Canberk Sönmez
/
SHT21
A simple example adopting SHT21 Arduino library to mbed.
Diff: main.cpp
- Revision:
- 1:f4a1942b4486
- Parent:
- 0:062188c0bb61
--- a/main.cpp Thu Aug 10 13:25:37 2017 +0000 +++ b/main.cpp Wed Sep 13 13:36:04 2017 +0000 @@ -1,143 +1,5 @@ #include "mbed.h" - -/** - * A simple library for SHT21 humidity and temperature sensor. - * Based on the Arduino library. - */ - -class SHT21 { -public: - SHT21(PinName sda, PinName scl, char addr = (0x40 << 1)); - SHT21(I2C &i2c, char addr = (0x40 << 1)); - - float temperature(); - float humidity(); - - void reset(); - void serialNumber(uint8_t *serialNumber); - - ~SHT21(); -private: - enum commands { - TRIGGER_T_MEASUREMENT_HM = 0xE3, - TRIGGER_RH_MEASUREMENT_HM = 0xE5, - TRIGGER_T_MEASUREMENT_NHM = 0xF3, - TRIGGER_RH_MEASUREMENT_NHM = 0xF5, - USER_REGISTER_W = 0xE6, - USER_REGISTER_R = 0xE7, - SOFT_RESET = 0xFE - }; - - static const uint16_t POLYNOMIAL; - - char addr_; - I2C *pi2c_; - I2C &i2c_; - - uint16_t readRaw(uint8_t cmd); - static bool crcChecksum(const uint8_t *data, uint8_t sz, uint8_t checksum); -}; - -const uint16_t SHT21::POLYNOMIAL = 0x131; - -SHT21::SHT21(PinName sda, PinName scl, char addr) : - addr_(addr), - pi2c_(new I2C(sda, scl)), - i2c_(*pi2c_) { -} - -SHT21::SHT21(I2C &i2c, char addr) : - addr_(addr), - pi2c_(NULL), - i2c_(i2c) { -} - -float SHT21::temperature() { - uint16_t r = readRaw(TRIGGER_T_MEASUREMENT_HM); - r &= ~0x0003; - return (-46.85 + 175.72/65536 * (float) r); -} - -float SHT21::humidity() { - uint16_t r = readRaw(TRIGGER_RH_MEASUREMENT_HM); - r &= ~0x0003; - return (-6.0 + 125.0/65536 * (float) r); -} - -void SHT21::reset() { - uint8_t pcmd [] = { SOFT_RESET }; - i2c_.write(addr_, (const char *) pcmd, 1); - wait_ms(15); -} - -void SHT21::serialNumber(uint8_t *serialNumber) { - uint8_t data[8]; - uint8_t pcmd0[2] = { 0xFA, 0x0F }; - uint8_t pcmd1[2] = { 0xFC, 0xC9 }; - uint8_t i = 0; - i2c_.write(addr_, (const char *) pcmd0, 2); - i2c_.read(addr_, (char *) data, 8); - - serialNumber[5] = data[i++]; - i++; - serialNumber[4] = data[i++]; - i++; - serialNumber[3] = data[i++]; - i++; - serialNumber[2] = data[i++]; - i = 0; - - i2c_.write(addr_, (const char *) pcmd1, 2); - i2c_.read(addr_, (char *) data, 6); - - serialNumber[1] = data[i++]; - serialNumber[0] = data[i++]; - i++; - serialNumber[7] = data[i++]; - serialNumber[8] = data[i++]; - i = 0; -} - -SHT21::~SHT21() { - if (pi2c_) delete pi2c_; -} - -uint16_t SHT21::readRaw(uint8_t cmd) { - uint8_t checksum; - uint8_t data[2]; - uint16_t result; - - uint8_t pcmd [] = { cmd }; - - i2c_.write(addr_, (const char *) pcmd, 1); - i2c_.read(addr_, (char *) data, 2); - i2c_.read(addr_, (char *) &checksum, 1); - - result = data[0] << 8; - result += data[1]; - - if (crcChecksum(data, 2, checksum)) { - reset(); - return 1; - } - return result; -} - -bool SHT21::crcChecksum(const uint8_t *data, uint8_t sz, uint8_t checksum) { - uint8_t crc = 0; - - for (uint8_t i = 0; i < sz; ++i) { - crc ^= data[i]; - for (uint8_t j /* bit index */ = 8; j > 0; --j) { - if (crc & 0x80) - crc = (crc << 1) ^ POLYNOMIAL; - else - crc = (crc << 1); - } - } - - return crc == checksum; -} +#include "SHT21.hpp" SHT21 sht21(PB_9 /* I2C_SDA */, PB_8 /* I2C_SCL */); Serial pc(USBTX, USBRX);