A/D conversion with PIC18F67J50

[Darrel Taylor]

I believe it's the ADCON0 = %00000000 'turn off adc

You probably get a reading the first loop through.
But for all loops after that, the A/D module is turned off.
<br>

[ScaleRobotics]

Thanks Darrel,

I commented out my ADCON0 = %00000000 and put the loop back in, and confirmed my loop is looping. My result seems to be stuck at 24543, 40910 or 8142 each time I reset. Basically giving me random numbers as best I can tell. But despite the loop looping, the numbers do not change, until I remove power from the unit, then apply power again.

DEFINE OSC 48

include "modedefs.bas"
include "LCD_3310.pbp"

TRISD = 0
PORTD.0 = 1   'turn on g sensor
PORTD.1 = 0   'select scale for g sensor
PORTD.2 = 0   'select scale for g sensor


TRISA = %00000111   'set porta.0, 1, and 2 as inputs
TRISB = 0
CM1CON = 7
CM2CON = 7
TRISC = 0
TRISE = 0
ADCON0 = %00000001      'turn on adc
ADCON1 = %00000010      'fosc/32 ?? 
'am I translating c language ADCON1=0x10 above correctly?

resx var word
x var word
y var word
z var word
adval var word

x=0
y=0
z=0
adval = 0

PORTD.0 = 1   'turn on g sensor (again)
'*************************************************
@ bsf WDTCON,ADSHR   ;set shared address SFR with WTCON<4> - is this right?
ADCON0 = %11111110  ' channel with a 0 is analog input, all others digital
@ bcf WDTCON,ADSHR
ADCON1 = %10111110  'right justified, AD=20AD, A/D clock=fosc/64
ADCON0.0 = 1        'turn on adc

ADCON0.2 = 0        'channel select bit CHS0(should already be a 0)
ADCON0.3 = 0        'Channel select bit CHS1(should already be a 0)


start:
    Pause 500       ' Wait .5 second
loop: 		ADCON0.1 = 1					'Start Conversion
adval = 0                                   'clear result word
notdone:	pause 5
	if ADCON0.1 = 1 Then notdone	'wait for low on bit-2 of ADCON0, conversion finished

	adval.highbyte = ADRESH			'move HIGH byte of result to adval
	adval.lowbyte = ADRESL			'move LOW byte of result to adval
            
        'ADCON0 = %00000000              'turn off adc
	    	
        'Lcdout $fe, 1   				'Clear screen
        'Lcdout "Value: ", DEC adval	'Display the decimal value  
            x = x +1                        'test to see if loop is working
@ PrintStr 0,0, "Z= "                       ;display on Nokia 3310
@ PrintVar 24,0, _adval                     ;display result on 3310
@ PrintVar 0,1, _x                          ;show if loop is looping
        Pause 100       				'Wait .1 second

       	Goto loop       				'Do it forever
End

[ScaleRobotics]

Whoops,

I noticed that it was going to my include file, then popping up at start: which missed all my settings to the ADCON0 etc.

Sometimes I have to say it out loud (to everyone) to figure it out, with the help of some experts. I won't tell anyone how many days I was trying..........

Thanks,

Walter

[mister_e]

You conversion clock seems a bit high @48MHz operation, and your first example in C used ANCON0, not yours.... yet...

While it's not a problem for now, one day you may need to disable some analog feature on this PIC... however, seems ANCON0 and ANCON1 are not included in PBP 2.50c, so I guess the following would be handy one day or another.

        '
        '       Configure ADC
        '       =============
        ANCON0  VAR BYTE EXT    ' not included in PBP2.50c
        ANCON1  VAR BYTE EXT    ' not included in PBP2.50c
        
        ANCON0 = %10011110
               '  -xx------ Not Implemented
               '  1--1111-- AN7, & AN<4:1> = Digital
               '  -------0- AN0 = Analog
               
        ANCON1 = %11111111
               '  11111111- AN<15:10> = Digital
                                     
        ADCON0 = %00000001
               '  0-------- VCFG1, Vref- 0 = AVss (1=AN2)
               '  -0------- VCFG2, Vref+ 0 = AVdd (1=AN3) 
               '  --0000--- CHS<3:0>, Channel select -- 0
               '  ------0-- Go/Done, don't care for now
               '  -------1- ADON, Enable ADC
                  
        ADCON1 = %10000111
               '  1-------- ADFM, Right justified result
               '  -0------- ADCAL, Normal A/D converter operation
               '  --000---- ACQT<2:0>, A/D Aquisition time = 0 Tad
               '  -----111- ADCS<2:0>, A/D conversion clock = FRC
                
        '
        '       Hardware Aliases
        '       ================
        GoDone      var ADCON0.1 ' StartConversion = 1, Conversion done = 0
        
        '
        '       Software Variables
        '       ==================
@ADVal = ADRESL
        ADVal       VAR WORD EXT
        
Start:
        pauseus 10  ' Acquisition time        
        GoDone = 1
        While GoDone : Wend
        LCDOUT $FE, 1, "Value: ", DEC ADVal
        PAUSE 250
        GOTO START

EDIT: for some odd reason, ANCON0 & ANCON1 are commented in PIC18EXT.BAS, i'd sent an e-mail to Melabs, obviously they must have a reason for that.

[ScaleRobotics]

Thanks mister_e ! I have flipped to page 299 to 302 so many times but never noticed the "D" to "N" change. Doh!

Do you think it is edited out because it is a shared address, only distinguished by the address share bit ADSHR in the WDTCON register?

Currently I have to:
@ bsf WDTCON,ADSHR 'flag address share bit
ADCON0 = %11111000 ' channels with a 0 is analog input, all others digital
@ bcf WDTCON,ADSHR
(or should I say I think? I have to....)

to set the aNcon0 register

(Despite all my mistakes, I am now getting valid conversion results, as of post 4)

[mister_e]

Holly crap, yeah, that make sense indeed. Yet another stupidity from Microchip

So my example will need some changes...

        '
        '       Configure ADC
        '       =============
        ANCON0  VAR BYTE EXT    ' not included in PBP2.50c
        ANCON1  VAR BYTE EXT    ' not included in PBP2.50c
        
        WDTCON.4 = 1    ' Switch to Alternate SFR
        ANCON0 = %10011110
               '  -xx------ Not Implemented
               '  1--1111-- AN7, & AN<4:1> = Digital
               '  -------0- AN0 = Analog
               
        ANCON1 = %11111111
               '  11111111- AN<15:10> = Digital
                                     
        WDTCON.4 = 0    ' Back to Default SFR

or

        '
        '       Configure ADC
        '       =============
        WDTCON.4 = 1    ' Switch to Alternate SFR
        
        ADCON1 = %10011110  ' alternate ANCON0
               '  -xx------ Not Implemented
               '  1--1111-- AN7, & AN<4:1> = Digital
               '  -------0- AN0 = Analog
               
        ADCON0 = %11111111  ' alternate ANCON1 
               '  11111111- AN<15:10> = Digital
                                     
        WDTCON.4 = 0    ' Back to Default SFR

By far, i prefer the first, easier to read

However, yours work.. keep it like that. If it's not broken, don't fix it!

[mister_e]

Side note... there's no real need to redefine ANCON1, ANCON0 as i did if you use ANCON1_ALT, ANCON0_ALT within your code. Those two are defined in PIC18EXT.BAS.

Having _ALT written at the right of the register name, may remember you to set/clear WDTCON.4 bit? Maybe

[ScaleRobotics]

Side note... there's no real need to redefine ANCON1, ANCON0 as i did if you use ANCON1_ALT, ANCON0_ALT within your code. Those two are defined in PIC18EXT.BAS.

Having _ALT written at the right of the register name, may remember you to set/clear WDTCON.4 bit? Maybe

Sweet! I did not see that either. May be time for glasses. And a lot cleaner than the way I was doing it, and I like the way you wrote the registry bits in the code. That would have kept me from having to divert my attention to and from tfm a lot!

Thanks for all the help.

Walter