In SX Microcontrollers, SX/B Compiler and SX-Key Tool, Sawmiller wrote:

how much range should analogin be good over ?
i'm creating a voltmeter, using a sx28 and a HC4led 

and have a program, but i keep having to change the multipilyer values to get the number on the HC4led right with my regular voltmeter.

im looking a a 0 -35 volt range but at 11 volts i need 164 as a multiplier, and at 35 volts i need 138..

 

[u][b]i'm really not to sure what bean means by impedance of the voltage to the resistor :confused:  [/b][/u]

currently using a voltage divider 10k on one side then 60 k on the other then that goes straight to the sensor.

see comments for further stuff

if anyone can explain why this is happening, please enlighten me

 


' -------------------------------------------------------------------------
' Device Settings
' -------------------------------------------------------------------------

DEVICE SX28,OSC4MHZ,TURBO,STACKX,OPTIONX
FREQ 4_000_000

' -------------------------------------------------------------------------
' IO Pins
' -------------------------------------------------------------------------

Clk       VAR RA.0
Dat       VAR RA.1
InPin   PIN RC.0 INPUT CMOS
OutPin   PIN RC.1 OUTPUT
 
' -------------------------------------------------------------------------
' Constants
' -------------------------------------------------------------------------

MINUS      CON 11 ' Used for DisplayValue parameters
BLANK      CON 10 ' Used for DisplayValue parameters
volt_scale  CON 138      'used to give a range between 0- 35 volts max expected is 32
' -------------------------------------------------------------------------
' Variables
' -------------------------------------------------------------------------

value     VAR Byte (4)
segments  VAR Byte (4)
cnt       VAR Byte
temp1     VAR Byte
counter   VAR Byte 
Volt      VAR byte
Voltage  VAR Word

' =========================================================================
  PROGRAM Start
' =========================================================================


' -------------------------------------------------------------------------
' Subroutine Declarations
' -------------------------------------------------------------------------

DisplayValue    SUB 4
UpdateValue     SUB
DisplaySegments SUB 4
LEDOut          SUB 1
putz      SUB
fancy_start   SUB

' -------------------------------------------------------------------------
' Program Code
' -------------------------------------------------------------------------

Start:
  HIGH Clk

Main:
'fancy_start


again:
value(3) = 0
value(2) = 0
value(1) = 0
value(0) = 0


ANALOGIN InPin, OutPin, Volt,5
Voltage = Volt

if Voltage = 0 goto display

Voltage = Voltage * volt_scale   ' mutiply to get right numbers

Voltage = Voltage / 10      ' knock off last  digit  ( easier to multiply by 164, than 16.4 )

if voltage = 0 goto display
Voltage = Voltage / 10
                 ' hundredths
value(3) = __REMAINDER 

if voltage = 0 goto display
Voltage = Voltage / 10
                    ' tenth's
value(2) = __REMAINDER

if voltage = 0 goto display
Voltage = Voltage / 10
                     ' ones
value(1) = __REMAINDER

if voltage = 0 goto display
Voltage = Voltage / 10
                     ' tens
value(0) = __REMAINDER

display:

DisplayValue value(0),value(1),value(2), value(3)
pause 100

  GOTO again

' -------------------------------------------------------------------------
' Subroutine Code
' -------------------------------------------------------------------------

 

Fancy_start:

for counter = 1 to 10
  

   FOR cnt = 0 to 3

     segments(cnt) = 4
    
    gosub putz
   next

  segments(3) = 8
  gosub putz


  segments(3) = 16
  gosub putz


  FOR cnt = 3 to 0 step -1

     segments(cnt) = 32
     gosub putz
 
  next


  segments(0) = 64
  gosub putz

  segments(0) = 2
  gosub putz


 next

return

DisplayValue:
  PUT value,__PARAM1,__PARAM2,__PARAM3,__PARAM4

UpdateValue:
  FOR cnt = 0 to 3
    temp1 = value(cnt)
    READ DigitSegs+temp1,segments(cnt)
  NEXT
  GOTO DisplayArray

DisplaySegments:
  PUT segments,__PARAM1,__PARAM2,__PARAM3,__PARAM4

DisplayArray:
  HIGH Clk
  LEDOut segments(3)
  LEDOut segments(2)
  LEDOut segments(1)
  LEDOut segments(0)
  RETURN  


LEDOut:
  temp1 = __PARAM1
  SHIFTOUT Dat, Clk, MSBFIRST, temp1
  RETURN

putz:

  HIGH Clk
  LEDOut segments(3)
  LEDOut segments(2)
  LEDOut segments(1)
  LEDOut segments(0)

    pause 100 

   segments(3) = 0
   segments(2) = 0
   segments(1) = 0
   segments(0) = 0
return

' -------------------------------------------------------------------------
' Data
' -------------------------------------------------------------------------

DigitSegs:
  DATA 126,24,109,61,27,55,115,28,127,31,0,1

---------- End of Message ----------


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