Low pass filter configuration using the Commander

When using a standard callback for LowPassFilter class:commander.lpf(&lpf,cmd) the user will have available a command:

• F: Low pass filter time constant

For example if you have a low pass filter added to the commander:

LowPassFilter filter = ....
Commander commander = ...

void onLpf(char* cmd){ commander.lpf(&filter,cmd); }
void setup(){
  ...
  commander.add('A',onLpf,"my lpf");
  ...
}
void loop(){
  ...
  commander.run();
}

You will be able to configure (set and get) its parameters from serial monitor:

$ AF           # get time constant
Tf: 1.0
$ AF0.05       # set time constant
Tf: 0.05
$ AW           # unknown command
err