SHT3x - Temperature and rH
Description
Library for SHT3x family (SHT30, SHT31, SHT33, SHT35) of I2C temperature and relative humidity sensors.
The SHT3x is a fully calibrated, linearised and temperature compensated temperature and humidity sensor.
- I2C interface with communication speed up to 1 MHz
- Two user selectable addresses (chosen by chip pin)
- Temperature range: -40 to 125°C ±0.2°C (SHT33: ±0.48°C, SHT35: ±0.1°C)
- Relative humidity range: 0..100%rH ±2%rH (SHT35: ±1.5%rH)
OVERVIEW
SHT3x_Ab1stract:
This library can be used to handle SHT3x family (SHT30, SHT31, SHT33, SHT35) I2C temperature and relative humidity sensors.
Interfaces: 1x I2C
The SHT3x is a fully calibrated, linearised and temperature compensated temperature and humidity sensor.
At least firmware version 01v012 is required for use with a rapidM2M M23.
SHT3x_How_to_use:
/* Hardware setup - as used on the "rapidM2M Base Starter" */
const
{
PORT_I2C = 0, // The first I2C interface should be used.
ADDRPIN = 0, // Logic level of the chip's address pin
// (either 0^="Low" or 1=^"High")
}
/* Control structures for available sensors */
static sht3x[TSHT3x]; // Control structure to manage the SHT3x
/* 1 sec. timer is used for the general program sequence */
#callback MainTimer()
{
// Init with "open loop" value to identify missing measurements
// (temp/rH simply stay unchanged in case of an error)
static temp_ = S32_OL; // Temperature read from the SHT31
static rh_ = S32_OL; // Humidity read from the SHT31
new err= SHT3x_read( sht3x, temp_, rh_); // reads the measured values from the SHT3x
// Issues temperature, humidity and return value of the SHT3x_read function via the watch panel
#watch( "temp_rh=%s°C %s%% %s", s32ToNamurStr( temp_,1), s32ToNamurStr( rh_), errorToStr( err));
}
/* Application entry point */
main()
{
// Inits the I2C interface
catch( rM2M_I2cInit( PORT_I2C, SHT3x_CLOCK, 0));
// Inits SHT3x and starts first measurement ("SHT3x_MODE_INTERLACED" is the default mode)
catch( SHT3x_open( sht3x, PORT_I2C, ADDRPIN));
// Initialisation of a cyclic sec. timer
setInterval(MainTimer, 1000);
}
BASIC
SHT3x_CLOCK -
typical I2C clock speed to be used
SHT3x_MODE_x:
operation mode for SHT3x
SHT3x_MODE_INTERLACED - interlaced on-demand measurements (default: High quality)
The first capture starts with SHT3x_open(), then immediately after each SHT3x_read().
SHT3x_MODE_INST - instant on-demand measurements (default: Low quality)
Measurement is captured in front of each SHT3x_read().
SHT3x_MODE_CONT_100 - continous background measurement with 100ms period (default: Low quality)
SHT3x_MODE_CONT_250 - continous background measurement with 250ms period (default: Medium quality)
SHT3x_MODE_CONT_500 - continous background measurement with 500ms period (default: High quality)
SHT3x_MODE_CONT_1000 - continous background measurement with 1000ms period (default: High quality)
SHT3x_MODE_CONT_2000 - continous background measurement with 2000ms period (default: High quality)
Applies to all SHT3x_MODE_CONT_x modes:
Measurements are captured periodically in the background. The SHT3x_read() simply reads the last captured values.Plus: Values are up-to-date without any waiting time in SHT3x_read() Minus: Maximum power consumption by the chip Best to use for long or varying read intervals if power consumption is not an affair
The SHT3x_MODE_CONT_x must be shorter than the read interval - otherwise SHT3x_read() may fail with ERROR_DONE.
Applies to all modes:
Quality flags (SHT3x_MODE_Qx) can optionally be used to choose another than the default quality
SHT3x_open( ..., SHT3x_MODE_CONT_500 | SHT3x_MODE_QL)
Example in SHT3x_How_to_use
SHT3x_MODE_CONT_x:
see SHT3x_MODE_x
SHT3x_MODE_Qx:
Flags to specify the quality for the measurements of the SHT3x
The Quality flags can optionally be used to select a quality other than the default quality specified for the selected operation mode (SHT3x_MODE_x).
SHT3x_open( ..., SHT3x_MODE_CONT_500 | SHT3x_MODE_QL)
SHT3x_MODE_QL - low repeatability of typ. 0.15 °C / 0.21 %rH,
<4ms durationSHT3x_MODE_QM - medium repeatability of typ. 0.08 °C / 0.15 %rH,
<6ms durationSHT3x_MODE_QH - high repeatability of typ. 0.04 °C / 0.08 %rH,
<15ms duration
SHT3x_open(sht3x, i2c, addrpin, mode=SHT3x_MODE_INTERLACED)
initializes the SHT3x
Reads serial number and starts measurement (if not SHT3x_MODE_INST chosen). If the SHT3x has already been initialized, beforehand any running measurements are stopped and a soft reset is performed.
sht3x : TSHT3x - empty control block
i2c : s32 - I2C interface where SHT3x is connected to
The I2C interface must be initialisation before using rM2M_I2cInit().
addrpin : TpinValue - Logic level at the chip's address pin (either 0 for "Low" or 1 for "High")
0 - I2C address A (0x44) should be used
1 - I2C address B (0x45) should be used
mode - operation mode / quality flags ( SHT3x_MODE_x | SHT3x_MODE_Qx )
returns : Terror
ERROR - Invalid I2C interface or I2C interface not opened yet
ERROR_DONE - NACK detected (i.e. SHT3x not ready)
ERROR_CRC - CRC check failed
ERROR_TIMEOUT - Timeout when accessing the SHT3x
< OK - If another error occurs
Example in SHT3x_How_to_use
SHT3x_close(sht3x[TSHT3x])
closes SHT3x and grants minimum power consumption
It stops any periodic measurement and performs a soft reset. The soft reset also turns off the heater.
sht3x : TSHT3x - Control block of a specific SHT3x (Initialized by SHT3x_open() )
returns : s32
OK - if successful
ERROR_DONE - NACK detected (i.e. SHT3x not ready)
ERROR_CRC - CRC check failed
ERROR_TIMEOUT - Timeout when accessing the SHT3x
< OK - If another error occurs
SHT3x_read(sht3x, &temp, &rh)
reads the measured values from the SHT3x.
SHT3x_Ab1stract for range and resolution.
Depending on the operating mode (SHT3x_MODE_x) set using SHT3x_open(), further actions are carried out:SHT3x_MODE_INTERLACED - A new measurement is triggered after reading SHT3x_MODE_INST - The measurement will be triggered before reading. The function then waits until the measurement has been performed.
Only then can the measured values be returned.
sht3x : TSHT3x - Control block of a specific SHT3x (Initialized by SHT3x_open() )
temp : s32 - [0.1°C] Buffer for the temperature, unchanged if result < OK
rh : s32 - [1%] Buffer for the relative humidity, unchanged if result < OK
returns : Terror
OK - if successful
ERROR_DONE - NACK detected (i.e. SHT3x not ready)
When using one of the SHT3x_MODE_CONT_x modes, choose a faster mode or expand the interval between SHT3x_read().
ERROR_CRC - Either one or both values had CRC errors and may not be updated
ERROR_TIMEOUT - Timeout while waiting for the measurement to be completed in SHT3x_MODE_INST mode.
ERROR_CLOSED - No operating mode set
< OK - If another error occurs
Example in SHT3x_How_to_use
EXPERT
SHT3x_CLOCK_MAX -
absolute maximum I2C clock speed
SHT3x_STATUS_x:
result flags for SHT3x_readStatus()
SHT3x_STATUS_ALERT - bit 15: Alert pending status
0 - no pending alerts
1 - at least one pending alert
SHT3x_STATUS_HEATER - bit 13: Heater status
0 - Heater OFF
1 - Heater ON
SHT3x_STATUS_ALERT_RH - bit 11: RH tracking alert
0 - no alert
1 - alert
SHT3x_STATUS_ALERT_T - bit 10: T tracking alert
0 - no alert
1 - alert
SHT3x_STATUS_RESET - bit 4: System reset detected
0 - no reset detected since last ‘clear status register’ command
1 - reset detected (hard reset, soft reset command or supply fail)
SHT3x_STATUS_CMD_ERR - bit 1: Command status
0 - last command executed successfully
1 - last command not processed. It was either invalid, failed the integrated command checksum
SHT3x_STATUS_WR_ERR - bit 0: Write data checksum status
0 - checksum of last write transfer was correct
1 - checksum of last write transfer failed
SHT3x_readStatus(const sht3x[TSHT3x])
reads status register of the SHT3x
sht3x : TSHT3x - Control block of a specific SHT3x (Initialized by SHT3x_open() )
returns : Terror
>= 0 - SHT3x_STATUS_x flags
ERROR_DONE - NACK detected (i.e. SHT3x not ready)
ERROR_CRC - CRC check failed
< OK - if another error occurs
DEBUG
SHT3x_dumpStatus(sht3x[TSHT3x], const prefix{}="SHT3x_dumpStatus", forceDump=0)
issues current status (contents of the status register or errors when accessing the register) via the console if it has changed since the last call of this function
sht3x : TSHT3x - Control block of a specific SHT3x (Initialized by SHT3x_open() )
prefix : astr - Some text to print in front of the status
forceDump : bool - Issue current status via the console ...
true - in any case (if it changed or not)
falese - only if it has changed since the last call
returns : Terror
>= 0 - SHT3x_STATUS_x flags
ERROR_DONE - NACK detected (i.e. SHT3x not ready)
ERROR_CRC - CRC check failed
< OK - if another error occurs