Serge Sozonoff
Port of the SHT2x example code from Sensirion
Dependents: sht21_test ENVLogger
Diff: SHT2x.cpp
- Revision:
- 0:74df6ab91c79
- Child:
- 1:d0f691423bf1
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/SHT2x.cpp Sat Apr 23 14:08:11 2011 +0000
@@ -0,0 +1,239 @@
+//
+// S E N S I R I O N AG, Laubisruetistr. 50, CH-8712 Staefa, Switzerland
+//==============================================================================//
+// Project : SHT2x Sample Code (V1.2)
+// File : SHT2x.c
+// Author : MST
+// Controller: NEC V850/SG3 (uPD70F3740)
+// Compiler : IAR compiler for V850 (3.50A)
+// Brief : Sensor layer. Functions for sensor access
+//==============================================================================//
+//---------- Includes ----------------------------------------------------------
+#include "SHT2x.h"
+
+SHT2x::SHT2x (PinName p_sda, PinName p_scl) : i2c(p_sda, p_scl) {
+}
+
+SHT2x::SHT2x (I2C& p_i2c) : i2c(p_i2c) {
+}
+
+//==============================================================================//
+int SHT2x::SHT2x_CheckCrc(int data[], int nbrOfBytes, int checksum)
+//==============================================================================//
+{
+ int crc = 0;
+ int byteCtr;
+ //calculates 8-Bit checksum with given polynomial
+ for (byteCtr = 0; byteCtr < nbrOfBytes; ++byteCtr) {
+ crc ^= (data[byteCtr]);
+ for (int bit = 8; bit > 0; --bit) {
+ if (crc & 0x80) crc = (crc << 1) ^ POLYNOMIAL;
+ else crc = (crc << 1);
+ }
+ }
+ if (crc != checksum) return CHECKSUM_ERROR;
+ else return 0;
+}
+//===========================================================================//
+int SHT2x::SHT2x_ReadUserRegister(int *pRegisterValue)
+//===========================================================================//
+{
+ int checksum; //variable for checksum byte
+ int error=0; //variable for error code
+
+ i2c.start();
+ i2c.write(I2C_ADR_W);
+ i2c.write(USER_REG_R);
+
+ i2c.start();
+ i2c.write(I2C_ADR_R);
+
+
+ *pRegisterValue = i2c.read(1);
+
+ checksum=i2c.read(0);
+
+ error |= SHT2x_CheckCrc (pRegisterValue,1,checksum);
+
+ i2c.stop();
+ return error;
+}
+//===========================================================================//
+int SHT2x::SHT2x_WriteUserRegister(int *pRegisterValue)
+//===========================================================================//
+{
+ int error=0; //variable for error code
+ i2c.start();
+
+ i2c.write(I2C_ADR_W);
+ i2c.write(USER_REG_W);
+ i2c.write(*pRegisterValue);
+ i2c.stop();
+
+ return error;
+}
+//===========================================================================//
+int SHT2x::SHT2x_MeasureHM(etSHT2xMeasureType eSHT2xMeasureType, int *pMeasurand)
+//===========================================================================//
+{
+ int checksum; //checksum
+ int data[2]; //data array for checksum verification
+ int error=0; //error variable
+
+ //-- write I2C sensor address and command --
+ i2c.start();
+
+ i2c.write(I2C_ADR_W); // I2C Adr
+ switch (eSHT2xMeasureType) {
+ case HUMIDITY:
+ i2c.write(TRIG_RH_MEASUREMENT_HM);
+ break;
+ case TEMP :
+ i2c.write(TRIG_T_MEASUREMENT_HM);
+ break;
+ default:
+ break;
+ }
+ //-- wait until hold master is released --
+ i2c.start();
+ i2c.write(I2C_ADR_R);
+
+ //SCL=HIGH; // set SCL I/O port as input
+
+ //for (i=0; i<1000; i++) { // wait until master hold is released or
+ // DelayMicroSeconds(1000); // a timeout (~1s) is reached
+ // if (SCL_CONF==1) break;
+ //}
+
+ //-- check for timeout --
+ //if (SCL_CONF==0) error |= TIME_OUT_ERROR;
+//-- read two data bytes and one checksum byte --
+
+ data[0] = i2c.read(1);
+ data[1] = i2c.read(1);
+
+ *pMeasurand = data[0] << 8;
+ *pMeasurand |= data[1];
+
+ checksum = i2c.read(0);
+ //-- verify checksum --
+ error |= SHT2x_CheckCrc (data, 2, checksum);
+
+ i2c.stop();
+ return error;
+}
+//===========================================================================//
+int SHT2x::SHT2x_MeasurePoll(etSHT2xMeasureType eSHT2xMeasureType, int *pMeasurand)
+//===========================================================================//
+{
+ int checksum; //checksum
+ int data[2]; //data array for checksum verification
+ int error = 0; //error variable
+ int i = 0; //counting variableSample Code SHT21
+
+ //-- write I2C sensor address and command --
+ i2c.start();
+
+ i2c.write(I2C_ADR_W);
+ switch (eSHT2xMeasureType) {
+ case HUMIDITY:
+ i2c.write(TRIG_RH_MEASUREMENT_POLL);
+ break;
+ case TEMP:
+ i2c.write(TRIG_T_MEASUREMENT_POLL);
+ break;
+ default:
+ break;
+
+ }
+ //-- poll every 10ms for measurement ready. Timeout after 20 retries (200ms)--
+ do {
+ i2c.start();
+ wait_ms(10);
+ if (i++ >= 20) break;
+ } while (i2c.write(I2C_ADR_R) == 0);
+
+ if (i >= 20) error |= TIME_OUT_ERROR;
+
+ //-- read two data bytes and one checksum byte --
+ data[0] = i2c.read(1);
+ data[1] = i2c.read(1);
+
+ *pMeasurand = data[0] << 8;
+ *pMeasurand |= data[1];
+
+ checksum = i2c.read(0);
+ //-- verify checksum --
+ error |= SHT2x_CheckCrc (data,2,checksum);
+ i2c.stop();
+ return error;
+}
+//===========================================================================//
+int SHT2x::SHT2x_SoftReset()
+//===========================================================================//
+{
+ int error=0; //error variable
+ i2c.start();
+ error |= i2c.write(I2C_ADR_W); // I2C Adr
+ error |= i2c.write(SOFT_RESET); // Command
+ i2c.stop();
+ wait_ms(15);
+ return error;
+}
+//==============================================================================//
+float SHT2x::SHT2x_CalcRH(int u16sRH)
+//==============================================================================//
+{
+ float humidityRH; // variable for result
+ u16sRH &= ~0x0003; // clear bits [1..0] (status bits)
+ //-- calculate relative humidity [%RH] --
+ humidityRH = -6.0 + 125.0/65536 * (float)u16sRH; // RH= -6 + 125 * SRH/2^16
+ return humidityRH;
+}
+//==============================================================================//
+float SHT2x::SHT2x_CalcTemperatureC(int u16sT)
+//==============================================================================//
+{
+ float temperatureC; // variable for result
+ u16sT &= ~0x0003; // clear bits [1..0] (status bits)
+ //-- calculate temperature [°C] --
+ temperatureC= -46.85 + 175.72/65536 *(float)u16sT; //T= -46.85 + 175.72 * ST/2^16
+ return temperatureC;
+}
+//==============================================================================//
+int SHT2x::SHT2x_GetSerialNumber(int u8SerialNumber[])
+//==============================================================================//
+{
+ int error=0; //error variable
+ //Read from memory location 1
+ i2c.start();
+ error |= i2c.write(I2C_ADR_W);
+ error |= i2c.write(0xFA); //Command for readout on-chip memory
+ error |= i2c.write(0x0F); //on-chip memory address
+ i2c.start();
+ error |= i2c.write(I2C_ADR_R); //I2C address
+ u8SerialNumber[5] = i2c.read(1); //Read SNB_3
+ i2c.read(1); //Read CRC SNB_3 (CRC is not analyzed)
+ u8SerialNumber[4] = i2c.read(1); //Read SNB_2
+ i2c.read(1); //Read CRC SNB_2 (CRC is not analyzed)
+ u8SerialNumber[3] = i2c.read(1); //Read SNB_1Sample Code SHT21
+ i2c.read(1); //Read CRC SNB_1 (CRC is not analyzed)
+ u8SerialNumber[2] = i2c.read(1); //Read SNB_0
+ i2c.read(0); //Read CRC SNB_0 (CRC is not analyzed)
+ i2c.stop();
+ //Read from memory location 2
+ i2c.start();
+ error |= i2c.write(I2C_ADR_W); //I2C address
+ error |= i2c.write(0xFC); //Command for readout on-chip memory
+ error |= i2c.write(0xC9); //on-chip memory address
+ i2c.start();
+ error |= i2c.write(I2C_ADR_R); //I2C address
+ u8SerialNumber[1] = i2c.read(1); //Read SNC_1
+ u8SerialNumber[0] = i2c.read(1); //Read SNC_0
+ i2c.read(1);
+ u8SerialNumber[7] = i2c.read(1); //Read SNA_1
+ u8SerialNumber[6] = i2c.read(1); //Read SNA_0
+ i2c.read(0); //Read CRC SNA0/1 (CRC is not analyzed)
+ i2c.stop();
+ return error;
+}
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