PIC16F877 A/D Experiments with PicBasic

BASIC Stamp, Microchip PIC, 8051, and Remote Control Projects

PicBasic Experiments With The PIC16F877

This first application shows how to use the PIC16F877 Port A analog inputs. The analog values are displayed on the LCD. If you entered this page from another link, click HERE for the LCD connection schematic so you can follow along with these experiments.

Figure 1 shows the schematic used for this experiment. Port A.0, A.1 and A.3 are used in analog-input mode. The readings taken from each port-pin are then displayed on the LCD.

Figure 1: Potentiometer connections for A/D experiment.

Here is the PicBasic code:


' Picbasic Pro program to read pots on 16F877 ADC

' Define LCD pins
Define  LCD_DREG        PORTD
Define  LCD_DBIT        4
Define  LCD_RSREG       PORTE
Define  LCD_RSBIT       0
Define  LCD_EREG        PORTE
Define  LCD_EBIT        1
TRISA = %00001011
' Allocate variables
x       var     byte
y       var     byte
z       var     byte

        ADCON1 = 4              ' Set PortA 0, 1, 3 to A/D inputs

        Low PORTE.2             ' LCD R/W line low (W)
        Pause 100               ' Wait for LCD to start

        Goto    mainloop        ' Skip subroutines


' Subroutine to read a/d converter
getad:
        Pauseus 50              ' Wait for channel to setup

        ADCON0.2 = 1            ' Start conversion
        Pauseus 50              ' Wait for conversion

        Return

' Subroutine to get pot x value
getx:
        ADCON0 = $41            ' Set A/D to Fosc/8, Channel 0, On
        Gosub getad
        x = ADRESH
        Return

' Subroutine to get pot y value
gety:
        ADCON0 = $49            ' Set A/D to Fosc/8, Channel 1, On
        Gosub getad
        y = ADRESH
        Return

' Subroutine to get pot z value
getz:
        ADCON0 = $59            ' Set A/D to Fosc/8, Channel 3, On
        Gosub getad
        z = ADRESH
        Return


mainloop:
        Gosub   getx            ' Get x value
        Gosub   gety            ' Get y value
        Gosub   getz            ' Get z value

        Lcdout $fe, 1, "x=", #x, " y=", #y, " z=", #z ' Send to LCD
        Pause   100             ' Do it about 10 times a second

        Goto    mainloop        ' Do it forever

        End

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