A/D converter PIC16F1827

[dovegroup]

i use this code but is not working




DEFINE ADC_BITS 10
DEFINE ADC_SAMPLEUS 50
'DEFINE ADC_CLOCK 3

ADCON0 = %00000001
ADCON1 = %01100011
ANSELA = %00000111
TRISA = %00000111

How to enable three channels (AN0,AN1,AN2) A/D converter PIC16F1827
any help please

[HenrikOlsson]

You've selected the FVR as reference for the ADC but I see no code that configures the FVR (it's disabled on POR).
That's how far I got with what's shown.

/Henrik.

[mpgmike]

ADCON1 = %01100011

For your ADC Clock to = 3, ADCON1 must be %0011....

You have the ADC Module looking at the FVR for a VREF+ (bits <2-0> of ADCON1). Nowhere in your listing do you mention setting up the FVRCON register so your ADC has its positive reference turned on. You might want to change ADCON1 to %00110000 and use Vdd for your VREF+.

You can use the ADCIN command, ADCIN 0, VAR and PBP will automatically adjust ADCON0 to AN0 for you, or you can work it manually:

ADCON0 = %00000011
DO
LOOP WHILE ADCON0.1 = 1. ;The GO bit
VAR = ADRESH

This gives you an 8-bit ADC value. For AN1, ADCON0 = %00000111, for AN2, ADCON0 = %00001011, and so forth.

[dovegroup]

mpgmike Thank you very much
Can you tell me how I will get a 10-bit price in the baty variable

my programm

baty var word

arxh:

ADCON0 = %00000011
DO
LOOP WHILE ADCON0.1 = 1
adcin 0,baty

if baty > 1050 then
gosub OK
endif

if baty < 1000 then
gosub noOK
endif

goto arxh

[Ioannis]

Look from page 142 and after the details of the AD converter. It always makes a 10 bit conversion. It is up to you if you want 8 or 10 bits result.

Anyway, having ADFM=1, the result is Right justified and stored in the ADRESH, ADRESL.

So get your result in the baty variable as:

baty.HIGHBYTE=ADRESH
baty.LOWBYTE=ADRESL

or

baty.BYTE1=ADRESH
baty.BYTE0=ADRESL

In any case for the variable handling (e.g. baty.BYTE1, etc) look at the PICBASIC reference manual.

Ioannis

[HenrikOlsson]

You don't have to first do a "manual conversion" (via the GO/DONE bit) and then do a ADCIN (which basically does the same thing for you).
If you're going to use ADCIN then add a DEFINE ADC_BITS 10. If you're going to use the "manual method" just do what Ioannis showed and get rid of the ADCIN command.

And once you DO have your 10-bit resuly this won't work because baty will never be >1050 since the maximum result returned by the 10 bit ADC is 1023:


if baty > 1050 then
gosub OK
endif


/Henrik.

[mpgmike]

There are some 12-bit ADC Modules in a few of the PICs if you want better resolution. Referencing the ADMF = 1, that would be ADCON1.7 = 1. Let us know how you make out.

[dovegroup]

Thank you all for the help. Excuse me .I am a novice to PICBASIC

[Ioannis]

That's what we are here for. Don't worry being novice. We all are, one way or another!

Henrik caught the over 1023 point that I missed. Be careful on this as the 10 bit might be not enough for what your are after.

But you can always scale the measurements. Tell us more to help.

Ioannis