Again ADC with 12F675 ...

[fratello]

Hi !
I wote this code for 12F675:

@ __config _XT_OSC & _WDT_OFF & _PWRTE_ON & _MCLRE_ON & _BODEN_OFF & _CP_ON 

DEFINE OSC  4
DEFINE ADC_BITS 10
DEFINE ADC_CLOCK 3
DEFINE ADC_SAMPLEUS 50

CMCON = 7
OPTION_REG  = %10000110
TRISIO      = %00001100	  		
GPIO        = %00000001
ANSEL       = %00010100   
ADCON0      = %10001001

In ISIS I have multiple errors ... what did I do wrong ?

[HenrikOlsson]

Hi,
Is that really ALL of the code?

When you select an analog input which you want to convert the sample and hold circuit for the ADC needs to charge the S/H capacitor. It takes a certain amount of time (called acquisition time) for this capacitor to charge up. When the the A to D conversion starts the capacitor is disconnected from the input. If the A to D conversion is started before the acquisition time has expired the conversion result will not be correct.

I'm not sure if perhaps ISIS can, based on the simulation, figure out that the acquisition time isn't long enough. I've never used ISIS (haven't been able to justify the cost) so I don't know.... From the time stamp it looks like you're doing a A to D conversion in a quite tight loop, I don't know if that's a possible problem. It think you're going to have to post more of the code.

Finally, it's not an error, it's message telling you that it has happend. It doesn't prevent the code form compiling or from running but the behaviour of the code, as written, might not be what you actually wanted.

/Henrik.

[fratello]

Thank You so much for reply !
The rest of code is :

main:
pause 200
 ADCON0.1 = 1
 WHILE ADCON0.1 = 1 : WEND
 adval.HighByte = ADRESH
 adval.LowByte = ADRESL
 if k=0 and adval > 10 and adval < 750 then
 k=1
 pause 250
 endif

 while k=1
 gosub start
 wend
 goto main


start:

 ADCON0.1 = 1
 WHILE ADCON0.1 = 1 : WEND
 adval.HighByte = ADRESH
 adval.LowByte = ADRESL
if adval > 10  AND adval < 103 then gosub VolDn     

return

[HenrikOlsson]

Hi,

>The rest of code is :

Is it? You're calling VolDn but I don't see that in the code but I guess there's nothing to do with the ADC there?

Anyway, have you tried using ADCIN just to see if the message from ISIS goes away then?
I'm asking beacuse the DEFINE ADC_SAMPLUS 50 is for use with the ADCIN command I don't think it does anything for you when you run the ADC "manually". Alternativaly, whenever you're doing a converstion try:

ADCON0 = %10001001    ' Right justify, VRef=Vdd, select AN2, enable ADC.
PAUSEUS 100     
ADCON0.1 = 1          ' Start conversion
WHILE ADCON0.1 = 1 : WEND
adval.HighByte = ADRESH
adval.LowByte = ADRESL

In this case I don't think anything of it really matters since you're always sampling the same channel but it might be worth a try just to see if ISIS stops generating the message.

Finally, you're doing DEFINE ADC_CLOCK 3 but then you're overriding that by manually setting ANSEL to %00010100 which will set the ADC Clock to FOsc/8 instead of FRC. I don't think that's a problem in this case though.

/Henrik.

[fratello]

Thank you verry much !
Indeed, my mistake was the overriding of defines ...I didn't know until today the things You've posted. Hm ... so much to learn ! I'm glad I met people like You and other kindly members of this forum !
Best regards !

[fratello]

Me, again ...with something strange (at least for me) !
I try to use ADC for reading a couple of buttons. I have two situations :
- three buttons, with 82 ohms, 164 ohms, 1448 ohms resistors ; ADC reading = 1023 nothing pressed ; 78 with button 1 pressed ; 144 with button 2 ; 605 with button 3 ;
- three buttons, with 300 ohms, 1300 ohms, 3110 ohms AND 100 Kohms in parallel ; ADC reading = 1013 nothing pressed ; 236 with button 1 pressed; 575 with button 2 ; 768 with button 3.

I tried with 2 version of code (for both situations):

 ADCON0.1 = 1
 WHILE ADCON0.1 = 1 : WEND
 adval.HighByte = ADRESH
 adval.LowByte = ADRESL
if adval > 10  and adval < 300 then  gosub LED1
...etc....

and

ADCIN 3, adval
if adval > 10 and adval < 300 then gosub LED1
...etc...

For first situation everything works fine, with both version of reading ADC !
BUT ... for second situation, NOTHING HAPPENS !!! I really not understand what I do wrong ... Can me point to the right direction ? Thanks in advance !

[Acetronics2]

may be we could suspect the debounce time for your switches ... 50 µs is rather a short time !

did you try to use a little pause for settling ???

Alain

[fratello]

Thank you !
That means to add something like "Pause 50" before or after ADCIN command ?

[Acetronics2]

Here you can find an example ( in assembler ... YES ! ) that shows how it is done.
http://www.piclist.com/techref/micro...x4key1ad7r.htm

did you also read that one ???
http://www.picbasic.co.uk/forum/showthread.php?t=17956

Alain

[fratello]

Thanks ! But still no have answers on my problem ...

[Gusse]

Hi Fratello,

1) Do you have two PCB with different resistor values?
or
2) Have you changed resistors to same board and tested with two SW settings?

In case
1) there must be some other differences on PCB
2) resistors are not with correct values

[fratello]

Thanks, Mr. Gusse, for support !
I have only one PCB, without the resistors from chain (just R2=1k is soldered on PCB, between +5V and ADC_IN).
I put the resistors from chain 1 from R2/ADC_IN to ground ; in first case works perfect.
Then I soldered the R9=100k from R2/ADC_IN to ground ; I put resistors from chain 2 into circuit (in parallel with R9). In this case nothing happens.
All the resistors are measured, look to be OK (this was my first concern too ...).

Tomorrow I'm going to try to set some debounce ...

[fratello]

Update picture...

[grahamg]

I think you may wat to try the following: if (vala >650) and (vala <920) then go sub xx