' Analog to Digital Conversion (ADC) routine for the DARC Board
' uses the ATMega8535 chip

' author: kerwin lumpkins
' this file calls an init_adc sub that initializes the adc module
' then it runs a loop that gets the adc value on channel 7 (pin A7)
' every 1/2 second (500 ms)

' put in the cal value for your part here (marked on the 8535 case
' most are hex 9F, some 91's and some in between
Osccal = &H9f
$regfile = "m8535.dat"


Declare Sub Init_adc
Declare Function Get_darc_adc(byval Channel As Byte) As Integer

Dim Adc_value As Integer
Dim Channel As Byte

Call Init_adc

Do
 Channel = 7
 Print "getting the adc"
 Adc_value = Get_darc_adc(channel)
 Print "Channel " ; Channel ; " value " ; Adc_value
 Print " "
 Waitms 500

Loop

Sub Init_adc
   ' set for AVCC reference voltage,Right justified,channel 0
   Admux = &H40

   'set ad status and control register for conversion disabled, conversion
   'not started,auto trigger disabled,interrupts disabled,and divide
   'by 64 prescaler
   Adcsra = &H06

End Sub Init_adc

Function Get_darc_adc(byval Channel As Byte) As Integer
   Dim Flag As Byte
   Dim Adcnotdone As Bit


   'init the admux for channel 0
   Admux = Admux And &HE0
   Admux = Admux + Channel

   'enable the adc
   Adcsra = &H86
   'start the conversion
   Adcsra = &HC6

   Adcnotdone = 1

   While Adcnotdone = 1
     Flag = Adcsra And &H40

     'wait until the adc interrupt flag is set
     If Flag = 0 Then Adcnotdone = 0
   Wend

   Dim Adcvalh As Integer
   Dim Adcvall As Integer
   Dim Adcval As Integer
   Adcvalh = 0
   Adcvall = 0
   Adcval = 0

   'get the 2 adc hi and lo bytes and combine into one integer value
   Adcvall = Adcl
   Adcvalh = Adch
   Shift Adcvalh , Left , 8
   Adcval = Adcvalh + Adcvall
   'Print "adcvalh:" ; Adcvalh ; " adcvall: " ; Adcvall ; "   adcval = " ; Adcval


   'disable conversion
   Adcsra = &H06

   Get_darc_adc = Adcval

End Function Get_darc_adc(byval Channel As Byte)