pi-sht1x 1.0.4

Python 3 library for Sensirion SHT1x series of temperature & humidity sensors for the Raspberry Pi.

pi-sht1x
--------

The pi-sht1x package is a Python 3 library used to communicate and
control the Sensirion SHT1x series of temperature and humidity sensors.
It was designed to be used primarily with the Raspberry Pi and depends
on the `RPi.GPIO <http://pypi.python.org/pypi/RPi.GPIO>`_ library.

SHT1x (including SHT10, SHT11 and SHT15) is Sensirion’s family of
surface mountable relative humidity and temperature sensors. The sensors
integrate sensor elements plus signal processing on a tiny foot print
and provide a fully calibrated digital output. A unique capacitive
sensor element is used for measuring relative humidity while temperature
is measured by a band-gap sensor.

The package was tested using the Raspberry Pi B+ and Raspberry Pi 2.
There shouldn't be issues running this on the older models, but no
guarantees. If you do run into any problems, please let me know or
create an
`issue <https://bitbucket.org/drohm/pi-sht1x/issues?status=new&status=open>`_
on the Bitbucket project page:
::
https://bitbucket.org/drohm/pi-sht1x

The data sheet for the SHT1x series of sensors can be found here:

::

http://bit.ly/1Pafs6j

This library provides the following functionality:

- Taking temperature measurements
- Taking humidity measurements
- Make dew point calculations
- Change the supplied voltage (5V, 4V, 3.5V, 3V, 2.5V)
- Enable or disable CRC checking
- Reading the Status Register
- Writing to the Status Register, provides the following functionality:

- Turn ``otp_no_reload`` on (will save about 10ms per measurement)
- Turn on the internal heater element (for functionality analysis,
refer to the data sheet list above for more information)
- Change the resolution of measurements, High (14-bit temperature
and 12-bit humidity) or Low (12-bit temperature and 8-bit
humidity)

--------------

Installation
------------

Installation is pretty simple:

::

pip3 install pi-sht1x

Note that to install packages into the system-wide PATH and
site-packages, elevated privileges are often required (sudo). Use
``install –user`` or
`virtualenv <https://pypi.python.org/pypi/virtualenv>`_ to do
unprivileged installs.

Usage
-----

When instantiating a SHT1x object, the following default values are used
if not specified:

::

gpio_mode: GPIO.BOARD
vdd: 3.5V
resolution: High (14-bit temperature & 12-bit humidity)
heater: False
otp_no_reload: False
crc_check: True

Command Line
~~~~~~~~~~~~

You can invoke the SHT1x class directly from the REPL. In order to use
the library you need to import the package:

::

from pi_sht1x import SHT1x

Now you can create the sensor object and take measurements:

::

with SHT1x(18, 23, gpio_mode=GPIO.BCM) as sensor:
temp = sensor.read_temperature()
humidity = sensor.read_humidity(temp)
sensor.calculate_dew_point(temp, humidity)
print(sensor)

This will create the SHT1x object using ``data_pin=18``, ``sck_pin=23``,
``gpio_mode=GPIO.BCM``, and default values for ``vdd`` (3.5V),
``resolution`` (High), ``heater`` (False), ``otp_no_reload`` (False),
and ``crc_check`` (True).

The output will look something like this:

::

Temperature: 24.05*C [75.25*F]
Humidity: 22.80%
Dew Point: 1.38*C

Note that this library should be used with a context manager like
the ``with`` statement. Using it with a context manager will allow
the program to properly clean up after itself and reset the GPIO
pins back to default states.

examples.py
~~~~~~~~~~~

This script, located in the examples folder, includes several ways to
use the SHT1x class to take temperature, humidity, and dew point
measurements. In order to use the script, be sure to update the
``DATA_PIN`` and ``SCK_PIN`` constants near the top of the file with the
pin numbers you're using locally in your setup:

::

DATA_PIN = 18
SCK_PIN = 23

Based on the data sheet, the recommended voltage for the SHT1x sensor is
3.3V. Based on that the default voltage, if not specified, is 3.5V. If
you're using 5V to power the sensor, be sure to set that value when
creating the object. To run the script:

::

sudo python3 examples/examples.py

Running the script exercises all of the functionality for the sensor. Be
sure to look through the script to see what you can do and how to
customize using the sensor. Sample output:

::

$ sudo python3 examples/examples.py
Test: using default values: 3.5V, High resolution, no heater, otp_no_reload off, CRC checking enabled...
Temperature: 24.49*C [76.04*F]
Humidity: 20.68%
Dew Point: 0.47*C

Temperature: 24.48*C [76.02*F]
Humidity: 20.68%
Dew Point: 0.46*C

Temperature: 24.47*C [76.01*F]
Humidity: 20.68%
Dew Point: 0.45*C

Temperature: 24.51*C [76.06*F]
Humidity: 20.68%
Dew Point: 0.47*C

Temperature: 24.51*C [76.06*F]
Humidity: 20.68%
Dew Point: 0.47*C
Test complete.

Test: reading all measurements using GPIO.BCM mode, 3V, High resolution, heater off, otp_no_reload off, and CRC check on.
Temperature: 24.48*C [76.02*F]
Humidity: 20.61%
Dew Point: 0.42*C

Temperature: 24.46*C [75.98*F]
Humidity: 20.61%
Dew Point: 0.40*C

Temperature: 24.46*C [75.98*F]
Humidity: 20.61%
Dew Point: 0.40*C

Temperature: 24.48*C [76.02*F]
Humidity: 20.68%
Dew Point: 0.46*C

Temperature: 24.48*C [76.02*F]
Humidity: 20.65%
Dew Point: 0.44*C
Test complete.
.
.
.

The `RPi.GPIO <http://pypi.python.org/pypi/RPi.GPIO>`_ module
requires root privileges in order to communicate with the GPIO pins
on the Raspberry Pi so you need to run your scripts as root (sudo).

sensor.py
~~~~~~~~~

This script is callable from the terminal and the sensor parameters are
passed into the script.

::

sudo python3 sensor.py 18 23 -g 'BCM'

This executes the sensor script using ``data_pin=18``, ``sck_pin=23``,
and ``gpio_mode=GPIO.BCM``. The script will then create an instance of
the SHT1x class and read in the temperature, humidity, and calculate the
dew point five times, sleeping 2 seconds in between each measurement.
The output will looks something like this:

::

$ sudo python3 examples/sensor.py 18 23 -g 'BCM'
Temperature: 24.05*C [75.25*F]
Humidity: 22.79%
Dew Point: 1.37*C

Temperature: 24.03*C [75.21*F]
Humidity: 22.79%
Dew Point: 1.36*C

Temperature: 24.01*C [75.16*F]
Humidity: 22.79%
Dew Point: 1.33*C

Temperature: 24.01*C [75.17*F]
Humidity: 22.86%
Dew Point: 1.38*C

Temperature: 24.02*C [75.19*F]
Humidity: 22.86%
Dew Point: 1.39*C

To get a listing of all the parameters you can provide to the script,
use ``python3 sensor.py -h`` for help:

::

$ sudo python3 examples/sensor.py -h
usage: sensor.py [-h] [-g {BCM,BOARD}] [-v {5V,4V,3.5V,3V,2.5V}]
[-r {HIGH,LOW}] [-e] [-o] [-c]
data-pin sck-pin

Reads the temperature and relative humidity from the SHT1x series of sensors
using the pi_sht1x library.

positional arguments:
data-pin Data pin used to connect to the sensor.
sck-pin SCK pin used to connect to the sensor.

optional arguments:
-h, --help show this help message and exit
-g {BCM,BOARD}, --gpio-mode {BCM,BOARD}
RPi.GPIO mode used, either GPIO.BOARD or GPIO.BCM.
Defaults to GPIO.BCM.
-v {5V,4V,3.5V,3V,2.5V}, --vdd {5V,4V,3.5V,3V,2.5V}
Voltage used to power the sensor. Defaults to 3.5V.
-r {HIGH,LOW}, --resolution {HIGH,LOW}
Resolution used by the sensor, 14/12-bit or 12-8-bit.
Defaults to High.
-e, --heater Used to turn the internal heater on (used for
calibration).
-o, --otp-no-reload Used to enable OTP no reload, will save about 10ms per
measurement.
-c, --no-crc-check Performs CRC checking.

--------------

Credits
-------

This module was done for fun and to learn how to communicate with serial
devices using Python and the Raspberry Pi. I referred to the following
projects from time to time when I hit a stumbling block (there were
many...):

- `Jonathan Oxer <https://github.com/practicalarduino/SHT1x>`_
- `Luca Nobili <https://bitbucket.org/lunobili/rpisht1x>`_

--------------