mirror of https://github.com/arendst/Tasmota.git
221 lines
7.9 KiB
C++
221 lines
7.9 KiB
C++
/*
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xsns_39_max31855.ino - MAX31855 thermocouple sensor support for Tasmota
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Copyright (C) 2021 Markus Past
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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_MAX31855
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/*********************************************************************************************\
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* MAX31855 and MAX6675 - Thermocouple
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*
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* SetOption94 0 - MAX31855
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* SetOption94 1 - MAX6675
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\*********************************************************************************************/
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#define XSNS_39 39
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const char kMax31855Types[] PROGMEM = "MAX31855|MAX6675";
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bool max31855_initialized = false;
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uint8_t max31855_pins_used = 0; //used as a bit array
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uint8_t max31855_count = 0;
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struct MAX31855_ResultStruct {
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uint8_t ErrorCode; // Error Codes: 0 = No Error / 1 = TC open circuit / 2 = TC short to GND / 4 = TC short to VCC
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float ProbeTemperature; // Measured temperature of the 'hot' TC junction (probe temp)
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float ReferenceTemperature; // Measured temperature of the 'cold' TC junction (reference temp)
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} MAX31855_Result[MAX_MAX31855S];
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void MAX31855_Init(void) {
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if (PinUsed(GPIO_MAX31855CLK) && PinUsed(GPIO_MAX31855DO)) {
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// Set GPIO modes for SW-SPI
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pinMode(Pin(GPIO_MAX31855CLK), OUTPUT);
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pinMode(Pin(GPIO_MAX31855DO), INPUT);
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// Clock low
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digitalWrite(Pin(GPIO_MAX31855CLK), LOW);
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for (uint32_t i = 0; i < MAX_MAX31855S; i++) {
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if (PinUsed(GPIO_MAX31855CS, i)) {
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max31855_pins_used |= 1 << i; //set lowest bit
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max31855_count ++;
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// Set GPIO modes for SW-SPI
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pinMode(Pin(GPIO_MAX31855CS, i), OUTPUT);
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// Chip not selected
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digitalWrite(Pin(GPIO_MAX31855CS, i), HIGH);
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max31855_initialized = true;
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}
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}
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}
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}
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/*
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* MAX31855_ShiftIn(uint8_t Length, uint32_t index)
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* Communicates with MAX31855 via SW-SPI and returns the raw data read from the chip
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*/
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int32_t MAX31855_ShiftIn(uint8_t Length, uint32_t index) {
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int32_t dataIn = 0;
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digitalWrite(Pin(GPIO_MAX31855CS, index), LOW); // CS = LOW -> Start SPI communication
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delayMicroseconds(1); // CS fall to output enable = max. 100ns
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for (uint32_t i = 0; i < Length; i++) {
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digitalWrite(Pin(GPIO_MAX31855CLK), LOW);
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delayMicroseconds(1); // CLK pulse width low = min. 100ns / CLK fall to output valid = max. 40ns
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dataIn <<= 1;
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if (digitalRead(Pin(GPIO_MAX31855DO))) {
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dataIn |= 1;
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}
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digitalWrite(Pin(GPIO_MAX31855CLK), HIGH);
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delayMicroseconds(1); // CLK pulse width high = min. 100ns
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}
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digitalWrite(Pin(GPIO_MAX31855CS, index), HIGH); // CS = HIGH -> End SPI communication
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digitalWrite(Pin(GPIO_MAX31855CLK), LOW);
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return dataIn;
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}
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/*
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* MAX31855_GetProbeTemperature(int32_t RawData)
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* Decodes and returns the temperature of TCs 'hot' junction from RawData
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*/
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float MAX31855_GetProbeTemperature(int32_t RawData) {
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if (RawData & 0x80000000) {
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RawData = (RawData >> 18) | 0xFFFFC000; // Negative value - Drop lower 18 bits and extend to negative number
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} else {
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RawData >>= 18; // Positiv value - Drop lower 18 bits
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}
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float result = (RawData * 0.25f); // MAX31855 LSB resolution is 0.25°C for probe temperature
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return ConvertTemp(result); // Check if we have to convert to Fahrenheit
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}
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/*
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* MAX31855_GetReferenceTemperature(int32_t RawData)
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* Decodes and returns the temperature of TCs 'cold' junction from RawData
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*/
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float MAX31855_GetReferenceTemperature(int32_t RawData) {
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if (RawData & 0x8000) {
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RawData = (RawData >> 4) | 0xFFFFF000; // Negative value - Drop lower 4 bits and extend to negative number
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} else {
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RawData = (RawData >> 4) & 0x00000FFF; // Positiv value - Drop lower 4 bits and mask out remaining bits (probe temp, error bit, etc.)
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}
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float result = (RawData * 0.0625f); // MAX31855 LSB resolution is 0.0625°C for reference temperature
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return ConvertTemp(result); // Check if we have to convert to Fahrenheit
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}
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/*
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* MAX31855_GetResult(void)
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* Acquires the raw data via SPI, checks for MAX31855 errors and fills result structure
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*/
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void MAX31855_GetResult(void) {
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for (uint32_t i = 0; i < MAX_MAX31855S; i++) {
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if (max31855_pins_used & (1 << i)) {
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if (Settings->flag4.max6675) { // SetOption94 - Implement simpler MAX6675 protocol instead of MAX31855
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int32_t RawData = MAX31855_ShiftIn(16, i);
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int32_t temp = (RawData >> 3) & ((1 << 12) - 1);
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/* Occasionally the sensor returns 0xfff, consider it an error */
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if (temp == ((1 << 12) - 1)) { return; }
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MAX31855_Result[i].ErrorCode = 0;
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MAX31855_Result[i].ReferenceTemperature = NAN;
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MAX31855_Result[i].ProbeTemperature = ConvertTemp(0.25f * temp);
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} else {
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int32_t RawData = MAX31855_ShiftIn(32, i);
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uint8_t probeerror = RawData & 0x7;
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MAX31855_Result[i].ErrorCode = probeerror;
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MAX31855_Result[i].ReferenceTemperature = MAX31855_GetReferenceTemperature(RawData);
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if (probeerror) {
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MAX31855_Result[i].ProbeTemperature = NAN; // Return NaN if MAX31855 reports an error
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} else {
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MAX31855_Result[i].ProbeTemperature = MAX31855_GetProbeTemperature(RawData);
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}
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}
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}
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}
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}
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void MAX31855_Show(bool Json) {
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char sensor_name_text[10];
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char sensor_name[12];
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uint8_t report_once = 0;
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GetTextIndexed(sensor_name_text, sizeof(sensor_name_text), Settings->flag4.max6675, kMax31855Types);
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sprintf(sensor_name, "%s",sensor_name_text);
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for (uint32_t i = 0; i < MAX_MAX31855S; i++) {
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if (max31855_pins_used & (1 << i)) {
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if (max31855_count > 1) {
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sprintf(sensor_name, "%s%c%d",sensor_name_text, IndexSeparator(), i);
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}
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if (Json) {
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ResponseAppend_P(PSTR(",\"%s\":{\"" D_JSON_TEMPERATURE "\":%*_f,\"" D_JSON_REFERENCETEMPERATURE "\":%*_f,\"" D_JSON_ERROR "\":%d}"), \
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sensor_name,
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Settings->flag2.temperature_resolution, &MAX31855_Result[i].ProbeTemperature,
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Settings->flag2.temperature_resolution, &MAX31855_Result[i].ReferenceTemperature,
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MAX31855_Result[i].ErrorCode);
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if ((0 == TasmotaGlobal.tele_period) && (!report_once)) {
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#ifdef USE_DOMOTICZ
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DomoticzFloatSensor(DZ_TEMP, MAX31855_Result[i].ProbeTemperature);
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#endif // USE_DOMOTICZ
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#ifdef USE_KNX
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KnxSensor(KNX_TEMPERATURE, MAX31855_Result[i].ProbeTemperature);
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#endif // USE_KNX
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report_once++;
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}
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#ifdef USE_WEBSERVER
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} else {
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WSContentSend_Temp(sensor_name, MAX31855_Result[i].ProbeTemperature);
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#endif // USE_WEBSERVER
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}
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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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bool Xsns39(uint32_t function)
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{
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bool result = false;
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if (FUNC_INIT == function) {
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MAX31855_Init();
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}
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else if (max31855_initialized) {
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switch (function) {
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case FUNC_EVERY_SECOND:
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MAX31855_GetResult();
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break;
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case FUNC_JSON_APPEND:
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MAX31855_Show(true);
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break;
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#ifdef USE_WEBSERVER
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case FUNC_WEB_SENSOR:
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MAX31855_Show(false);
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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_MAX31855
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