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- // -----------------------------------------------------------------------------
- // SI7021 / HTU21D Sensor over I2C
- // Copyright (C) 2017 by Xose Pérez <xose dot perez at gmail dot com>
- // -----------------------------------------------------------------------------
-
- #pragma once
-
- #include "Arduino.h"
- #include "BaseSensor.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 BaseSensor {
-
- public:
-
- // ---------------------------------------------------------------------
- // Public
- // ---------------------------------------------------------------------
-
- void setAddress(unsigned char address) {
- if (_address != address) _dirty = true;
- _address = address;
- }
-
- // ---------------------------------------------------------------------
-
- unsigned char getAddress() {
- return _address;
- }
-
- // ---------------------------------------------------------------------
- // Sensor API
- // ---------------------------------------------------------------------
-
- // Initialization method, must be idempotent
- void begin() {
-
- if (!_dirty) return;
- _dirty = false;
-
- // I2C auto-discover
- unsigned char addresses[] = {0x40};
- _address = lock_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);
- }
-
- // Descriptive name of the slot # index
- String slot(unsigned char index) {
- return description();
- }
-
- // Type for slot # index
- magnitude_t 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;
-
- };
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