ADC in 12F683; puzzled

[Acetronics2]

Hi, Mike

How do you want us to give you any idea ???

PLEASE ...

Your program With the Config Header ... as always !!!

Alain

[mikebike]

Your program With the Config Header ... as always !!!

Alain

Right, of cource...

 
'Define ADCIN parameters
ANSEL = %00000011 'GP0 = AN0, GP1 = AN1
 
DEFINE ADC_BITS 10 'Set number of bits in result
DEFINE ADC_CLOCK 3 'Set clock source
DEFINE ADC_SAMPLEUS 50 'Set sampling time in us
 
time1 VAR WORD 'First time in seconds
time2 VAR WORD 'Second time in seconds
time3 VAR WORD 'Third time in seconds
involt1 VAR word 'Value for ADC0 (temp)
involt2 VAR word 'Value for ADC1 (adjust)
ut4 var bit 'Status for LED 4
ut5 var bit 'Status for LED 5
trip1 var word 
trip1 = 13300 'Default value
trip2 var word 
trip2 = 13300 'Default value
 
TRISIO = %11001011 'Defining PORT
GPIO = %00111000 'Turn off all LEDs
time1 = 0 'Zero time 1
time2 = 0 'Zero time 2
time3 = 0 'Zero time 3
ut4 = 1 'LED 4 = off (inversed)
ut5 = 1 'LED 5 = off (inversed)
 
loop1: 
ADCIN 0, involt1 'Read channel 0 to involt1
ADCIN 1, involt2 'Read channel 0 to involt2
pause 100 'Wait 100 ms
IF involt1 >= trip1 THEN 
GPIO.4 = 0 'Turn on LED4
else
GPIO.4 = 1 'Turn off LED4
endif
IF involt2 >= trip2 THEN 
GPIO.5 = 0 'Turn on LED5 
else
GPIO.5 = 1 'Turn off LED5
endif 
goto loop1 'Go back to loop1
END

trip1 = 13300 gives exactly 1V trip level. I don't mind having this kind of resolution, but it doesn't seem realistic.

[Acetronics2]

Right, of cource...

trip1 = 13300 gives exactly 1V trip level. I don't mind having this kind of resolution, but it doesn't seem realistic.

Missing :

- Deactivate comparators
- ADC result right justified

Alain

[mikebike]

Missing :

- Deactivate comparators

Is this specific for 10 bit ADC, or should it be there for 8 bit conversion as well?
And how? -CMON0 something?

Missing :
- ADC result right justified
Alain

Hm, the example programs that I have (for 16F877A) do not have such an instruction, does that PIC not need it?

ADCON0.7 = 1 seems to have have cured the problem, thanks guys.

[Acetronics2]

Is this specific for 10 bit ADC, or should it be there for 8 bit conversion as well?
And how? -CMON0 something?

have a look to datasheet ... Comparator section !!!

Hm, the example programs that I have (for 16F877A) do not have such an instruction, does that PIC not need it?

some pins share the comparator and ADC functions ... you HAVE to verify which function is deactivated and which is to activate. ( one at a time ... )

Depends on the chip used - and the ports used ...

ADCON0.7 = 1 seems to have have cured the problem, thanks guys.

Full config done = NO suprise ...

sometimes, the pic defaults @ reset are the ones you want ... sometimes not. so you have to verify everything with the pic Datasheet !!!

[mikebike]

have a look to datasheet ... Comparator section !!!

Done that, but didn't understand it (new to this stuff).

CMCON0 = %00000000

seems to be accepted by PBP and the chip (still) works.

[Acetronics2]

Done that, but didn't understand it (new to this stuff).

CMCON0 = %00000000

seems to be accepted by PBP and the chip (still) works.

Boooooooooooooo .... the chip is really gentle with you ...

look a bit closer at the drawings and the corresponding config @ $8 p 53 ...

Alain

[mikebike]

sometimes, the pic defaults @ reset are the ones you want ... sometimes not. so you have to verify everything with the pic Datasheet !!!

Yes, I have had some interesting output signals on outputs that were not specified in the program!

[cncmachineguy]

Just guessing with your code, It looks like your result is left justified (or right) but in any event, you appear to be reading the the 2 LSB as bit 6,7 of your answer. since the 10 bit result is a word, you seem to have result high as valid 8 bits. but your result low is ddxxxxxx. So your LSB is really = dec128 and not 1!

How do i guess this? if you right shift your 13300 6 times, you get ~207. Assuming you are testing 0-5V you expect 1024/5=204 per volt. Pretty close.

If you need help understanding or fixing this, post code!

Sorry, we posted together