Small update to the Step Attenuator

When I first built the step attenuator,  I wanted it to check  linearity of amplifier stages.  I only needed a relative change in the insertion loss of the attenuator.  Recntly I was able to use my NanoVNA to measure the actual insertion loss across the total frequency range I am interested in.  I also received some questions about showing the actual insertion loss instead of the relative value,

Because of this I made a change to the code to switch the display value from relative to actual by a long press of the encoder knob.

       

 First I added some definitions and variables

float InsertionLoss = 2.6;  //insertion loss of attenuator at 0 dB 

int InLossMode  = 0;       // actual insertion loss or relative

#define ActualLoss  0   // display  value selected actual +                                  //insertion loss 

#define RelLoss     1   // display just value                                                //selected without insertion loss

The code to read the button push was modified to also check for a long press if you want to change display mode to show the actual insertion loss.

  // check button for display mode and step size

  read_btn();

  if (button) {

    if (button == SHORT_PRESS ) { //  toggle step size

      if (AttenStep == 1) AttenStep = 10;

      else AttenStep = 1;

      button = 0;

    }

    else {         // toggle insertion loss display type

      if (InLossMode == ActualLoss) InLossMode = RelLoss ;

      else InLossMode = ActualLoss;

      button = 0;

    }

  }

The display routine was modified to show th display value depnding on the InLossMode variable,

  if (InLossMode == ActualLoss) {    // show actual insertion loss

    display.setTextSize(1);

    display.setCursor(20, 15);

    display.print("Actual  ");       // indicate type 

    display.setTextSize(3);

    display.setCursor(10, 30);       // clear last value

    display.print("       ");

    // update display

    display.setCursor(10, 30);

    display.print( (AttenValue + InsertionLoss), 1) ; 

  }

  else {

    display.setTextSize(1);        // show relative value

    display.setCursor(20, 15);

    display.print("Relative ");    // indicate type 

    display.setTextSize(3);

    display.setCursor(10, 30);

    display.print("       ");      // clear last value

    // update display

    display.setCursor(10, 30);

    display.print( AttenValue, 1);

  }

  // display "dB." 

  display.print( " ");

  display.setTextSize(2);

  display.setCursor(80, 38);

  display.print( " dB.");

  display.display();

Updated code is available at 

https://www.dropbox.com/sh/lwy52lqi0g0ms7g/AAChK1tqW8M4hmUUf_dutwP2a?dl=0