Help with A/D math!

[thronborg]

My first PIC program works!

Description
A pot connected to an A/D port gives 0-255
A little converting give an output of 1mS when pot CCW and 255 when pot is max CW.
Drives the Servo between 1-2mS
Show the Pot input on LCD line 1, 0-255.
Show the Pulse width in mS on LCD line 2, 1-2mS.

Se Drawing below.

'************************************************* ***************
'* Name : NimSer.BAS *
'* Date : 3/3/2011 *
'* Notes : Move Servo 1 to 2mS depend on POT value *
'* Show valu in mS on LCD display *
'* For standard servo settings 1-2mS set LOW_servo con 100 *
'* and HIGH_servo CON 200 *
'************************************************* ***************
'Define OSC and ADC
DEFINE OSC 4 ' Set internal Oschillator to 4Mhz
DEFINE ADC_BITS 8 ' Set number of bits in result
DEFINE ADC_CLOCK 2 ' Set clock source (3=rc)
DEFINE ADC_SAMPLEUS 50 ' Set sampling time in uS
' Define LCD pins
Define LCD_DREG PORTC 'LCD data port
Define LCD_DBIT 0 'LCD data starting bit 0 or 4
Define LCD_RSREG PORTC 'LCD register select port
Define LCD_RSBIT 4 'LCD register select bit
Define LCD_EREG PORTC 'LCD enable port
Define LCD_EBIT 5 'LCD enable bit


TRISA = %00001001 ' RA0 = A/D input
ADCON1.7 = 0 ' RA.1 = +Vref, Set PORTA analog and left justify result
PORTb.6 =0 ' Prepare RB0 for high-going pulseout

ANSEL = %00000100 ' Set PORTA.2 analog, rest digital
ANSELH = %00000000

' Variables
outpuls VAR WORD ' Variable for the calculated puls out in mS
POT_POS VAR BYTE ' Pot position CC=0, CCW=255
LOW_servo con 60 ' Min Servo pulse 60= 0.6mS 100=1mS
HIGH_servo CON 200 ' Max Span from LOW_servo to HIGH_servo
' Span 100 gives 100+100 = 200=2mS
Pause 500 ' Wait for LCD to start

MainLoop: ' The Loop start here!
ADCIN 0,POT_POS ' Read A/D channel 0 to variable SVO_POS
outpuls =LOW_servo + (POT_POS *HIGH_servo/255) 'Calculate the outpuls in mS
Lcdout $fe, 1, "POT_POS= ", #POT_POS ' Display POT Valu between 0-255 on line 1
LCDOut $fe,$C0, "Puls= ",DEC (outpuls/100),".", DEC2 outpuls,"mS"' Display pulswith in mS on line 2

PULSOUT portb.6 ,outpuls ' Move servo on pin
PAUSE 20 ' Constant 20mS pulses(low) between outpuls
GOTO MainLoop ' Forever
End

Pot to Servo and LCD.pdf

[Ioannis]

Nice you got it working. Also very nice graphics in your pdf file!

Ioannis

[thronborg]

Thank's Ioannis. There is a long way to go. But i start to understand what every body is talking about, Loook in the datasheet, 70% of the answer is there.

Continue the good work, I will try.

Ole

[Ioannis]

I see that you have the potential. From your first question to your complete working code there was an impressive progress.

By he way what you used for the graphics?

Ioannis

[thronborg]

Hey
No no i have not write everything by myself, i take some examples here and there and i got help here at the forum. So i am not so smart as it looks.

Actually i use a very old program, Freehand MX. Its still available at Adobes site. Why i use it? Because i have used it for 20 years and its in my fingertips. I made the symbol library myself, if you want it just let me know.

My development kit always go with me.
My MacBook Pro
Proteus
PicBasicPro
MikroC pro for PIC
PIC-kit 2
Programmer
Developer Board CP-Pic training, buyed in Bangkok for 60 euro. se picture.

Great to have everything from Mac and PC in the same Computer.

Ole

http://www.etteam.com/product/01B10.html

[MikeWinston]

Hi Dave,
I've used the DIV32 function alot for stuff like this. In your example I would do something
like this.
50" - 6" = 44"
44" / 1024(10bit) = 0.042968
convert this number to word constant in your program 42968
multiply a/d result by 42968
the very next line must be DIV32 statement (word var = DIV32 10000)
then add your 6" offset (+ 600)

example: (a/d result = 1023)
1023 * 42968 = 43956264 '(32bit result you can't access but DIV32 can)
res = DIV32 10000 '(res = 4395)
res = res + 600 '(res = 4995 hundreth inches or 49.95 inches)

Mike