Displaying Variables in NXC

[fuzzball27]

I need to know how to display variables on the NXT. It would be very helpful for future projects. For example, displaying the compass heading on one robot to a remote would be handy. It seems simple enough to display a variable's value but binary programming is sensitive

[mattallen37]

Use something like this.

Code: Select all

int heading;
task main()
{
  SetSensorLowspeed(S1);
  while (true)
  {
    heading=SensorHTCompass(S1);
    Wait (50);
    ClearScreen();
    NumOut(0,LCD_LINE1,heading);
  }
}

[gusjansson]

I usually avoid using ClearScreen since it can cause screen flicker. Instead I pair a TextOut with the NumOut. I use the TextOut to first display a caption as well as a bunch of spaces that will overwrite the previous value and then I display the new value offset by the length of the caption. For example, to display the Compass, I do this:

Code: Select all

//=====================================================================
// HiTechnic Compass Viewer

#define COMPASS S1

task main()
{
  int heading;
  
  SetSensorLowspeed(COMPASS);
  Wait(100);

  while(true) {
    heading = SensorHTCompass(COMPASS);

    TextOut(0, LCD_LINE4, "Compass:    ");
    NumOut(8*6, LCD_LINE4, heading);

    Wait(50);
  }
}

The 8*6 for the x position of the NumOut is the column*pixel width of a character. Since "Compass:" is 8 characters, 8*6 will put the number just right of the ':'.

[mattallen37]

I use a Wait(); to stop flicker. I suppose either way would work for this case.

[afanofosc]

The difference is ClearScreen erases the entire screen which takes longer than redrawing/erasing a single line. There is a new API function called ClearLine which you can use to only erase the specified line. I really like Gus's code, though.

The OP may have been talking about sending a variable's value to another device, though. For that I would consider using SendRemoteNumber. This uses the MessageWrite direct command and adheres to the message format used by the NXT-G message block.

John Hansen

[HaWe]

I need to know how to display variables on the NXT.

for displaying 3 values in 1 line with addional formating and adjustion of decimals I would suggest to use this simple macro.

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#define printf3( _x, _y, _format1, _format2, _format3, _value1, _value2, _value3) { \
  string sval1 = FormatNum(_format1, _value1); \
  string sval2 = FormatNum(_format2, _value2); \
  string sval3 = FormatNum(_format3, _value3); \
  string s =sval1+sval2+sval3; \
  TextOut(_x, _y, s); \
}

it's working somewhat like the original printf command (ANSI C stdio) but uses single format strings for every single value.
Blanks are inserted automatically.
the format strings may use integer format like "%2d" or fp format like "%4.1f"
use e.g.:

Code: Select all

#define printf3( _x, _y, _format1, _format2, _format3, _value1, _value2, _value3) { \
  string sval1 = FormatNum(_format1, _value1); \
  string sval2 = FormatNum(_format2, _value2); \
  string sval3 = FormatNum(_format3, _value3); \
  string s =sval1+sval2+sval3; \
  TextOut(_x, _y, s); \
}

task main(){
  int number=1;
  int length=23;
  float heading=45.6;
  printf3(0,56, "n=%1d", " L=%2d", " H=%4.1f", number,length,heading);
  while (true);
}

I assume if you extract the formatted value string (string s=sval1+sval2+sval3 of the macro) you might pass it to a BT send string function
HTH!