As a group assignment we have compared 3 programming platforms as interfaces, the first one has the linux environment in raspberry but with scracht.
The second one is the MIT APP INVENTOR, originally from the Scracht programming environment.
The other is the MBLOCK that uses the Scracht bases but oriented for the arduino.
And finally this FACILINO, environment with scracht but is very technical at the time of programming.
I have decided to use processing to make the interface.
Processing page has some examples and the most appropriate are those in the keyboard section. The template or example I have used is KEYBOARD FUNCTIONS.
I have modified the values of the original code to adapt it to my numerical keypad.
With the arduino SPARKFUN tutorial with processing. I followed them step by step in arduino IDE.
I have also added the configuration in the processing code since it is the one that will receive the data of the arduino IDE by serial.
Here is one of the part of the linking code of the two program
I had a problem at the beginning with the serial that I did not recognize it and the window of the freeze was freezing.
after finding the error, it was that the COM port is not properly assigned and could be compiled successfully.