A to D to A help

Im new at this so please be gentle. I'm using a pic185252 and a ltc1661 d to a.

The circuit needs to take a voltage reading from a flow sensor sample that

voltage by a set number of samples (16,32,64 etc.. this number will be chosen in

a varible with the inital flash of the mcu) take that voltage go to a 256 point

lookup table in the flash to convert this voltage reading to a flow rate number

this flow rate number will then be multiplied by a scalar (variable in inital flash)

this flow number will then be used with a 64point lookup table in the eeprom (64

ponts set with inital flash) to convert it back to a different voltage..

the first table will be 256 points from 0-6 volts

the second table will be 64 points with flow values from 0 to 388 kg/hr, 0 to 777

kg/hr, 0 to 1555 kg/hr, 0 to 2332 kg/hr, 0 to 3110, and 0 to 3888. the range will

be selected with a variable in the inital flash. the table will convert these flows

back to voltages.

all the tables will need interpolation.

My friend helped me write a simple code to just do a direct voltage conversion but i think I need to rework the whole thing for what i'm trying to do now..

here is the code for the first one

Code:

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' Uses 18F252 and 20MHz external clock.
' The lookup table contains 65 values, from 0 to 6V input.
' communicates with PC through serial port.
' Has an added 32 sample average on the input.



Define OSC 20  ' use 20 Mhz clock

Define  ADC_BITS    10
Define  ADC_CLOCK    3
Define  ADC_SAMPLEUS 24

' initial EEPROM values (output = input)
EEPROM [216,0,217,0,219,0,223,0,229,0,237,0,246,0,0,1,12,1,_
          22,1,30,1,42,1,55,1,69,1,86,1,104,1,_
          124,1,143,1,163,1,184,1,202,1,219,1,237,1,254,1,15,2,_
          32,2,49,2,66,2,82,2,98,2,114,2,130,2]       
EEPROM 128,[146,2,161,2,177,2,192,2,207,2,222,2,237,2,252,2,11,3,_
          26,3,40,3,55,3,70,3,84,3,99,3,113,3,_
          128,3,142,3,156,3,170,3,183,3,197,3,210,3,223,3,236,3,_
          249,3,255,3,255,3,255,3,255,3,255,3,255,3,0,4]
         
adval VAR WORD      ' analog input value
outputval VAR WORD  ' output value
tempval VAR WORD    ' temporary
tablehigh VAR WORD  ' high table value
tablelow VAR WORD  ' low table value
tempval2 VAR WORD  ' temporary #2
avgarray VAR WORD[32]' array for averaging input samples
countnum VAR byte  ' integer for counting sample array
arraysum VAR WORD  ' summing variable for average

TRISA = 255        ' portA => input
ADCON1 = %10000010  ' Set PORTA to analog and PORTE to digital

TRISB = %00000000 ' Port B set for output
HIGH PORTB.2      ' Serial D-A chip select off
countnum = 0
clearloop:          ' zero out array
if countnum != 32 then
    avgarray[countnum]=0
    countnum = countnum + 1
    goto clearloop
endif
countnum = 0
arraysum = 0

loop:  ' start of main loop
   
    Adcin 0, adval
    arraysum = arraysum - avgarray[countnum]  'subtract value at countnum
    avgarray[countnum] = adval                'store new value in array
    arraysum = arraysum + adval              'add to sum value
    adval = arraysum >> 5                    'divide by 32
    countnum = countnum + 1
    if countnum = 32 then
    countnum = 0
    endif
   
    tempval = adval >> 3    ' shift input for table lookup
    tempval2 = tempval & %1111111111111110 ' clear last bit for WORD lookup
   
    'get table high and low values
    READ tempval2+2,tablehigh.BYTE0
    READ tempval2+3,tablehigh.BYTE1
    READ tempval2,tablelow.BYTE0
    READ tempval2+1,tablelow.BYTE1
   
    'Table Interpolation
    tempval = adval & %0000000000001111 ' get interpolation value
    IF tablehigh >= tablelow THEN      ' get space between table values
    tempval2 = tablehigh - tablelow    '
    ELSE                                '
    tempval2 = tablelow - tablehigh    '
    ENDIF                              '
    tempval = tempval2 * tempval        'multiply high/low diff by interp value
    outputval = tempval >> 4            'divide by table spacing
   
    IF tablehigh >= tablelow THEN      ' offset table value by calculated
    outputval = outputval + tablelow    ' interpolation value
    ELSE                                '
    outputval = tablelow - outputval    '
    ENDIF                              '
   
    tempval = outputval << 2  ' shift output left 2 bits(LTC1661 DtoA)
    tempval = tempval + %1001000000000000  ' add control code(load DAC A)
    LOW PortB.2    ' Enable DtoA chip
    Shiftout PORTB.0,PORTB.1,1,[tempval\16] ' Serial output to DtoA conv
    High PORTB.2    ' Deselect DtoA chip
   
    goto loop      ' repeat main loop "forever"

End

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Awdgsx,

What is your question? What do you need help with?

Robert

well the first one is how do I store a table into the flash memory instead of the EEPROM

Use the WRITECODE and READCODE commands. These commands cannot be used in all the chips. Refer to the manual for more info.

Thank you!

See:
Making Program Code Space your playground...
http://www.picbasic.co.uk/forum/showthread.php?t=137

Thank you Melanie!

I would do something around some in the following
http://www.picbasic.co.uk/forum/showthread.php?t=1999&

So like this for my table..

Code:

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WRITECODE 16384 , 1011
WRITECODE 16385 , 2014
WRITECODE 16386 , 3014
WRITECODE 16386 , 4050

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