The most convenient way to communicate with a device on a network is through a web browser. The Raspberry Pi runs a Lighttpd web server which serves the web pages. This leads to the question of device access to the charge controller which is easily solved with the help of python-serial. Two of the DIP switches on the LCD board are used to configure the way the PWM percentage is controlled:
- serial port
In serial mode, a command is sent to the charge controller through the serial port which sets the PWM percentage and thus the voltage and the load on the solar panels. The web page has an interface to set the PWM. The ability to vary the PWM manually with a remote interface makes it easier to test the MPPT algorithm. The MPPT algorithm should automatically find the correct PWM for the maximum power point, and by switching to manual mode under the same conditions and finding the maximum power point manually, we can verify the MPPT operation.