Adafruit SHT40 basic driver
Basic library for Adafruit SHT40 Working on PSoC6 Pioneer dev board CY8CKIT-062-WIFI-BT
Diff: SHT40.cpp
- Revision:
- 0:c46b3e0a8c2b
- Child:
- 1:c6381a3f2d9a
diff -r 000000000000 -r c46b3e0a8c2b SHT40.cpp --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/SHT40.cpp Mon Feb 07 15:08:07 2022 +0000 @@ -0,0 +1,85 @@ +/** + * @author Andrew Reed + * + * Freeware -- + * simple driver hacked together by hardware engineer, definite scope for + * improvement by someone who knows waht they are doing. + * + * @section DESCRIPTION + * + * SHT40 i2c Humidity and Temperature sensor. + * + * Datasheet, specs, and information: + * + * https://www.adafruit.com/product/4885 + */ + +/** + * Includes + */ +#include "SHT40.h" + +SHT40::SHT40(PinName sda, PinName scl) { + + i2c_ = new I2C(sda, scl); + //400KHz, as specified by the datasheet. + i2c_->frequency(I2C_SPEED_FAST); + + + +} + +int SHT40::tempC(void) { + + char txBuff[2]; + char rxBuff[6]; + + txBuff[0] = SHT4x_NOHEAT_HIGHPRECISION; // Triggers a temperature measure by feeding correct opcode. + txBuff[1] = SHT4x_NOHEAT_HIGHPRECISION >> 8; + i2c_->write((SHT40_I2C_ADDRESS << 1) & 0xFE, txBuff, 2); + thread_sleep_for(50); // Per datasheet, wait long enough for device to sample temperature + + // Reads triggered measure + i2c_->read((SHT40_I2C_ADDRESS << 1) | 0x01, rxBuff, 6); + thread_sleep_for(1); + + // Algorithm from arduino sht4x.h to compute temperature. + unsigned int rawTemperature = ((unsigned int) rxBuff[0] << 8) | (unsigned int) rxBuff[1]; + rawTemperature &= 0xFFFC; + + float tempTemperature = rawTemperature / (float)65536; //2^16 = 65536 + float realTemperature = -46.85 + (175.72 * tempTemperature); //From page 14 + + return (int)realTemperature; + +} +int SHT40::relHumid(void) { + + char txBuff[2]; + char rxBuff[6]; + + + txBuff[0] = SHT4x_NOHEAT_HIGHPRECISION; // send command. + txBuff[1] = SHT4x_NOHEAT_HIGHPRECISION >> 8; + i2c_->write((SHT40_I2C_ADDRESS << 1) & 0xFE, txBuff, 2); + thread_sleep_for(16); // delay to sample humidity + + // Reads measurement + i2c_->read((SHT40_I2C_ADDRESS << 1) | 0x01, rxBuff, 6); + thread_sleep_for(1); + + //Algorithm from sht4x.h. + unsigned int rawHumidity = ((unsigned int) rxBuff[3] << 8) | (unsigned int) rxBuff[4]; + + rawHumidity &= 0xFFFC; //Zero out the status bits but keep them in place + + //Convert to relative humidity + float RH = rawHumidity / (float)65536; // two bytes worth to float + float rh = -6 + (125 * RH); // adjustment values as per sht4x.h + rh = min(max(rh, (float)0.0), (float)100.0); + + + return (int)rh; + +} +