Manometer project continued.

[aajgss]

OK, I have the math to a point where it is calculating somewhere near the number I want.

I have connected the hardware. A MPXV4006 pressure sensor which is connected to a MCP3201 ADC which in turn goes via SPI to a 18F14K50 PIC.

Attached is the setup.

' Variables
SCK     VAR PORTB.6 'Clock pin
CS     VAR PORTC.1 'Chip Select Active low
SDI     VAR PORTB.4 'Data In pin
 
 COUNTS var word
 lbit var COUNTS.byte0
 hbit var COUNTS.byte1
'-------------------------------------------------------------------------------
Define LOADER_USED 1
INCLUDE "MODEDEFS.BAS"
DEFINE OSC 12
DEFINE SHIFT_PAUSEUS 10  'gives a 50KHZ clock pulse                                                       
TRISB.4 =1               ' set PortB 4 as an input
TRISB.6 =0               ' set PortB 6 as an output         
 
TRISC =%00000000                        
knots var long
knotsRem var long
HIGH CS
START:
 
LOW CS 
PAUSEUS 50 'delay after CS goes low for conversion to start. Probably not needed
SHIFTIN SDI,SCK,2,[counts\14]  ' using mode 2 for SPI
high cs 
 
'knots = ((SQR(counts*100))*1563)/10000
'knotsRem = (SQR(counts*100)*1563)//10000
'serout2  portb.7,396,[ #Knots,".",dec3 knotsRem,"  ",#counts,",","   Knots",13,10]
serout2  portb.7,396,[ #lbit,"   ",#hbit,13] ' Just send out ADC value to start
GOTO START:
END

I can see the data coming in on the scope. If I move the plunger of the syringe, I get the data changing, but always get a Zero when I send it out to the serial port.

I havent used the shiftin command before. It looks right so I'm not sure where I am going wrong.

Any help would be appreciated.

TIA
aajgss

[Ioannis]

If your data to see on terminal is in the counts variable, you have this line commented out.

Ioannis

[aajgss]

Thanks Ioannis,

I changed it to counts, Unfortunatly no difference, but at least if it was working I wouldn't have seen it anyway. Thanks for the tip.

I also Added

ANSELH.2 = 0

This then worked, however I must say when I read the datasheet for the 18F14K22 I interpret it that it should be digital so it wouldnt be necessary to add this statement so I am a bit confused. Maybe another 40 or 50 reads and it might sink in!!!

regards
aajgss

[aajgss]

I now have everything working and calculating air speed

I used "DEC1" to only print out to one decimal point.

Running the program gave some strange results. On occasion the count would increase, but the Knots value woud reduce.

By printing out all of the remainder, I could see what was going on.
eg for 2577 counts, the value would be 110.7 and for 2579 counts the value would be 110.1. The problem being in the true value

2577 counts is 110.457 and 110.501. The "DEC1" would give the digit either the 1 or 7 and not the 4 or the 5 as I expected (read hoped)

How can I get the first digit?

thanks
aajgss

[mackrackit]

What does your code look like now?

[aajgss]

Hi Dave,

Code is attached. Thanks for looking

Define LOADER_USED 1
INCLUDE "MODEDEFS.BAS"
DEFINE OSC 12
DEFINE SHIFT_PAUSEUS 10                                                       
TRISB.4 =1               ' set PortB 4 as an input
TRISB.6 =0               ' set PortB 6 as an output         
ANSELH.2 =0
DEFINE ADC_BITS 8
DEFINE ADC_CLOCK 3
DEFINE ADC_SAMPLEUS 50
ANSEL =%10000000      ' Enable ADC channel-AN2
ANSELH =%0000                         
OSCCON=%01100000                       
TRISA =%00001111                        ' Set ports A3-A2-A1-A0 as inputs
                       
TRISC =%01001000                        
knots var long
knotsRem var long
zero var word
zeroSw var portc.6
i var byte
avg var word
HIGH CS
START:
for i = 1 to 10 
LOW CS 
PAUSEUS 150 'delay after CS goes low for conversion to start. Probably not needed
SHIFTIN SDI,SCK,2,[counts\14]  ' using mode 2 for SPI
high cs 
avg = counts + avg
next
counts = avg/10
avg=0
if zeroSw then  zero = counts                               'Get value at zero pressure
if zeroSw then high portc.2
counts = counts -zero  'set zero point 
if counts >65000 then counts= 0                           'in case of underflow
knots = (((SQR(counts*10000))*65500)/301)/10000
knotsRem = ((SQR(counts*10000)*65500)/301)//10000
serout2  portb.7,396,[ #Knots,".",Dec1 knotsRem," Knots   ",#counts,"   ",#zero,10,13]
GOTO START:
END

Thanks
aajgss