7a25e14a8f
* Newline in log isn't nice. * I managed to confuse even myself with this 0x4a. It's actually not used anywhere currently.
129 lines
3.1 KiB
C++
129 lines
3.1 KiB
C++
/*
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* SensorTempSHT20.cpp
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*
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* Created on: 16 May 2023
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*/
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#include "SensorTempSHT20.h"
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#include "FreeRTOS.h"
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#include "task.h"
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#include "Log.h"
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//D6U9H:
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//D - Digital (i2c)
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//6 - 2016 year of production
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//U9H - Sensirion undecodable crap
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//Address: 0x40
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//Trigger T measurement | hold master | 1110 0011 - 0xe3 (implemented)
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//Trigger T measurement | no hold master | 1111 0011 - 0xf3
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//Write user register | | 1110 0110 - 0xe6
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//Read user register | | 1110 0111 - 0xe7
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//Soft reset | | 1111 1110 - 0xfe
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SensorTempSHT20::SensorTempSHT20(I2C* pi2c)
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: _pi2c(pi2c), _dev_addr(0x40), _up_flag(false),
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_com_read_hold(0xe3), _com_read_nohold(0xf3),
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_com_write_ur(0xe6), _com_read_ur(0xe7),
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_com_soft_reset(0xfe), _polynominal(0x131)
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{
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//Read sensor during the initialisation to get the "UP" state earlier.
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this->read();
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}
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SensorTempSHT20::~SensorTempSHT20()
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{}
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/**
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* @brief Gets temperature from SHT20 sensor.
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*
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* @return int8_t temperature value trimmed from -128 to 127.
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*/
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int8_t SensorTempSHT20::getTemperature()
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{
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uint16_t raw_temp = this->read();
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bool err_bit = raw_temp & 0x1;
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int temp = 0;
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if (err_bit)
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return -128;
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//Formula: (St / 2 ^ 16) * 175.72 - 46.85
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temp = ((double)raw_temp / 65536) * 175.72 - 46.85;
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if(temp > 127)
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temp = 127;
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if (temp < -128)
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temp = -128;
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return temp;
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}
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/**
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* @brief Makes sure that the sensor is up.
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*
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* @return true It is.
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* @return false It is not.
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*/
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bool SensorTempSHT20::is_up()
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{
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this->read();
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return this->_up_flag;
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}
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//Use hold master - read(com = 0xe3)
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//Reading is done via 3 bytes.
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//WRITE: I2C address + write | read command
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//READ: Data (MSB) | Data (LSB) + Stat. | Checksum
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/**
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* @brief Gets raw temperature measurement data from sensor
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* using hold master mode.
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*
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* @return uint16_t Raw temperature measurement data.
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*/
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uint16_t SensorTempSHT20::read()
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{
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uint8_t tbuf = this->_com_read_hold;
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uint8_t rbuf[3] = {0x0, 0x2, 0x0};
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uint8_t crc = 0x0;
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uint16_t raw_temp = 0;
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this->_up_flag = this->_pi2c->transaction(this->_dev_addr, &tbuf, 1, rbuf, 3);
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//Sensor changes this bit to 0 on temp measurement.
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if (rbuf[1] & 0x2)
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return 0x1;
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raw_temp |= (rbuf[0] << 8);
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raw_temp |= (rbuf[1] & 0xfc);
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crc = rbuf[2];
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if (this->crc_check(rbuf, 2, crc))
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LOG_WARNING("Temperature sensor reported crc mismatch. Raw data: %04x; CRC: %x", raw_temp, crc);
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return raw_temp;
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}
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/**
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* @brief Checks if checksum is correct.
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*
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* @param data array of raw data to check.
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* @param nbrOfBytes size of an array.
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* @param checksum received checksum to compare calculated crc to.
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* @return true - checksum is incorrect.
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* @return false - checksum is the same as calculated.
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*/
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bool SensorTempSHT20::crc_check(uint8_t * data, uint8_t nbrOfBytes, uint8_t checksum)
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{
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uint8_t crc = 0;
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uint8_t bit;
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uint8_t byteCtr;
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//Calculates 8-Bit checksum with given _polynomial
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for (byteCtr = 0; byteCtr < nbrOfBytes; ++byteCtr)
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{
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crc ^= (data[byteCtr]);
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for ( bit = 8; bit > 0; --bit)
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crc = (crc & 0x80) ? ((crc << 1) ^ this->_polynominal) : (crc << 1);
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}
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return crc != checksum;
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}
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