Fork of the espurna firmware for `mhsw` switches
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// -----------------------------------------------------------------------------
// SI7021 / HTU21D Sensor over I2C
// Copyright (C) 2017-2018 by Xose Pérez <xose dot perez at gmail dot com>
// -----------------------------------------------------------------------------
#if SENSOR_SUPPORT && SI7021_SUPPORT
#pragma once
#include "Arduino.h"
#include "I2CSensor.h"
#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
PROGMEM const char si7021_chip_si7021_name[] = "SI7021";
PROGMEM const char si7021_chip_htu21d_name[] = "HTU21D";
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;
// Initialize sensor
_init();
}
// Descriptive name of the sensor
String description() {
char name[10];
strncpy_P(name,
_chip == SI7021_CHIP_SI7021 ?
si7021_chip_si7021_name :
si7021_chip_htu21d_name,
sizeof(name)
);
char buffer[25];
snprintf(buffer, sizeof(buffer), "%s @ I2C (0x%02X)", name, _address);
return String(buffer);
}
// Descriptive name of the slot # index
String slot(unsigned char index) {
return description();
};
// Type for slot # index
unsigned char type(unsigned char index) {
if (index == 0) return MAGNITUDE_TEMPERATURE;
if (index == 1) return MAGNITUDE_HUMIDITY;
return MAGNITUDE_NONE;
}
// Pre-read hook (usually to populate registers with up-to-date data)
void pre() {
_error = SENSOR_ERROR_UNKNOWN_ID;
if (_chip == 0) return;
_error = SENSOR_ERROR_OK;
double value;
value = _read(SI7021_CMD_TMP_NOHOLD);
if (_error != SENSOR_ERROR_OK) return;
_temperature = (175.72 * value / 65536) - 46.85;
value = _read(SI7021_CMD_HUM_NOHOLD);
if (_error != SENSOR_ERROR_OK) return;
value = (125.0 * value / 65536) - 6;
_humidity = constrain(value, 0, 100);
}
// Current value for slot # index
double value(unsigned char index) {
if (index == 0) return _temperature;
if (index == 1) return _humidity;
return 0;
}
protected:
// ---------------------------------------------------------------------
// Protected
// ---------------------------------------------------------------------
void _init() {
// Check device
i2c_write_uint8(_address, 0xFC, 0xC9);
_chip = i2c_read_uint8(_address);
if ((_chip != SI7021_CHIP_SI7021) & (_chip != SI7021_CHIP_HTU21D)) {
i2cReleaseLock(_address);
_error = SENSOR_ERROR_UNKNOWN_ID;
_count = 0;
} else {
_count = 2;
}
}
unsigned int _read(uint8_t command) {
// Request measurement
i2c_write_uint8(_address, command);
// 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);
// Clear the last to bits of LSB to 00.
// According to datasheet LSB of RH is always xxxxxx10
unsigned int value = i2c_read_uint16(_address) & 0xFFFC;
// We should be checking there are no pending bytes in the buffer
// and raise a CRC error if there are
_error = SENSOR_ERROR_OK;
return value;
}
unsigned char _chip;
double _temperature = 0;
double _humidity = 0;
};
#endif // SENSOR_SUPPORT && SI7021_SUPPORT