Stable ADC readings

[mazoul72]

Hello,
i made this to programm ADC

bmf_comm1 VAR PORTB.0
bmf_comm2 VAR PORTB.1
'Variables
bmfsD VAR WORD
bmfs1D VAR WORD
iled var byte
blink1 var byte 'pour clignotement 1ère led
blink2 var byte 'pour clignotement 2ème led
'configuration du port pour lire l'entrée analogique
TRISA = %00000011 ' RA0 et RA1 en entrée
TRISB = %11111100 ' RB0 et RB1 en sortie
ADCON1 = $10000010 'RA0 à RA3

test_depart:
Low bmf_comm1
Low bmf_comm2
High bmf_comm1
high bmf_comm2
pause 2000
goto mainloop
'lecture de la valeur
getad:
PAUSEUS 50 ' Wait for A/D channel acquisition time
ADCON0.2 = 1 ' Start conversion
WHILE ADCON0.2 ' Wait for it to complete
WEND
Return

' Subroutine to get pot x value
getx:
ADCON0 = $41 ' Set A/D to Fosc/8, Channel 0, On
Gosub getad
bmfsD = ADRESL + (ADRESH*256)
Return

' Subroutine to get pot y value
gety:
ADCON0 = $49 ' Set A/D to Fosc/8, Channel 1, On
Gosub getad
bmfs1D = (ADRESH*256) + ADRESL
Return
val_leds:
low bmfs_comm1
low bmfs_comm2
gosub getx
gosub gety

if (bmfsD > 1000) Then Goto val_leds
if (bmfsD > 750) Then Goto boucle_led
if (bmfsD > 500) Then Goto boucle1_led
if (bmfsD > 250) Then Goto boucle2_led

High bmf_comm1
High bmf_comm2
pause 1500
goto val_leds
boucle_led:
iled = 0
while iled < 5
if iled = 1 or 3 or 5 then high blink1:low blink2
if iled = 0 or 2 or 4 then low blink1:high blink2
iled = iled + 1
pause 1000
wend
goto val_leds
boucle1_led:
High bmf_comm1
low bmf_comm2
pause 3000
goto val_leds
boucle2_led:
low bmf_comm1
high bmf_comm2
Goto val_leds
End

The leds works but always lightning , action on button (RB0 only for the moment) don't change anything.
No blinking .
I don't know what .
thanks.

[mister_e]

Salut et Bienvenue sur le forum

I haven't check the whole thing in deep but I think you should modify the boucle_led section to

boucle_led:
        iled = 0
        while iled < 5
                if iled = 1 or 3 or 5 then 
                        high blink1
                        low blink2     
                        endif
                        
                if iled = 0 or 2 or 4 then 
                        low blink1
                        high blink2
                        endif
                iled = iled + 1
                pause 1000
                wend
        goto val_leds

Probably it will solve your problem though... let me know the PIC you're using and your PBP version.

EDIT: Your code have 2 compilation error
1) no mainloop label
2) adcon1: the way you have written it, it's value should start with a % instead of a $

[mister_e]

Looking at your code, I guess it's your first program, There's quite a few mistakes in and it is also hard to follow what you want to do.

No problem, been there...done that. Tell us what you want to do and we could build something to help you to get started.

Tell us the PIC your're using and post your schematic if you have any, or describe it.

[mazoul72]

Sorry for double post but i tried many many modifications.
my pic is 16F877A , i desire to put multifunctions buttons of steering wheel and decode for command radio car system .
i make a test with leds for ADC value input .
Oh,oh,oh,
i have just see that i don't put MCLR to any connection , a resistor of 4.7kohms to +5V ?

It is a very simple schematic for test but the entire schematic is for steering wheel command and FIS Tachometer car display modification in live .
example : see the kwp1281 protocol codes of line K (not can bus) like VCDS soft but more simple.

This is the first part ( BMF )

For mainloop , it is because i modify the labels and i forgot it (val_leds) .
For $ , it is a mistake , THANKS.
i will try now

Regards

[mazoul72]

my leds light off after 2 sec , it is ok for starting (mainloop replaced by val_leds)
But after i have only two leds lightning together , it is not good with all boutons
and i have no blinking leds

And now i have no actions on leds (off always) , i don 't undertand why , AD not stable or other....
it is the same with or without MCLR .

[mister_e]

Ah ok I see, you read a voltage then act upon. Cool, I did something like that awhile back but it was for car remote starter purpose (Door lock, alarm bypass, Windows roll-up/down) Oh well, those were the days

Yes MCLR must be tied to Vdd. 4.7K is fine.

not sure of what you want to do and how it should flash your LEDs but try this one

        bmf_comm1   VAR PORTB.0
        bmf_comm2   VAR PORTB.1
        
        LEDBlinkRate CON 200
        
        'Variables
        bmfsD       VAR WORD
        bmfs1D      VAR WORD
        iled        var byte
        
        'configuration du port pour lire l'entrée analogique
        TRISA = %00000011       ' RA0 et RA1 en entrée
        TRISB = %11111100       ' RB0 et RB1 en sortie
       
        DEFINE ADC_BITS 10      ' Set number of bits in result
        DEFINE ADC_CLOCK 3      ' Set clock source (rc = 3)
        DEFINE ADC_SAMPLEUS 50  ' Set sampling time in 
        ADCON1 = %10000010      ' RA0 à RA3

test_depart:
        PORTB = 3               ' Turn ON PORTB<1:0>
        pause LEDBlinkRate      '  
       
val_leds:
        PORTB = 0               ' Turn OFF PORTB<1:0>
        PAUSE LEDBlinkRate        
        ADCIN 0,BMFSd           ' Read CH0
        ADCIN 1,BMFS1d          ' Read CH1
        if (bmfsD > 1000) Then val_leds
        if (bmfsD > 750)  Then boucle_led
        if (bmfsD > 500)  Then boucle1_led
        if (bmfsD > 250)  Then boucle2_led
        
        goto test_depart
        
boucle_led:
        PORTB = 1
        for ILED = 0 to 5
                PORTB = PORTB ^ 3
                PAUSE LEDBlinkRate
                NEXT
        goto val_leds
        
boucle1_led:
        High bmf_comm1
        pause LEDBlinkRate
        goto val_leds
        
boucle2_led:
        high bmf_comm2
        PAUSE LEDBlinkRate
        Goto val_leds
        End

seems to work for me here, 4MHz oscillator, some different led blinking opattern depending of the value of AN0.

[mazoul72]

Hello,

it still doesn't work ....I don't understand why .
The leds are still off whenever i select any buttons .
I see 3.96 V between middle point of my buttons and external pull up resistors (on RA0 and RA1) .
When i push buttons , i have 1.44V / 0.80 V / 0.40 V .
Whith quantum 4.88xxx mV , it gives to me 295 , 164 , 82 .
For 3.96V , 811 aproximatively .

LED replace resistors out (to test)

[mister_e]

Simple, there's no voltage in there as it is right now. You'll need to modify the circuit to add some voltage there. The pull-up thing should work.

Do yourself a big favor, output the value of the ADC reading to a LCD or to your computer, push on a single button, note the value and modify the IF-THEN value in the code.

What are your pull-up value?

[Ioannis]

On F877 or F877A there are NO pull-ups on port A. Only on Port B.

Ioannis