ADC Help Please

I'm having some trouble with the analog inputs on a 16F886. Code is shown below. Most of it is commented out right now, so it's just an initial LED flash, analog in, heartbeat routine. I want to use AN0(RA0), AN1(RA1) and AN4(RA5) as analog inputs. If I comment out all of the ADCIN instructions, the LED flashes away as it should. If I uncomment any of the ADCINs, the heartbeat LED just stays on. It seems I'm doing something wrong with either the ADC configuration or the actual ADCIN command, but what? I had something very similar to this working fine on a 16f690, but changing over to the 16F886 has caused me some problems. This is new for me, so any comments/suggestions on programming style, etc. would be welcome. Thanks.

BrianB

define OSC 4
Define ADC_BITS 8 ' Set number of bits in result
Define ADC_CLOCK 3 ' Set clock source (3=rc)
Define ADC_SAMPLEUS 50 ' Set sampling time in uS

'CM1CON0 = 0 ' Comparators off (Do I need these?)
'CM2CON0 = 0 ' Comparators off
ANSEL = %00010011' Set analog pins
ANSELH = %00000000
TRISA = %00100011' Set port A
TRISB = %11000000 ' Set port B
TRISC = %00000000 ' Set port C

ANIN0 var WORD 'Cylinder 1 Feedback Pot
ANIN1 var WORD 'Cylinder 2 Feedback Pot
SW1EXT var bit 'Extend Switch
SW2RET var Bit 'Retract Switch
EXT1FLAG VAR Bit
RET1FLAG VAR Bit
EXT2FLAG var bit
RET2FLAG var bit
J var WORD

'Initialize Variables and Ports
PORTA=0
PORTB=0
PORTC=0
EXt1flag=0
ext2flag=0
ret1flag=0
ret2flag=0

for j=1 to 25 'Startup indicator
toggle PortA.2
pause 50
next j

MAIN:
FOR j=1 TO 500
Adcin 4, ANIN0
'Poll Switches
'If PortB.7=0 then
' pause 20
' if PORTB.7=0 then
' SW1EXT=1
' endif
'Else
' SW1EXT=0
'ENDIF
'If PortB.6=0 then
' pause 20
' if PORTB.6=0 then
' SW2RET=1
' endif
'else
' SW2RET=0
'endif
'adcin 0, ANIN0 'Cylinder 1 Pot
'IF ANIN0<245 then
' EXT1FLAG=0 'OK to Extend
'Else
' EXT1FLAG=1
'endif
'IF ANIN0>10 then
' RET1FLAG=0 'OK to Retract
'else
' RET1FLAG=1
'ENdif
'ADCIN 1, ANIN1 'Cylinder 2 Pot
'IF ANIN1<245 then
' EXT2FLAG=0 'OK to Extend
'Else
' EXT2FLAG=1
'endif
'IF ANIN1>10 then
' RET2FLAG=0 'OK to Retract
'else
' RET2FLAG=1
'ENdif

'IF (SW1EXT=1) and (EXT1FLAG=0) then 'Extend Cylinder 1
' PORTB.3=1
' PORTB.4=0
' PORTB.5=1
'endif
'IF (SW1EXT=1) and (EXT1FLAG=1) then 'Stop Cylinder 1
' PORTB.3=0
' PORTB.4=0
' PORTB.5=0
'ENDIF
'IF (SW2RET=1) and (RET1FLAG=0) then 'Retract Cylinder 1
' PORTB.3=0
' PORTB.4=1
' PORTB.5=1
'endif
'IF (SW2RET=1) AND (RET1FLAG=1) then 'Stop Cylinder 1
' PORTB.3=0
' PORTB.4=0
' PORTB.5=0
'endif
'IF (SW1EXT=1) and (EXT2FLAG=0) then 'Extend Cylinder 2
' PORTB.0=1
' PORTB.1=0
' PORTB.2=1
'endif
'IF (SW1EXT=1) and (EXT2FLAG=1) then 'Stop Cylinder 2
' PORTB.0=0
' PORTB.1=0
' PORTB.2=0
'ENDIF
'IF (SW2RET=1) and (RET2FLAG=0) then 'Retract Cylinder 2
' PORTB.0=0
' PORTB.1=1
' PORTB.2=1
'endif
'IF (SW2RET=1) AND (RET2FLAG=1) then 'Stop Cylinder 2
' PORTB.0=0
' PORTB.1=0
' PORTB.2=0
'endif
'if (SW1EXT=0) and (SW2RET=0) then 'Stop Cylinders
' PORTB.3=0
' PORTB.4=0
' PORTB.5=0
' PORTB.0=0
' PORTB.1=0
' PORTB.2=0
'endif
'if SW1EXT=1 and SW2RET=1 then 'Stop Cylinders
' PORTB.3=0
' PORTB.4=0
' PORTB.5=0
' PORTB.0=0
' PORTB.1=0
' PORTB.2=0
'endif
'if (ANIN0>ANIN1) AND (SW1EXT=0) AND (SW2RET=0) THEN
' GOSUB SLAVE1
'ENDIF
'IF (ANIN1>ANIN0) AND (SW1EXT=0) AND (SW2RET=0) THEN
' GOSUB SLAVE2
'ENDIF

NExt J
toggle PORTA.2 'Heartbeat LED
pause 500
goto main

'SLAVE1:
'IF (ANin0-ANin1)>=5 THEN
' PORTB.0=1
' PORTB.1=0
' PORTB.2=1
'ENDIF
'if (ANin0-ANin1)<5 THEN
'PORTB.0=0
'PORTB.1=0
'PORTB.2=0
'ENDIF
'RETURN

'SLAVE2:
'IF (ANin1-ANin0)>=5 THEN
' PORTB.0=0
' PORTB.1=1
' PORTB.2=1
'ENDIF
'IF (ANin1-ANin0)<5 THEN
'PORTB.0=0
'PORTB.1=0
'PORTB.2=0
'ENDIF
'RETURN

I'll try it here, but i think it has something to do with the WORD variable inside a ADCIN setuped for 8 bit results... not sure yet. I have to find those 886 here first... What a messy bench i have in front of me http://www.mister-e.org/Pics/ROFL

OK it's true, ADCIN do something bad on this chip, now i have to find why. In meantime use something like

Code:

 DEFINE OSC 4 ADCON0=%11000001 ADCON1=%00000000 GoDone VAR ADCON0.1 '76543210 CHSELECT VAR BYTE CM1CON0 = 0 ' Comparators off (Do I need these?) CM2CON0 = 0 ' Comparators off ANSEL = %00010011' Set analog pins ANSELH = %00000000 TRISA = %00100011' Set port A TRISB = %11000000 ' Set port B TRISC = %00000000 ' Set port C ANIN0 VAR BYTE 'Cylinder 1 Feedback Pot ANIN1 VAR BYTE 'Cylinder 2 Feedback Pot SW1EXT VAR BIT 'Extend Switch SW2RET VAR BIT 'Retract Switch EXT1FLAG VAR BIT RET1FLAG VAR BIT EXT2FLAG VAR BIT RET2FLAG VAR BIT J VAR WORD 'Initialize Variables and Ports PORTA=0 PORTB=0 PORTC=0 EXT1FLAG=0 EXT2FLAG=0 RET1FLAG=0 RET2FLAG=0 GOTO START ASM ADC_IN MACRO CHANNEL, VARIABLE MOVE?CB CHANNEL, _CHSELECT L?CALL _DO_AD_CONVERSION MOVE?BB ADRESH,VARIABLE ENDM ENDASM DO_AD_CONVERSION: ADCON0=(CHSELECT<<2) |%11000001 PAUSEUS 50 GoDone=1 WHILE GoDone : WEND RETURN START: FOR J=1 TO 25 'Startup indicator TOGGLE PortA.2 PAUSE 50 NEXT J MAIN: FOR J=1 TO 500 @ ADC_IN 4,_ANIN0 'Poll Switches IF PortB.7=0 THEN PAUSE 20 IF PORTB.7=0 THEN SW1EXT=1 ENDIF ELSE SW1EXT=0 ENDIF IF PortB.6=0 THEN PAUSE 20 IF PORTB.6=0 THEN SW2RET=1 ENDIF ELSE SW2RET=0 ENDIF @ ADC_IN 0,_ANIN0 IF ANIN0<245 THEN EXT1FLAG=0 'OK to Extend ELSE EXT1FLAG=1 ENDIF IF ANIN0>10 THEN RET1FLAG=0 'OK to Retract ELSE RET1FLAG=1 ENDIF @ ADC_IN 1,_ANIN1 IF ANIN1<245 THEN EXT2FLAG=0 'OK to Extend ELSE EXT2FLAG=1 ENDIF IF ANIN1>10 THEN RET2FLAG=0 'OK to Retract ELSE RET2FLAG=1 ENDIF IF (SW1EXT=1) AND (EXT1FLAG=0) THEN 'Extend Cylinder 1 PORTB.3=1 PORTB.4=0 PORTB.5=1 ENDIF IF (SW1EXT=1) AND (EXT1FLAG=1) THEN 'Stop Cylinder 1 PORTB.3=0 PORTB.4=0 PORTB.5=0 ENDIF IF (SW2RET=1) AND (RET1FLAG=0) THEN 'Retract Cylinder 1 PORTB.3=0 PORTB.4=1 PORTB.5=1 ENDIF IF (SW2RET=1) AND (RET1FLAG=1) THEN 'Stop Cylinder 1 PORTB.3=0 PORTB.4=0 PORTB.5=0 ENDIF IF (SW1EXT=1) AND (EXT2FLAG=0) THEN 'Extend Cylinder 2 PORTB.0=1 PORTB.1=0 PORTB.2=1 ENDIF IF (SW1EXT=1) AND (EXT2FLAG=1) THEN 'Stop Cylinder 2 PORTB.0=0 PORTB.1=0 PORTB.2=0 ENDIF IF (SW2RET=1) AND (RET2FLAG=0) THEN 'Retract Cylinder 2 PORTB.0=0 PORTB.1=1 PORTB.2=1 ENDIF IF (SW2RET=1) AND (RET2FLAG=1) THEN 'Stop Cylinder 2 PORTB.0=0 PORTB.1=0 PORTB.2=0 ENDIF IF (SW1EXT=0) AND (SW2RET=0) THEN 'Stop Cylinders PORTB.3=0 PORTB.4=0 PORTB.5=0 PORTB.0=0 PORTB.1=0 PORTB.2=0 ENDIF IF SW1EXT=1 AND SW2RET=1 THEN 'Stop Cylinders PORTB.3=0 PORTB.4=0 PORTB.5=0 PORTB.0=0 PORTB.1=0 PORTB.2=0 ENDIF IF (ANIN0>ANIN1) AND (SW1EXT=0) AND (SW2RET=0) THEN GOSUB SLAVE1 ENDIF IF (ANIN1>ANIN0) AND (SW1EXT=0) AND (SW2RET=0) THEN GOSUB SLAVE2 ENDIF NEXT J TOGGLE PORTA.2 'Heartbeat LED PAUSE 500 GOTO MAIN SLAVE1: IF (ANIN0-ANIN1)>=5 THEN PORTB.0=1 PORTB.1=0 PORTB.2=1 ENDIF IF (ANIN0-ANIN1)<5 THEN PORTB.0=0 PORTB.1=0 PORTB.2=0 ENDIF RETURN SLAVE2: IF (ANIN1-ANIN0)>=5 THEN PORTB.0=0 PORTB.1=1 PORTB.2=1 ENDIF IF (ANIN1-ANIN0)<5 THEN PORTB.0=0 PORTB.1=0 PORTB.2=0 ENDIF RETURN

something is bad with ADCIN with this chip, so before breaking something i will ask Charles at Melabs.

In meantime the above solution or manually set/read register method still work.

Compare ADCON0 & ADCON1 in the 16F690 & 16F886 data sheets. ADCON0
and ADCON1 are different. Microchip shifted things around again, so ADCIN
library will need some tweaking to work with this one.

I would just configure A/D regs manually, and forget about ADCIN.

Yup, i had an answer from Charles that confirm a issue of those 16F88x serie. He suggest this work around

Code:

DEFINE ADC_BITS 8 ' ADCIN resolution (Bits) DEFINE ADC_CLOCK 0 ' Work around that sets Vref bits in ADCON1 DEFINE ADC_SAMPLEUS 50 ' ADC sampling time (uSec) ADCON0=ADCON0 | %11000000 ' Work around that sets ADCS in ADCON0

i've tested it here, and it's working. So now, you have 2-3 different way to make it work.

Works great now. Thanks.

BrianB

Hi everyone,
I am following up on that ADC config issue, as I have troubles to make my project (based on a 16F884) to work.

Here is the hardware part:

The project is a nixie clock with other fancy stuffs (thermometer, hygrometer...). That is, I use the analog module to read various sensors. Additionally, due to the lack of I/O, I use an "analog" keypad consisting of 3 pushbuttons that each produce a different voltage (with resistor combinations).

So far, I can only get erratic values out of the ADC no matter which A/D pin I'm reading... It is varying as if the pin was connected to an antenna and reading noise (with completely random variations from min to max!). I also tried to ground one of the analog I/O to read it, and the results are actually pulled towards 0, but can still get as high as 300.

I don't thing the hardware is wrong on that one, I have a steady 5V powersupply, checked with a scope, also sensor output were checked and don't fluctuate more than a few mV. I also included capacitors between inputs and ground... and everything is mounted on a nice dual side PCB.

The only source of noise would be my buck-boost switch, that I use to get the 180V for the tubes, but I don't see much noise when I look on the analog lines with my scope.

This is why i'm suspecting a software or config problem, but can't work it out. And since there's issue with this family I'd like to make sure i'm not doing anything wrong.
Here is parts of my program, I added the workaround posted above in the config:

DEFINE OSC 20
DEFINE LOADER_USED 1

'set up the ADC with special workaround for the 16F88x family
DEFINE ADC_BITS 10 ' ADCIN resolution (Bits)
DEFINE ADC_CLOCK 0 ' Work around that sets Vref bits in ADCON1
DEFINE ADC_SAMPLEUS 50 ' ADC sampling time (uSec)
ADCON0=ADCON0 | %11000000 ' Work around that sets ADCS in ADCON0

'Set oscillator configuration to run on external oscillator
OSCCON = %00000000

'Set comparators off
CM1CON0 = %00000000
CM2CON0 = %00000000

'Set analog input AN0, AN1, AN2, AN3, AN4 and AN5
ANSEL = %00011111
ANSELH = %00000000
ADCON1 = %00000000
'ADCON0 = %01000001

'Set PortA as input or output
PORTA = %00000000
TRISA = %00101111
'Set entire PortB as digital input
PORTB = %00000000
TRISB = %00000000
'Set entire PortC as digital input
PORTC = %00000000
TRISC = %00000000
'Set entire PortD as digital input
PORTD = %00000000
TRISD = %00000000
'Set PortE0 as input or output
PORTE = %00000000
TRISE = %00000001

---------------------------

'************************************************* ******
'Read the keypad
'************************************************* ******
ReadPushButtons:
'Mode/UP 0.47V
'Date/DOWN 2.6V
'SET 5.0V

ADCIN 5, ButtonValue

Return

---------------------------

All other (non analog) functions are working great otherwise...!
Any help apreciated :)

1 = Input
0 = Output

Hmm good catch! I forgot AN5 which was purposedly the one I'm trying to read...!

Here is ANSEL now:
'Set analog input AN0, AN1, AN2, AN3, AN4 and AN5
ANSEL = %00111111

However that hasn't changed anything, for AN5 or the other sensors (AN4 to AN0).

Going through the 16F884 datasheet again to check these registers.

I remember doing this lately on a 16F877A whithout much troubles!

Compiler version?

It is PBP 2.50

Take the advise from Bruce in post 5.
Here is an example for a different chip, but you will get the idea. Works much nicer.
http://rentron.com/PICX2.htm

And it may not be causing you trouble now but it could ...Maybe you got my hint...

Quote:

'Set entire PortB as digital input
PORTB = %00000000
TRISB = %00000000
'Set entire PortC as digital input
PORTC = %00000000
TRISC = %00000000
'Set entire PortD as digital input
PORTD = %00000000
TRISD = %00000000

1 = Input
0 = Output

I will try to read the ADC manually then,

And I missed your hint, because the code is working for those I/O's (however the comments are wrong!).

Quote:

'Set entire PortB as digital output
PORTB = %00000000
TRISB = %00000000
'Set entire PortC as digital output
PORTC = %00000000
TRISC = %00000000
'Set entire PortD as digital output
PORTD = %00000000
TRISD = %00000000

Looks better now :D

Ok, I just tried to recompile my code for a 16F877A and if does work much better. Values are still fluctuating a bit so I will have to find a way to stabilize this (using software and or hardware).

here is the new init code

'************************************************* ******
'Init for PIC16F877A
'************************************************* ******

'Set ADC pins to digital operation
ADCON1 = %10001001 'AN0 to AN5 are analog input
CMCON = %00000111 'disabling the comparator module

'Define pin function
TRISA = %00101111 'Set PortA as input or output
TRISB = %00000000 'Set entire PortB as digital output
TRISC = %00000000 'Set entire PortC as digital output
TRISD = %00000000 'Set entire PortD as digital output
TRISE = %00000001 'Set PortE0 as input and rest as output

' Define ADCIN parameters
Define ADC_BITS 10 ' Set number of bits in result
Define ADC_CLOCK 3 ' Set clock source (3=rc)
Define ADC_SAMPLEUS 50 ' Set sampling time in uS

I thought I would use a 16F88x since the 877A is being phased out. Also I have a couple 884 on hand... but with all the extra trouble I think I will stick to the 877A to write the code and then transfer it to the 884 afterward.

Will update the status of the project here ;)

PS: as far as my noise problem comming from the HV generation circuit, I now switch off the PWM module that drive the switching mosfet slightly before doing my analog readings and they are now rock solid :)