Configuration
The tea maker will be assessed whether it can successfully prepare tea within an acceptable time interval (<20 min), by following the brewing temperature and time for the selected type of tea. A good communication between the web interface and the machine should be established. The permitted latency between physical event and output (i.e. user input to machine activation) should be so that it allows a response for a cup of tea to be completed in the 20 min time interval. Thus the maximum latency should be <1s.
The data flow from the hardware to the web interface is illustrated in the data flow diagram:
The web interface interacts with the RPI through the server. When the user activates the web interface the RPI checks the input from the float switch to check whether there is water so that it prompts the user to proceed with parameter selection. Then the parameters are send from the web interface to the RPI which in turn activates the heating element. The digital temperature sensor communicates with the RPI using 1-wire communication protocol, sending information on the temperature of the water. The sensor provides 9-bit to 12-bit temperature measurements with a latency of 93.75 ms for the lower bit values and 750 ms for the higher ones.
The workflow is illustrated below:
