awdgsx
- 22nd June 2011, 21:23
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
' 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,_
128,3,142,3,156,3,170,3,183,3,197,3,210,3,223,3,23 6,3,_
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
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
' 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,_
128,3,142,3,156,3,170,3,183,3,197,3,210,3,223,3,23 6,3,_
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