Need help with 16f819 10 bit ADC

Hi

I'm new to forums and pic basic so please forgive if Iv'e missed somthing obvious.

I have built a battery charger, and I am using the 8 bit ADC on the 16f819 to measure the batt voltage and detect when it is fully charged.
The resolution for 8 bits was not quite good enough for my requirements so I want to use it in the 10 bit format.

My circuit and program works when using 8 bit, but when I try to use 10 bit, nothing happens.

I have a simple test circuit with LED's on the output of port b, and I can get the LED's to light, as a bar graph, in approx 10 mV increments.

Using the same test circuit and the code below for 10 bits, the leds are coming on as shown

RB0- on = 0V
RB1- on = 1.26V
RB2- on = 2.52V
RB3- on = 3.78V
RB4- dosn't come on.

Iv'e looked at the data sheet and lots of examples of 10 bit code, but can't see anything wrong with my program. I was hopeing for a resolution of about 5 mV.
I would be very gratefull if sombody could help.

Test program


DEFINE adc_bits 10
DEFINE adc_clock 3
DEFINE adc_sampleus 50

adval VAR WORD

portb=%00000000
trisb=%00000000

trisa=%11111111

adcon1=%100000010

loop:
ADCIN 2, adval

ledtst1:
IF adval > 0 THEN tst2
portb = %00000001
GOTO cont

tst2:
IF adval > 1 THEN tst3
portb = %00000011
GOTO cont

tst3:
IF adval > 2 THEN tst4
portb = %00000111
GOTO cont

tst4:
IF adval > 3 THEN tst5
portb = %00001111
GOTO cont

tst5:
portb = %00011111

cont:
PAUSE 100
GOTO loop
END

You have nine bits in this line.
adcon1=%100000010
That's probably the reason for the strange behaviour.

Sorry! thats a typing error in my post, actual code is correct.
It seems so simple I can't understand why it dosen't work.

Don't you need to change your command to ADCIN 4, adval to get AN4?

I personally have been using Melanies direct method reading analog values that can be seen in this thread

http://www.picbasic.co.uk/forum/show...ghlight=adcon0

Its pretty straight forward and I can understand what is going on.

Defines should be in uppercase.

DEFINE ADC_BITS 10
DEFINE ADC_CLOCK 3
DEFINE ADC_SAMPLEUS 50

Thanks modifyit, I'll try this when I get back to work on Monday and let you know how I get on.

Ingvar, I didn't think these were case sensitive, it worked OK lower case for 8 bit ADC but I will also try this on Monday.

Thanks both.

Your defines didn't do anything atall since they were the default values.

So if they are default values Then shouldn't the prog work?
The rest of the code works when set up for 8 Bits, can't see what else is wrong, confused!.

BG

It worked before you changed it to 10 bits. 8 bits is default. That's why it worked even though you wrote the defines in lowercase.

OK ingvar, see what your saying, will try as soon as I get the time,
(work gets in the way of projects)

Thanks

BG

ingvar, just changed defaults to upper case, program now works fine.
Just knew it had to be somthing stupid I had done.
Thanks for your help and patience.

BG