SmartMeter Readout

Smart Meter Readout is a Python script that periodically reads values from a KAIFA CL101 Smartmeter from VKW using the MBUS customer interface. It was tested on a RaspberryPi Zero W with an MBus adapter. The received values are stored in a local SQLite database for efficient querying and data management.

Detailed Description and required Hardware

A detailed description of the project and the required hardware can be found on my blog.

Setup

The setup uses pypy to execute the script for better performance.

Prerequisites

First, install the required system packages:

# Update package list
sudo apt update

# Install PyPy3 and pip
sudo apt install pypy3 pypy3-dev pypy3-venv

# Install pip for PyPy3 if not already available
sudo apt install pypy3-pip

# Install git to clone the repository
sudo apt install git

Setup tmpfs for reduced SD card wear

To minimize SD card wear, the database runs in RAM with periodic backups to persistent storage:

# Create the tmpfs directory
sudo mkdir /ram
sudo chmod a+rw /ram

# Edit /etc/fstab to add tmpfs mount
echo "tmpfs    /ram    tmpfs    defaults,noatime,nosuid,nodev,noexec,mode=1777,size=8M  0  0" | sudo tee -a /etc/fstab

# Reboot to activate tmpfs
sudo reboot now

Installation

1. Clone the repository:

   cd /home/pi
   git clone https://github.com/PhilippSev/SmartMeterReadout.git
   cd SmartMeterReadout

2. Create the data directory:

   sudo mkdir -p /home/pi/smartmeter_data
   sudo chown pi:pi /home/pi/smartmeter_data

3. Create the service directory:

   sudo mkdir -p /home/pi/readout
   sudo chown pi:pi /home/pi/readout

4. Copy files to service directory:

   cp SmartMeterReadout.py /home/pi/readout/
   cp query_database.py /home/pi/readout/
   cp requirements.txt /home/pi/readout/
   cp smartmeterreadout.service /home/pi/readout/
   cp createService.sh /home/pi/readout/

Key

The SmartMeter requires a key to access. This key is stored in the file key.txt which is excluded from the repository.

Create the key file:

# Create the key file in the service directory
echo "YOUR_SMARTMETER_KEY_HERE" > /home/pi/readout/key.txt
# Replace YOUR_SMARTMETER_KEY_HERE with your actual 32-character hex key

Install python requirements

In order for the systemd service to be able to execute the script the requirements must be installed for all users on the system.

sudo pypy3 -mpip install -r requirements.txt

Setup as Systemd Service

The Setup as systemd service is done by executing the createService script. This script expects the required files to be placed in /home/pi/readout

cd /home/pi/readout
sudo ./createService.sh

After setting up the service, you can control it with:

# Start the service
sudo systemctl start smartmeterreadout

# Enable autostart on boot
sudo systemctl enable smartmeterreadout

# Check service status
sudo systemctl status smartmeterreadout

# View service logs
sudo journalctl -u smartmeterreadout -f

Hardware Setup

Make sure your hardware is properly configured:

1. Serial Interface: Enable the serial interface on your Raspberry Pi

   sudo raspi-config
   # Go to Interfacing Options > Serial > Enable

2. MBus Connection: Connect your MBus adapter to the Raspberry Pi's serial pins

   • The script uses /dev/ttyS0 by default
   • Make sure the pi user has access to the serial port:

     sudo usermod -a -G dialout pi

3. Test Connection: You can test if the smart meter is responding:

   # Check if the serial device exists
   ls -l /dev/ttyS0
   
   # Test basic serial communication (optional)
   sudo cat /dev/ttyS0

Troubleshooting

Permission Issues:

# Make sure all scripts are executable
chmod +x /home/pi/readout/*.py
chmod +x /home/pi/readout/createService.sh

# Check serial port permissions
ls -l /dev/ttyS0
sudo usermod -a -G dialout pi
# Logout and login again for group changes to take effect

Service Issues:

# Check if service is running
sudo systemctl status smartmeterreadout

# Restart service
sudo systemctl restart smartmeterreadout

# Check logs for errors
sudo journalctl -u smartmeterreadout --no-pager -l

Database Issues:

# Check if database directory exists and is writable
ls -la /home/pi/smartmeter_data/

# Test database connection
cd /home/pi/readout
python3 query_database.py current

Using the Database

Direct Database Access

You can query the database directly using the included query script:

# Show current reading summary
python3 query_database.py current

# Show history for last 24 hours
python3 query_database.py history

# Show history for last 48 hours  
python3 query_database.py history 48

# Show raw current data
python3 query_database.py raw-current

# Show raw history data
python3 query_database.py raw-history 24

Database Schema

The SQLite database contains two main tables:

current_readings: Stores the latest meter readings

• timestamp, meter_number, logical_device_name
• wirkenergie_bezug/lieferung (energy consumption/production)
• wirkleistung_bezug/lieferung (power consumption/production)
• spannung_l1/l2/l3 (voltage for each phase)
• strom_l1/l2/l3 (current for each phase)
• blindenergie_bezug/lieferung (reactive energy)
• leistungsfaktor (power factor)

history: Stores historical energy readings over time

• timestamp
• wirkenergie_bezug/lieferung (total energy consumption/production in Wh)

Disk Usage

The SQLite database runs in tmpfs (/ram/) to minimize SD card wear, with automatic backups to persistent storage (/home/pi/smartmeter_data/) every 5 minutes. This approach provides:

• Reduced SD card wear: Database operations happen in RAM
• Data persistence: Regular backups ensure data is not lost
• Performance: RAM-based database operations are faster
• Reliability: System can recover from unexpected reboots using the latest backup

The tmpfs is limited to 8MB, which is sufficient for the database size and prevents excessive RAM usage.