GCBASIC documentation
7 Segment Displays - Legacy

Syntax:

    DisplayValue (display, data, dot)

Command Availability:

Available on all microcontrollers.

Explanation:

This command will display the given value on a seven segment LED display.

display is the number of the display to use. Up to 4 digits.

data is the value between 0 and F to be shown.

dot is an optional parameter. When it is 1 then the decimal point for that digit is turned on.

The command also support HEX characters in the range between 0x00 and 0x0F (0 to 15). See example two below for usage.

Example 1:

    'This program will count from 0 to 99 on two LED displays
    #chip 16F819, 8

  'See 7 Segment Display Overview for alternate ways of defining Ports
    #define DISP_SEG_A PORTB.0
    #define DISP_SEG_B PORTB.1
    #define DISP_SEG_C PORTB.2
    #define DISP_SEG_D PORTB.3
    #define DISP_SEG_E PORTB.4
    #define DISP_SEG_F PORTB.5
    #define DISP_SEG_G PORTB.6
  '#define DISP_SEG_DOT PORTB.7 ' Optional DP

    #define DISP_SEL_1 PORTA.0
    #define DISP_SEL_2 PORTA.1

    Do
        For Counter = 0 To 99

            'Get the 2 digits
            Number = Counter
            Num1 = 0
            If Number >= 10 Then
                Num1 = Number / 10
                'SysCalcTempX stores remainder after division
                Number = SysCalcTempX
            End If
            Num2 = Number

            'Show the digits
            'Each DisplayValue will erase the other (multiplexing)
            'So they must be called often enough that the flickering
            'cannot be seen.
            Repeat 500
                DisplayValue 1, Num1          ' <<< the DisplayValue instruction
                Wait 1 ms
                DisplayValue 2, Num2
                Wait 1 ms
            End Repeat
        Next
    Loop

Key line: DisplayValue 1, Num1 — writes Num1 to digit 1; because only one digit can be lit at a time on a multiplexed display, this call must be repeated fast enough (inside the Repeat 500 loop) that the eye perceives both digits as lit simultaneously.

Example 2:

    'This program will count from 0 to 0xff on two LED displays
    #chip 16F819, 8

    #define DISP_SEG_A PORTB.0
    #define DISP_SEG_B PORTB.1
    #define DISP_SEG_C PORTB.2
    #define DISP_SEG_D PORTB.3
    #define DISP_SEG_E PORTB.4
    #define DISP_SEG_F PORTB.5
    #define DISP_SEG_G PORTB.6

    #define DISP_SEL_1 PORTA.0
    #define DISP_SEL_2 PORTA.1
    #define DISP_SEL_4 PORTA.2
    #define DISP_SEL_3 PORTA.3

    Do
        For Counter = 0 To 0xff

            'Get the 2 digits
            Number = Counter
            Num1 = 0
            If Number >= 0x10 Then
                Num1 = Number / 0x10
                'SysCalcTempX stores remainder after division
                Number = SysCalcTempX
            End If
            Num2 = Number

            'Show the digits
            'Each DisplayValue will erase the other (multiplexing)
            'So they must be called often enough that the flickering
            'cannot be seen.
            Repeat 500
                DisplayValue 1, Num1          ' <<< DisplayValue with a hex digit (0-15)
                Wait 1 ms
                DisplayValue 2, Num2
                Wait 1 ms
            End Repeat
        Next
    Loop

Key line: DisplayValue 1, Num1 — here Num1 can range from 0 to 15, so DisplayValue shows the hex digits A through F as well as the decimal digits 0 through 9.

See Also: