Mparadis at 20:06, 16 September 2025

2025-09-16T20:06:46Z

← Older revision		Revision as of 20:06, 16 September 2025
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	To determine which properties (if any) must be set, visit your device's [{{SERVER}}/?view=api API] and check the '''Channel Persistence''' checkbox:		To determine which properties (if any) must be set, visit your device's [{{SERVER}}/?view=api API] and check the '''Channel Persistence''' checkbox:

	[[Image:ChPersistCheckbox.jpg\|center\|link=https://~~wwwdev.int~~.phidgets.com/docs/images/d/dd/ChPersistCheckbox.jpg\|650px]]		[[Image:ChPersistCheckbox.jpg\|center\|link=https://cdn.phidgets.com/docs/images/d/dd/ChPersistCheckbox.jpg\|650px]]

	Then, scroll down to see which properties are labelled as "Must be set":		Then, scroll down to see which properties are labelled as "Must be set":

	[[Image:ChPersistMustSet.jpg\|center\|link=https://~~wwwdev.int~~.phidgets.com/docs/images/5/55/ChPersistMustSet.jpg\|650px]]		[[Image:ChPersistMustSet.jpg\|center\|link=https://cdn.phidgets.com/docs/images/5/55/ChPersistMustSet.jpg\|650px]]

	====Example====		====Example====

Mparadis: Created page with "{{#seo: |description=Enable channel persistence to maintain your device's output. }} Category:IntroGuide TOC ==What is Channel Persistence== By default, all properties of your Phidget are reset to default values if the channel is closed and opened again, or if your application stops running and is restarted. Enabling '''Channel Persistence''' allows the state of your channel to persist, even after your application has been closed or has stopped running. If the P..."

2025-09-16T20:04:17Z

Created page with "{{#seo: |description=Enable channel persistence to maintain your device's output. }} Category:IntroGuide __TOC__ ==What is Channel Persistence== By default, all properties of your Phidget are reset to default values if the channel is closed and opened again, or if your application stops running and is restarted. Enabling '''Channel Persistence''' allows the state of your channel to persist, even after your application has been closed or has stopped running. If the P..."

New page

{{#seo:
|description=Enable channel persistence to maintain your device's output.
}}
[[Category:IntroGuide]]
__TOC__
==What is Channel Persistence==
By default, all properties of your Phidget are reset to default values if the channel is closed and opened again, or if your application stops running and is restarted.

Enabling '''Channel Persistence''' allows the state of your channel to persist, even after your application has been closed or has stopped running. If the Phidget loses power (e.g. if it's unplugged from its USB or VINT connection) then it will not persist, event if persistence was enabled.

===Supported Channel Classes===
Channel Persistence is supported on most output-style devices:

* DigitalOutput
* LCD
* PowerGuard
* RCServo
* Stepper
* VoltageOutput

==Enabling Channel Persistence==
===Video Guide===
<center>{{#ev:youtube|aCLCdJ4OOI0|||||rel=0}}</center>

=== Adding Persistence to your Program ===

Persistence can be enabled simply by setting the '''{{Code|ChannelPersistence}}''' property of the channel. We recommend enabling it '''before''' opening the channel. You can still enable it after the channel is opened, but this would cause the outputs to briefly return to the default (off) state until your application reaches the point in the code where persistence is enabled.

When setting persistence before opening the channel, the library will attempt to read the state of the device, and any property that cannot be read will have an unknown value. This will happen the first time the application runs after the Phidget has been unplugged. In order to deal with the unknown values, certain properties must be set to a known state before you can interact with the channel. If you don't, you'll get an Unknown Value exception.

To determine which properties (if any) must be set, visit your device's [{{SERVER}}/?view=api API] and check the '''Channel Persistence''' checkbox:

[[Image:ChPersistCheckbox.jpg|center|link=https://wwwdev.int.phidgets.com/docs/images/d/dd/ChPersistCheckbox.jpg|650px]]

Then, scroll down to see which properties are labelled as "Must be set":

[[Image:ChPersistMustSet.jpg|center|link=https://wwwdev.int.phidgets.com/docs/images/5/55/ChPersistMustSet.jpg|650px]]

====Example====

Here's a simple VINT Hub digital output example with channel persistence. When this code is run the first time, the output will begin in the "off" state, and turn on after 500ms. The next time and any subsequent time it's run, the output will begin in the "on" state.

<tabber>
C#=<syntaxhighlight lang=cSharp>
using System;
using Phidget22;

namespace ConsoleApplication
{
class Program
{

static void Main(string[] args)
{
DigitalOutput digitalOutput0 = new DigitalOutput();

digitalOutput0.IsHubPortDevice = true;
digitalOutput0.HubPort = 0;

digitalOutput0.ChannelPersistence = true;

digitalOutput0.Open(5000);

Thread.Sleep(500);

digitalOutput0.DutyCycle = 1;

digitalOutput0.Close();
}
}
}
</syntaxhighlight>
|-|
Python=<syntaxhighlight lang=python>
from Phidget22.Phidget import *
from Phidget22.Devices.DigitalOutput import *
import time

def main():
digitalOutput0 = DigitalOutput()

digitalOutput0.setIsHubPortDevice(True)
digitalOutput0.setHubPort(0)

digitalOutput0.setChannelPersistence(True)

digitalOutput0.openWaitForAttachment(5000)

time.sleep(1)

digitalOutput0.setDutyCycle(1)

try:
input("Press Enter to Stop\n")
except (Exception, KeyboardInterrupt):
pass

digitalOutput0.close()

main()
</syntaxhighlight>
|-|
Javascript=<syntaxhighlight lang=javascript>
import * as phidget22 from 'phidget22';

const conn = new phidget22.NetworkConnection(5661, 'localhost');
await conn.connect();

const digitalOutput0 = new phidget22.DigitalOutput();

digitalOutput0.setIsHubPortDevice(true);
digitalOutput0.setHubPort(0);

digitalOutput0.channelPersistence = 1;

await digitalOutput0.open(5000);

await digitalOutput0.setDutyCycle(1);

setTimeout(async () => {
await digitalOutput0.close();
conn.close();
conn.delete();
process.exit();
}, 5000);
</syntaxhighlight>
|-|
Java=<syntaxhighlight lang=java>
import com.phidget22.*;
import java.util.Scanner; //Required for Text Input
import java.io.IOException;

public class Java_Example {

public static void main(String[] args) throws Exception {
DigitalOutput digitalOutput0 = new DigitalOutput();

digitalOutput0.setIsHubPortDevice(true);
digitalOutput0.setHubPort(0);

digitalOutput0.setChannelPersistence(true);

digitalOutput0.open(5000);

Thread.sleep(500);

digitalOutput0.setDutyCycle(1);

//Wait until Enter has been pressed before exiting
System.in.read();

digitalOutput0.close();
}
}
</syntaxhighlight>
|-|
C=<syntaxhighlight lang=c>
#include <phidget22.h>
#include <stdio.h>
#include <unistd.h>

int main() {
PhidgetDigitalOutputHandle digitalOutput0;

PhidgetDigitalOutput_create(&digitalOutput0);

Phidget_setIsHubPortDevice((PhidgetHandle)digitalOutput0, 1);
Phidget_setHubPort((PhidgetHandle)digitalOutput0, 0);

Phidget_setChannelPersistence((PhidgetHandle)digitalOutput0, 1);

Phidget_openWaitForAttachment((PhidgetHandle)digitalOutput0, 5000);

sleep(1);

PhidgetDigitalOutput_setDutyCycle(digitalOutput0, 1);

//Wait until Enter has been pressed before exiting
getchar();

Phidget_close((PhidgetHandle)digitalOutput0);

PhidgetDigitalOutput_delete(&digitalOutput0);
}
</syntaxhighlight>
</tabber>

Channel Persistence Guide - Revision history

Mparadis at 20:06, 16 September 2025