Topic Author
Posts: 16
Joined: 25 Sep 2018, 10:17

Understanding the process image and pitest

09 Jun 2019, 20:22

I am using the RevPi Connect with some sensors connected as RTU slaves.
I am reading 20 word-sized registers (some of which to be interpreted as IEE754 later) from them.
I put the read values in Input_Word_1, Input_Word_21, Input_Word_21 etc just adding the number of registers read each time.

I am not sure I understand how the pitest and registers from process image actually works.

I want to read the registers from the sensors every 1 minute and write the values to a file.
I have configured the RTU Master correctly I think, but are the actual values stored in Input_Word_1, Input_Word_2, Input_Word_3.... etc naming words 1..20 or are the Input Words only pointers into a structure/array that I have to acces using the info in Input_Word_1, Input_Word_21, Input_Word_41 .. ??

Clarification ; I have used a loop writing Input_Word_$i where i goes from 1 to 20, but this tutorial - ... tu-master/ seems to indicate that the input Input_Word_1 must be accessed and parsed to access the actual data ?
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Posts: 198
Joined: 18 Jun 2018, 16:16

Re: Understanding the process image and pitest

12 Jun 2019, 14:00

Here you can find an explanation about PiControl, I think it will help you to understand it better.

Here is another example how you can access the process image with Python.
You can use for example the RevPiModIO2 library.

Before you can use this library, you have to install it first.
„sudo apt-get update“
“sudo apt-get install python3-revpimodio2“
Here is an example of how to use the library.
# -*- coding: utf-8 -*-
u"""Kleines Programm um zwei Eingänge zu prüfen und einen Ausgang zu sezten."""
import revpimodio2

# RevPiModIO instanziieren
rpi = revpimodio2.RevPiModIO(autorefresh=True)

def zyklus(ct):
    u"""Zyklusfunktion für Steuerung."""

    # Ausgang setzen wenn I_1 und nicht I_2
    if and not = True

    # Ausgang rücksetzen wenn I_2 und nicht I_1
    if and not = False

print("gehe in loop")
print("programm ende")

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