Fork of the espurna firmware for `mhsw` switches
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// -----------------------------------------------------------------------------
// SI7021 / HTU21D Sensor over I2C
// Copyright (C) 2017 by Xose Pérez <xose dot perez at gmail dot com>
// -----------------------------------------------------------------------------
#if SENSOR_SUPPORT && SI7021_SUPPORT
#pragma once
#include "Arduino.h"
#include "I2CSensor.h"
#if I2C_USE_BRZO
#include <brzo_i2c.h>
#else
#include <Wire.h>
#endif
#define SI7021_SCL_FREQUENCY 200
#define SI7021_CHIP_SI7021 0x15
#define SI7021_CHIP_HTU21D 0x32
#define SI7021_CMD_TMP_HOLD 0xE3
#define SI7021_CMD_HUM_HOLD 0xE5
#define SI7021_CMD_TMP_NOHOLD 0xF3
#define SI7021_CMD_HUM_NOHOLD 0xF5
class SI7021Sensor : public I2CSensor {
public:
// ---------------------------------------------------------------------
// Public
// ---------------------------------------------------------------------
SI7021Sensor(): I2CSensor() {
_sensor_id = SENSOR_SI7021_ID;
}
// ---------------------------------------------------------------------
// Sensor API
// ---------------------------------------------------------------------
// Initialization method, must be idempotent
void begin() {
if (!_dirty) return;
_dirty = false;
// I2C auto-discover
unsigned char addresses[] = {0x40};
_address = _begin_i2c(_address, sizeof(addresses), addresses);
if (_address == 0) return;
// Check device
#if I2C_USE_BRZO
uint8_t buffer[2] = {0xFC, 0xC9};
brzo_i2c_start_transaction(_address, SI7021_SCL_FREQUENCY);
brzo_i2c_write(buffer, 2, false);
brzo_i2c_read(buffer, 1, false);
brzo_i2c_end_transaction();
_chip = buffer[0];
#else
Wire.beginTransmission(_address);
Wire.write(0xFC);
Wire.write(0xC9);
Wire.endTransmission();
Wire.requestFrom(_address, (unsigned char) 1);
_chip = Wire.read();
#endif
if ((_chip != SI7021_CHIP_SI7021) & (_chip != SI7021_CHIP_HTU21D)) {
i2cReleaseLock(_address);
_error = SENSOR_ERROR_UNKNOWN_ID;
} else {
_count = 2;
}
}
// Descriptive name of the sensor
String description() {
char buffer[25];
snprintf(buffer, sizeof(buffer), "%s @ I2C (0x%02X)", chipAsString().c_str(), _address);
return String(buffer);
}
// Type for slot # index
unsigned char type(unsigned char index) {
if (index < _count) {
_error = SENSOR_ERROR_OK;
if (index == 0) return MAGNITUDE_TEMPERATURE;
if (index == 1) return MAGNITUDE_HUMIDITY;
}
_error = SENSOR_ERROR_OUT_OF_RANGE;
return MAGNITUDE_NONE;
}
// Current value for slot # index
double value(unsigned char index) {
if (index < _count) {
_error = SENSOR_ERROR_OK;
double value;
if (index == 0) {
value = read(SI7021_CMD_TMP_NOHOLD);
value = (175.72 * value / 65536) - 46.85;
}
if (index == 1) {
value = read(SI7021_CMD_HUM_NOHOLD);
value = (125.0 * value / 65536) - 6;
value = constrain(value, 0, 100);
}
return value;
}
_error = SENSOR_ERROR_OUT_OF_RANGE;
return 0;
}
protected:
// ---------------------------------------------------------------------
// Protected
// ---------------------------------------------------------------------
unsigned int read(uint8_t command) {
unsigned char bytes = (command == 0xE0) ? 2 : 3;
#if I2C_USE_BRZO
uint8_t buffer[2] = {command, 0x00};
brzo_i2c_start_transaction(_address, SI7021_SCL_FREQUENCY);
brzo_i2c_write(buffer, 1, false);
#else
Wire.beginTransmission(_address);
Wire.write(command);
Wire.endTransmission();
#endif
// When not using clock stretching (*_NOHOLD commands) delay here
// is needed to wait for the measurement.
// According to datasheet the max. conversion time is ~22ms
unsigned long start = millis();
while (millis() - start < 50) delay(1);
#if I2C_USE_BRZO
brzo_i2c_read(buffer, 2, false);
brzo_i2c_end_transaction();
unsigned int msb = buffer[0];
unsigned int lsb = buffer[1];
#else
Wire.requestFrom(_address, bytes);
if (Wire.available() != bytes) {
_error = SENSOR_ERROR_CRC;
return 0;
}
unsigned int msb = Wire.read();
unsigned int lsb = Wire.read();
#endif
// Clear the last to bits of LSB to 00.
// According to datasheet LSB of RH is always xxxxxx10
lsb &= 0xFC;
unsigned int value = (msb << 8) | lsb;
_error = SENSOR_ERROR_OK;
return value;
}
String chipAsString() {
if (_chip == SI7021_CHIP_SI7021) return String("SI7021");
if (_chip == SI7021_CHIP_HTU21D) return String("HTU21D");
return String("Unknown");
}
unsigned char _chip;
};
#endif // SENSOR_SUPPORT && SI7021_SUPPORT