 Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me. |
Forum Index : Microcontroller and PC projects : Enhancing Pi Pico Voltage measurement
| Author | Message | ||||
OA47 Guru  Joined: 11/04/2012 Location: AustraliaPosts: 1037 |
I want to get a Pi Pico to accurately measure voltages on an analog input. I have been using the attached input circuit to auto range by outputting a ground from a dig out pin to alter the voltage divider hence the range for the measured voltage.  R1=1M0 R2=10K R3=100K R4=1M0 (R4 is always grounded) D1=Schottky Diode Here is a snippet of code I was using for the F4 ArmMite. ' Autoranging here Vm=Pin(PA0): Pause 100 Volts=103.05*Vm 'CALIBRATION EQUATION If Volts < 20 Then Pin(PA1)=1:Pin(PA2)=0 '20V setting Vm=Pin(PA0): Pause 100 Volts=12.05*Vm 'CALIBRATION EQUATION BL=1:BEEP EndIf If Volts < 2 Then Pin(PA1)=1:Pin(PA02)=1 '2V setting ' Pin(PA3)=0 Vm=Pin(PA0): Pause 100 Volts=2.05*Vm 'CALIBRATION EQUATION BL=1:BEEP EndIf If Volts > 9.999 Then V$=Str$(Volts,2,2) Else V$=Str$(Volts,1,3) Text MM.HRes/2, MM.VRes/2 - 30,V$ , CM, 6, 2, RGB(white) ' This code to emulate decimal point not available on first fonts ' If Mid$(V$,2,1)="." Then Offset=95 ' If Mid$(V$,3,1)="." Then Offset=155 ' Circle Offset, 130, 6, 0, 1, 0, RGB(white) Text 150, 160, Date$, CM, 2, 1, RGB(Green) Text 150, 190, "UTC "+Time$, CM, 2, 1, RGB(Green) Offset=0 DrawButton 0, 0, 0, 210, 90, 30, RGB(Red), "EXIT" DrawButton 1, 0, 110, 210, 100, 30, c.ghosttext, "HOLD" DrawButton 2, 0, MM.HRes-90, 210, 90, 30, c.ghosttext, "LOG V" ' CheckButtonRelease btn If LogV=1 Then 'Log every 10 seconds If Right$(Time$,1)="0" Then Print "UTC,";Date$;",";Time$;",";V$ Pause 800 EndIf If LogV=2 Then 'Log every minute If Right$(Time$,2)="00" Then Print "UTC,";Date$;",";Time$;",";V$ Pause 500 EndIf If LogV=3 Then 'Log every hour If Right$(Time$,4)="0:00" Then Print "UTC,";Date$;",";Time$;",";V$ Pause 500 EndIf Loop WatchDog 4000 End Sub Can anyone help with suggestions to improve accuracy with the input circuit or the software? OA47 |
||||
TassyJim Guru Joined: 07/08/2011 Location: AustraliaPosts: 6479 |
The Pico doesn't do Open collector DOUT. Jim VK7JH MMedit |
||||
phil99 Guru Joined: 11/02/2018 Location: AustraliaPosts: 3042 |
Yes, a bit annoying that. In some situations you can simulate it with a diode, cathode to the pin (Schottky is best). In this case the non-linearity of a diode would affect accuracy so you need to do it with SetPin commands. PIN(x) = 0 : SETPIN x, DOUT 'switch to ground SETPIN x, OFF 'open collector (drain) |
||||
 Print this page |
 |
The Back Shed's forum code is written, and hosted, in Australia. | © JAQ Software 2026 |
