Data logging code for the Raspberry Pi Weather Station HAT

1. Start with a fresh install of Raspbian. Boot up as per usual and expand the filesystem to fill the SD card.
2. Un-blacklist the I²C module.

sudo nano /etc/modprobe.d/raspi-blacklist.conf

Comment out the line blacklist i2c-bcm2708 by putting a hash # at the start of the line.

Press Ctrl - O then Enter to save and Ctrl - X to quit nano.

1. Set the required modules to load automatically on boot.

sudo nano /etc/modules

Add the following lines to the bottom of the file:

i2c-dev
rtc_pcf8523
w1-gpio
w1-therm

Press Ctrl - O then Enter to save and Ctrl - X to quit nano.

1. Reboot for these changes to take effect.

sudo reboot

1. Ensure that a CR/BR1225 3 volt coin cell battery has been inserted. Positive + side facing up.
2. Enable the Real Time Clock (RTC). First drop into root:

sudo -s

Enable the RTC:

echo "pcf8523 0x68" > /sys/class/i2c-adapter/i2c-1/new_device

Check that that it now appears in /dev

ls /dev/rtc*

Expected result: /dev/rtc0

Press Ctrl - D to come out of root.

1. Initialise the RTC with the correct time.

Use the date command to check the current system time is correct. If correct then you can set the RTC time from the system clock with the following command:

sudo hwclock -w

If not then you can set the RTC time manually using the command below (you'll need to change the --date parameter, this example will set the date to the 1st of January 2014 at midnight):

sudo hwclock --set --date="2014-01-01 00:00:00" --utc

Then set the system clock from the RTC time.

sudo hwclock -s

You can passively display the time in the RTC using: sudo hwclock -r

1. Enable loading the RTC driver and setting the system clock at boot time.

sudo nano /etc/rc.local

Insert the following lines before exit 0 at the bottom of the file:

echo "pcf8523 0x68" > /sys/class/i2c-adapter/i2c-1/new_device
sleep 2
echo "Setting System clock from RTC..."
hwclock -s
hwclock -r

Press Ctrl - O then Enter to save and Ctrl - X to quit nano.

1. Install the necessary software packages.

sudo apt-get update
sudo apt-get install i2c-tools python-smbus telnet apache2 mysql-server python-mysqldb php5 libapache2-mod-php5 php5-mysql -y

This will take some time. You will be prompted to create and confirm a password for the root user of the MySQL database server.

1. Create the database within MySQL.

mysql -u root -p

Enter the password that you chose during installation.

You'll now be at the MySQL prompt mysql>, first create the database:

CREATE DATABASE weather;

Expected result: Query OK, 1 row affected (0.00 sec)

Switch to that database:

USE weather;

Expected result: Database changed

Create the table that will store all of the weather measurements:

CREATE TABLE WEATHER_MEASUREMENT(
  ID BIGINT NOT NULL AUTO_INCREMENT,
  REMOTE_ID BIGINT,
  AMBIENT_TEMPERATURE DECIMAL(6,2) NOT NULL,
  GROUND_TEMPERATURE DECIMAL(6,2) NOT NULL,
  AIR_QUALITY DECIMAL(6,2) NOT NULL,
  AIR_PRESSURE DECIMAL(6,2) NOT NULL,
  HUMIDITY DECIMAL(6,2) NOT NULL,
  WIND_DIRECTION DECIMAL(6,2) NULL,
  WIND_SPEED DECIMAL(6,2) NOT NULL,
  WIND_GUST_SPEED DECIMAL(6,2) NOT NULL,
  RAINFALL DECIMAL (6,2) NOT NULL,
  CREATED TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
  PRIMARY KEY ( ID )
);

Expected result: Query OK, 0 rows affected (0.05 sec)

Press Ctrl - D or type exit to quit MySQL.

1. Remove the fake hardware clock package.

sudo update-rc.d fake-hwclock remove
sudo apt-get remove fake-hwclock -y

1. Test that the I²C devices are online and working.

sudo i2cdetect -y 1

Expected output:

     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: 40 -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- UU 69 -- -- -- -- -- --
70: -- -- -- -- -- -- -- 77

• 40 = HTU21D. Humidity and temperature sensor.
• 77 = BMP180. Barometric pressure sensor.
• 68 = PCF8523. Real Time Clock, it will show as UU because it's reserved by the driver.
• 69 = MCP3427. Analogue to Digital Converter.

Note: 40 and 77 will only show if you have connected the AIR board to the main board.

1. Download the data logging code.

cd ~
git clone https://github.com/raspberrypi/weather-station.git

This will create a new folder in the home directory called weather-station.

1. Start the Weather Station daemon and test it.

sudo ~/weather-station/interrupt_daemon.py start

Expected result: PID: 2345 (your number will be different)

A continually running process is required to monitor the rain gauge and the anemometer. These are reed switch sensors and the code uses interrupt detection. These interrupts can occur at any time as opposed to the timed measurements of the other sensors. You can use the telnet program to test or monitor it.

telnet localhost 49501

Expected result:

Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
OK

The following text commands can be used:

• RAIN: displays rainfall in ml
• WIND: displays average wind speed in kph
• GUST: displays wind gust speed in kph
• RESET: resets the rain gauge and anemometer interrupt counts to zero
• BYE: quits

Use the BYE command to quit.

1. Set the Weather Station daemon to automatically start at boot time.

sudo nano /etc/rc.local

Insert the following lines before exit 0 at the bottom of the file:

echo "Starting Weather Station daemon..."
/home/pi/weather-station/interrupt_daemon.py start

1. If you wish you can register your Weather Station with a cloud based Oracle database so that your data can be used by other schools.

Oracle Apex Database

You will need to complete a form whereupon you must wait for a Raspberry Pi admin to approve your school in the database. Once approved an activation email will be sent to you containing a verification code. Log in using your school name for the username and the password that you chose. You will then be prompted for the verification code from the email.

Many weather stations can belong to one school. Once you have logged in you'll need to create a new weather station under your school. The latitude and longitude of the weather station will be required for this. Once you have created a weather station it will have its own password automatically generated, this is used by the weather station itself when it uploads the measurements to Oracle and is separate to your school login.

Note: There is a known bug here where the Add Weather Station screen does not show a Create button, but only a Return button on the right. If you experience this just log out and back in and that should fix it.

1. Add the weather station name and password to the local Oracle credentials file. This allows the code that uploads to Oracle to know what credentials to use.

cd ~/weather-station

nano credentials.oracle.template

Replace the name and key parameters with the Weather Station Name and Passcode of the weather station as specified in Oracle (under Home > Weather Stations). The double quotes " enclosing these values in this file are important so take care not to remove them by mistake.

Press Ctrl - O then Enter to save and Ctrl - X to quit nano.

1. Rename the Oracle credentials template file to enable it.

mv credentials.oracle.template credentials.oracle

1. Update the to the local MySQL credentials file with the password for the MySQL root user that you chose during installation.

nano credentials.mysql

The PASSWORD field is probably the only one you need to change (unless you also chose raspberry). The double quotes " enclosing the values are important so take care not to remove them by mistake.

Press Ctrl - O then Enter to save and Ctrl - X to quit nano.

1. The main entry points for the code are log_all_sensors.py and upload_to_oracle.py. These will be called by the cron scheduler to automatically take measurements. The measurements will be saved in the local MySQL database as well as uploaded to the Oracle Apex Database online (if you registered).

The template crontab file crontab.save is provided as a default. If you wish to change the measurement or upload frequency then edit this file before going onto the next step:

nano crontab.save

Press Ctrl - O then Enter to save and Ctrl - X to quit nano when you're done.

1. Heads up! At this point you may wish to stop and check out the Weather Station scheme of work (here).
2. Enable cron to automatically start taking measurements, also known as data logging mode.

crontab < crontab.save

Your weather station is now live and recording data at timed intervals.

You can disable data logging mode at any time by removing the crontab with the command below:

crontab -r

To enable data logging mode again use the command below:

crontab < ~/weather-station/crontab.save

Note: Do not have data logging mode enabled while you're working through the data Collection lessons in the scheme of work.

1. You can manually cause a measurement to be taken at any time with the following command:

sudo ~/weather-station/log_all_sensors.py

Don't worry if you see Warning: Data truncated for column X at row 1, this is expected.

1. You can manually trigger an upload too with the following command:

sudo ~/weather-station/upload_to_oracle.py

1. You can also view the data in the database using the following commands:

mysql -u root -p

Enter the password. Then switch to the weather database:

USE weather;

Run a select query to return the contents of the WEATHER_MEASUREMENT table.

SELECT * FROM WEATHER_MEASUREMENT;

After a lot of measurements have been recorded it will be sensible to use the SQL where clause to only select records that were created after a specific date and time:

SELECT * FROM WEATHER_MEASUREMENT WHERE CREATED > '2014-01-01 12:00:00';

Press Ctrl - D or type exit to quit MySQL.

1. Go here to download and install the demo website.