Sensirion_SDP31

Read-out the Sensirion SDP3x digital differetial pressure sensor by use of the I2C port on a Raspberry PI model 3B+. More info on the SDP3x sensor and the I2C port.

Raspberry PI - I2C port

First the hardware needs to be enabled before the software, attached python scripts, can be used. This is done by following the steps of the link above. The I2C port is not enabled by default, this needs to be done;

1. Run, in terminal, sudo raspi-config.
2. Select point 9, Advanced options.
3. Select A7, I2C, and select yes.
4. Exit this window and reboot the PI.

After reboot, check if the I2C port is enabled by using;

ls /dev/*i2c*

if I2C port is open the PI will respond with;

/dev/i2c-1

where 1 indicates which I2C bus is used.

Now the I2C port is enabled but to have interaction between the PI and the sensor some utilities are needed. Use the following command line in a terminal;

sudo apt-get install -y i2c-tools

The i2cdetect command probes all the addresses on a I2C port bus, and report whether any devices are present. Outcome of this command will look like;

pi@raspberrypi:~/$ i2cdetect -y 1
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- 21 -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --

Here the I2C adress of the sensor is 0x21. More information, or source, can be found here.

I2C - Python

To read out the sensors with python, some python modules are needed. Run the command lines below;

sudo apt-get update
sudo apt-get install python-smbus
sudo apt-get install python-obspy

Python scripts - simple script

To read out single/one shot data, use the simple scrip.

Python scripts - src

The sdp31.py script is the data request script, which loops over a specific time interval with a sample rate. This script uses the defenitions of sdp31_main.py, which defines all needed functions/defenitions. To use, the script need some arguments which will be listed by the help function (-h);

-t       - Time of recording
-fs      - Sampling rate

Author

Olivier den Ouden - KNMI - HFSP SeabirdSound