SOLVED: How can I reduce ADC jitter

[Demon]

SOLVED: Noisy VDD/VSS using DC-DC converter. ADC stopped bouncing after using a 7805.

https://picbasic.co.uk/forum/showthr...527#post156527

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16F18877

- Using fixed input on ADC pin (1K to VDD, 1K to VSS - simulating pot at 50%)
- The ADC will drift from 498 to 509.

HSEROUTs on Serial Communicator:

Low=00498 High=00509

Is there anything in the registers that I can "tune" for the ADC?

#CONFIG
    __config _CONFIG1, _FEXTOSC_OFF & _RSTOSC_HFINT32 & _CLKOUTEN_OFF & _CSWEN_OFF & _FCMEN_ON
    __config _CONFIG2, _MCLRE_ON & _PWRTE_OFF & _LPBOREN_OFF & _BOREN_ON & _BORV_LO & _ZCD_OFF & _PPS1WAY_OFF & _STVREN_ON & _DEBUG_OFF
    __config _CONFIG3, _WDTCPS_WDTCPS_11 & _WDTE_OFF & _WDTCWS_WDTCWS_7 & _WDTCCS_LFINTOSC
    __config _CONFIG4, _WRT_OFF & _SCANE_available & _LVP_OFF
    __config _CONFIG5, _CP_OFF & _CPD_OFF
#ENDCONFIG

DEFINE OSC 32

DEFINE  ADC_BITS 10                 ' 10-bit Analog to digital

define  CCP1_REG     0              ' Must clear unused CCP pins or else unpredictable results
DEFINE  CCP1_BIT     0
define  CCP2_REG     0
DEFINE  CCP2_BIT     0
DEFINE  CCP3_REG     0
DEFINE  CCP3_BIT     0
define  CCP4_REG     0
DEFINE  CCP4_BIT     0
define  CCP5_REG     0              ' Must clear unused CCP pins or else unpredictable results
DEFINE  CCP5_BIT     0

DEFINE  HSER_RXREG PORTC
DEFINE  HSER_RXBIT 7
DEFINE  HSER_TXREG PORTC
DEFINE  HSER_TXBIT 6

DEFINE  HSER_RCSTA 90h              ' Enable serial port & continuous receive
DEFINE  HSER_TXSTA 24h              ' Enable transmit, BRGH = 1
Define  HSER_BAUD 115200
DEFINE  HSER_CLROERR 1              ' Clear overflow automatically
DEFINE  HSER_SPBRGH  0
DEFINE  HSER_SPBRG  68

BAUDCON.3 = 1                       ' Enable 16 bit baudrate generator

RA4PPS = 0                          ' Disable CCP5
RB0PPS = 0                          ' Disable CCP4
RB5PPS = 0                          ' Disable CCP3
RC1PPS = 0                          ' Disable CCP2
RC2PPS = 0                          ' Disable CCP1

IOCAP = %00000000                               'IOC Positive Edge, low-to-high
IOCAN = %00000000                               'IOC Negative Edge, from high-to-low
IOCBP = %00000000                               'IOC Positive Edge, low-to-high
IOCBN = %00000000                               'IOC Negative Edge, from high-to-low
IOCCP = %00000000                               'IOC Positive Edge, low-to-high
IOCCN = %00000000                               'IOC Negative Edge, from high-to-low
'IOCDP = %00000000                              '...not available
'IOCDN = %00000000                              '...not available
'IOCEP = %00000000                              '...not available
'IOCEN = %00000000                              '...not available

WPUA = %00000000                        ' Pull-up resistors
WPUB = %00000000
WPUC = %00000000
WPUD = %00000000
WPUE = %00000000

INLVLA = %00000000                      ' TTL input level
INLVLB = %00000000
INLVLC = %00000000
INLVLD = %00000000
'INLVLE = %00000000                      ' ...only available on E3 / MCLR pin

ADCON0 = %10000100                      ' ADC CONTROL REGISTER 0
ADCLK  = %00111111                      ' ADC CLOCK SELECTION REGISTER
'ADPCH  = %00011010                      ' Channel 26 - D2

ANSELA = %00000000
ANSELB = %00000000
ANSELC = %00000000
ANSELD = %00000110                      ' Pin D2 = ADC input, NavCom
                                        ' Pin D1 = ADC input, Glareshield
ANSELE = %00000000

TRISA = %00000000                       
TRISB = %00000000                       
TRISC = %00000000                       
TRISD = %00000110                       
TRISE = %00000000

include "I:\Project_v2\PBP\PBP_Includes\USART.bas"

ADCInput                var word

LowADC                  var word
HighADC                 var word

    Pause 1                                     ' Let PIC stabilize

    LowADC = 1023
    HighADC = 0
    AdcInput = 0

Mainloop:

    adcin 26, AdcInput
    
    if AdcInput < LowADC then LowADc = AdcInput
    if AdcInput > HighADC then HighADC = AdcInput
        
    hserout [   "Low=", dec5 LowADC, "  High=", DEC5 HighADC, 10  ]                             
 
    goto mainloop
end

I was getting desperate with the drift on the pots, so I thought I'd do a control run using resistors.

I expected it to remain the same or very close, but I'm still getting drift.