SOLVED: How can I reduce ADC jitter

[richard]

the problem you see does not exist , its the scopes reaction to having an large antenna [YOUR HAND] capacitively coupled to all of its inputs providing an overwhelming signal on it most sensitive ac input range, the scope is unable to provide the dc bias needed to keep the traces aligned in the overwhelmed state

[Demon]

the problem you see does not exist , its the scopes reaction to having an large antenna [YOUR HAND] capacitively coupled to all of its inputs providing an overwhelming signal on it most sensitive ac input range, the scope is unable to provide the dc bias needed to keep the traces aligned in the overwhelmed state

Excellent, so this won't be an issue since the drop-down circuit will be linked directly the the main board by headers.

[richard]

I try to keep my development code as close to final as possible, cause I know I'll forget to change stuff back. At least this way I can fire and forget the pin initialization

.


grounding unused pins and setting them as outputs is pointless , useless and potentially catastrophic


just leaving them as analog is ten times easier and can never do any harm, setting them as input with wpu on is also ok and can never do any harm

if the device is not battery powered its not worth any sort of effort

[Demon]

- digital input,
- weak pull-up ON,
- pin not connected.

I try to stay away from analog settings; no idea why. Maybe cause I started using only digital way back when.

https://skills.microchip.com/introdu...tecture/691929

Unit will always be powered by wall adapter, or possibly USB; but never battery..

[Demon]

According to this:

https://skills.microchip.com/introdu...tecture/691929

The pull-up is disabled automatically when either TRIS is set to an output or the pin is set as an analog input. These changes to TRIS and ANSEL will override WPU settings.

I can just set all pull-ups ON, leave the unused pins unconnected and forget about them. Then use the others as I wish in ANSEL and TRIS.

The only times I need to be concerned with WPU is on pins that must not be disturbed for whatever special reason.

WPUA = %11111111    '----------------------------------------------------------------'
WPUB = %11111111    '           ALWAYS SET WEAK PULL-UPS ON ALL PINS FIRST           '
WPUC = %11111111    '----------------------------------------------------------------'
                    '       CHANGES TO ANSEL AND TRIS WILL OVERRIDE AS REQUIRED      '
                    '----------------------------------------------------------------'

ANSELA = %00000010                      ' Pin A3 = SW input                 not implemented yet
                                        ' Pin A2 = ADC (B5K)                not implemented yet
                                        ' Pin A1 = ADC (B5K)
                                        ' Pin A0 = ADC (voltage divider)    not implemented yet
ANSELB = %00000000
ANSELC = %00000000

TRISA = %00000010                       ' Pin A3 = SW input                 not implemented yet
                                        ' Pin A2 = ADC input 2              not implemented yet
                                        ' Pin A1 = ADC input 1
                                        ' Pin A0 = ADC input 0              not implemented yet
TRISB = %00000000                       ' Pin B7 = ...not available, ICSPDAT
                                        ' Pin B6 = ...not available, ICSPCLK
TRISC = %11000000                       ' Pin C7 = RX      *** Datasheet requirement, INPUT ***
                                        ' Pin C6 = TX      *** Datasheet requirement, INPUT ***

EDIT: I can even leave PORT at the top in case a pin is left as analog output.

PORTA = %00000000                       '-------------------------------------------' 
PORTB = %00000000                       '       ALWAYS SET PINS LOW FIRST           '
PORTC = %00000000                       '-------------------------------------------'

Or did I miss something important...?

[richard]

it looks to me that you are creating problems and complications trying to solve a problem that does not exist.
generic pin control solutions will never work for all chips, there are too many chip variations.

pic pins to date always default to inputs, analog if possible. leave them that way unless you need one to be different.
each and every pin you employ needs to configured to suit its usage

mcc makes it easy

[Demon]

it looks to me that you are creating problems and complications...

My memory is getting worse by the year. That's why I try ways to set my code so it's easy to copy and modify for future modules. Of course it rarely works.

Having WPUA.1 = 1 caused leakage to VSS; it wasn't completely 0; varying in the 1.1mV range. My ADC reading never reached 0.

I took out the Port = 0 settings, set WPU properly instead of leaving ANSEL/TRIS override it, and now my ADC reading varies from 0 to 1.

WPUA = %11111101    '----------------------------------------------------------------'
WPUB = %11111111    '           ALWAYS SET WEAK PULL-UPS ON ALL PINS FIRST           '
WPUC = %11111111    '----------------------------------------------------------------'
                    '       CHANGES TO ANSEL AND TRIS WILL OVERRIDE AS REQUIRED      '
                    '----------------------------------------------------------------'

ANSELA = %00000010                      ' Pin A3 = SW input                 not implemented yet
                                        ' Pin A2 = ADC (B5K)                not implemented yet
                                        ' Pin A1 = ADC (B5K)
                                        ' Pin A0 = ADC (voltage divider)    not implemented yet
ANSELB = %00000000
ANSELC = %00000000

TRISA = %00000010                       ' Pin A3 = SW input                 not implemented yet
                                        ' Pin A2 = ADC input 2              not implemented yet
                                        ' Pin A1 = ADC input 1
                                        ' Pin A0 = ADC input 0              not implemented yet
TRISB = %00000000                       ' Pin B7 = ...not available, ICSPDAT
                                        ' Pin B6 = ...not available, ICSPCLK
TRISC = %11000000                       ' Pin C7 = RX      *** Datasheet requirement, INPUT ***
                                        ' Pin C6 = TX      *** Datasheet requirement, INPUT ***