY "{m}%d " "{e}";
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const char HTTP_SNS_AHUM40[] PROGMEM = "{s}SGP40 Abs Humidity{m}%s g/m3{e}";
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#endif
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void Sgp40Show(bool json)
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{
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if (sgp40_ready) {
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char abs_hum[33];
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bool ahum_available = TasmotaGlobal.global_update && (TasmotaGlobal.humidity > 0) && !isnan(TasmotaGlobal.temperature_celsius);
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if (ahum_available) {
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// has humidity + temperature
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dtostrfd(sgp40_abshum,4,abs_hum);
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}
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if (json) {
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ResponseAppend_P(PSTR(",\"SGP40\":{\"" D_JSON_RAW "\":%d,\"" D_JSON_AIRQUALITY "\":%d"), raw_base, voc_index);
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if (ahum_available) {
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ResponseAppend_P(PSTR(",\"" D_JSON_AHUM "\":%s"),abs_hum);
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}
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ResponseJsonEnd();
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#ifdef USE_DOMOTICZ
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2024-04-11 14:35:00 +01:00
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if (0 == TasmotaGlobal.tele_period) {
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DomoticzSensor(DZ_AIRQUALITY, voc_index);
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}
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2022-08-25 20:51:51 +01:00
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#endif // USE_DOMOTICZ
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#ifdef USE_WEBSERVER
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} else {
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WSContentSend_PD(HTTP_SNS_SGP40, raw_base, voc_index);
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if (ahum_available) {
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WSContentSend_PD(HTTP_SNS_AHUM40, abs_hum);
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}
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#endif
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}
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}
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}
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/*********************************************************************************************\
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* Interface
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\*********************************************************************************************/
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2022-11-11 09:44:56 +00:00
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bool Xsns98(uint32_t function)
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2022-08-25 20:51:51 +01:00
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{
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if (!I2cEnabled(XI2C_69)) { return false; }
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bool result = false;
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if (FUNC_INIT == function) {
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sgp40_Init();
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}
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else if (sgp40_type) {
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switch (function) {
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case FUNC_EVERY_SECOND:
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Sgp40Update();
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break;
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case FUNC_JSON_APPEND:
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Sgp40Show(1);
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break;
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#ifdef USE_WEBSERVER
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case FUNC_WEB_SENSOR:
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Sgp40Show(0);
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break;
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#endif // USE_WEBSERVER
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}
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}
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return result;
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}
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#endif // USE_SGP40
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#endif // USE_I2C
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