7 Segment Displays Overview

Introduction

The Great Cow BASIC 7 segment display methods make it easier for Great Cow BASIC programs to display numbers and letters on 7 segment LED displays.

The Great Cow BASIC methods support up to four digit 7 segment display devices, common anode/cathode and inversion of the port logic to support driving the device(s) via a transistor.

There are three ways that the 7 segment display routines can be set up.

Method Description

1

Connect the microcontroller to the 7 segment display (via suitable resistors) using any eight output bits.

Use DISP_SEG_x and DISP_SEL_x constants to specify the outpout ports and the select port(s) to be used.

2

Connect the microcontroller to the 7 segment display (via suitable resistors) using whole port (8 bits) of the microcontroller.

This implies the connections are consectutive in terms of the 8 output bits of the port.

Use the DISPLAYPORTn and DISPSELECTn constants to specify the whole port and the select port(s) to be used.

This method will generate the most efficient code.

3

Connect the microcontroller to the 7 segment display (via suitable resistors) using whole port (8 bits) of the microcontroller.

This implies the connections are consectutive in terms of the 8 output bits of the port.

Use the DISPLAYPORTn and DISP_SEL_n constants to specify the whole port and the select port(s) to be used.

The Great Cow BASIC methods assume the 7 segment display(s) is to be connected to a common parallel bus with a Common Cathode. See the sections Common Cathode and Common Anode for examples of using Great Cow BASIC code to control these different configurations

Shown below are the differing constants that must be set for the three connectivity options.

Index Method Description Constants Default Value

1

DISP_SEG_x & DISP_SEL_x

     
   

DISP_SEG_x

Specifies the output pin (output bit) used to control a specific segment of the 7 segment display.

There are seven constants that must be specified.

DISP_SEG_A through DISP_SEG_G. One must be set for each segment.

Typical commands are:

#define DISP_SEG_A portA.0

#define DISP_SEG_B portA.1

#define DISP_SEG_C portA.2

#define DISP_SEG_D portA.3

#define DISP_SEG_E portA.4

#define DISP_SEG_F portA.5

#define DISP_SEG_G portA.6

Must be specified to use this connectivity option.

   

DISP_SEG_DOT

Specifies the output pin (output bit) used to control the decimal point on the 7 segment display.

Typical commands are:

#define DISP_SEG_DOT portA.7

Optional.

   

DISP_SEL_x

Specifies the output pin (output bit) used to control a specific 7 segment display.

These constants are used to control the specific 7 segment display being addresses.

Typical commands are:

#define DISP_SEL_1 portA.0

#define DISP_SEL_2 portA.1

A valid output pin (output bit) must be specified. Must be specified to use this connectivity option.

2

DISPLAYPORTn & DISPSELECTn

     
   

DISPLAYPORTn

Specifies the output port used to control the 7 segment display.

Port.bit >> Segment

port.0 >> A

port.1 >> B

port.2 >> C

port.3 >> D

port.4 >> E

port.5 >> F

port.6 >> G

Can be DISPLAYPORTA and/or DISPLAYPORTB and/or DISPLAYPORTC and/or DISPLAYPORTD

Where DISPLAYPORTn can be A, B, C or D which corresponding to displays 1, 2, 3 and 4, respectively.

Must be specified to use this connectivity option.

   

DISPSELECTn

Specifies the output command used to select a specific 7 segment display addressed by DISPLAYPORT_n.

Used to control output pin (output bit) when several displays are multiplexed.

Typical commands are: #define DispSelectA Set portA.0 on

#define DispSelectB Set portA.1 on

Can be DISPSELECTA and/or DISPSELECTB and/or DISPSELECTC and/or DISPSELECTD

Must be specified to use this connectivity option.

   

DISPDESELECTn

An optional command to specify the output command used to deselect a specific 7 segment display addressed by DISPLAYPORT_n.

Used to control output pin (output bit) when several displays are multiplexed.

Typical commands are:

#define DispDeSelectA Set portA.0 off

#define DispDeSelectB Set portA.1 off

Can be DISPDESELECTA and/or DISPDESELECTB and/or DISPDESELECTC and/or DISPDESELECTD

3

DISPLAYPORTn & DISP_SEL_n

     
   

DISPLAYPORTn

Specifies the output port used to control the 7 segment display.

Port.bit >> Segment

port.0 >> A

port.1 >> B

port.2 >> C

port.3 >> D

port.4 >> E

port.5 >> F

port.6 >> G

Can be DISPLAYPORTA and/or DISPLAYPORTB and/or DISPLAYPORTC and/or DISPLAYPORTD

Where DISPLAYPORTn can be A, B, C or D which corresponding to displays 1, 2, 3 and 4, respectively.

Must be specified to use this connectivity option.

   

DISP_SEL_n

Specifies the output command used to select a specific 7 segment display addressed by DISPLAYPORTn.

Typical commands are:

#define DISP_SEL_1 portA.0

#define DISP_SEL_2 portA.1

Must be specified to use this connectivity option.

Can be specified as DISP_SEL_1 and/or DISP_SEL_2 and/or DISP_SEL_3 and/or DISP_SEL_4

Example 1:

 'A Common Cathode 7 Segment display  2 digit example

 #chip 16F886, 8

    'support for Common Anode
    '#define 7Seg_CommonAnode

    'support for pfet or pnp high side drivers
    '#define 7Seg_HighSide

' ----- Constants
	  ' You need to specify the port settings
	  ' by one of the following three methods
	  'The Directions of the ports are automaically set according to the defines
	'''METHOD 1  Define individual port pins for segments and selects
	  #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 '' available on some displays as dp or colon

	  #define DISP_SEL_1 PORTC.5
	  #define DISP_SEL_2 PORTC.4

	'''METHOD 2  Define DISPLAYPORTA (B,C,D) for up to 4 digit display segments
				''Define DISPSELECTA (B,C,D) for up to 4 digit display selects
	  '#define DISPLAYPORTA PORTB   ' same port name can be assigned
	  '#define DISPLAYPORTB PORTB

	  '#define DispSelectA Set portC.5 off
	  '#define DispSelectB Set portC.4 off
	  '#define DispDeSelectA Set portC.5 on
	  '#define DispDeSelectB Set portC.4 on

	'''METHOD 3  Define DISPLAYPORTA (B,C,D) for up to 4 digit display segments
				''Define port pins for the digit display  selects
	  '#define DISPLAYPORTA PORTB
	  '#define DISPLAYPORTB PORTB

	  '#define DISP_SEL_1 PORTC.5
	  '#define DISP_SEL_2 PORTC.4



		Dim Message As String
		Message = " HAPPY HOLIDAYS  "
		Do
		For Counter = 1 to len(Message)-1
			Repeat 50
				Displaychar 1, Message(Counter)
				wait 3 ms
				DisplayChar 2, Message(Counter+1)
				wait 3 ms

			  end Repeat


			Wait 100 ms
		Next
		Loop
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Also, see DisplayChar, DisplayValue