Difference between revisions of "Language - C"

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Line 25: Line 25:
  
 
== Windows ==
 
== Windows ==
{{Windows_Languages}}
+
===Install Phidget Drivers for Windows===
 +
Before getting started with the guides below, ensure you have the following components installed on your machine:
 +
 
 +
# You will need the [[OS_-_Windows#Quick_Downloads|Phidgets Windows Drivers]]
  
 
===Visual Studio===
 
===Visual Studio===
Line 47: Line 50:
 
[[Image: c_vs_output.PNG|link=|center]]
 
[[Image: c_vs_output.PNG|link=|center]]
  
 +
{{Edit_the_Examples}}
  
You should now have the example up and running for your device. Play around with the device and experiment with some of the functionality. When you are ready, the next step is configuring your project and writing your own code!
+
====Setting up a New Project====
 
+
====Configure Your Project====
+
 
When you are building a project from scratch, or adding Phidget functionality to an existing project, you'll need to configure your development environment to properly link the Phidget C library. To begin:
 
When you are building a project from scratch, or adding Phidget functionality to an existing project, you'll need to configure your development environment to properly link the Phidget C library. To begin:
  
Line 134: Line 136:
 
</syntaxhighlight>
 
</syntaxhighlight>
  
 +
{{Edit_the_Examples}}
  
You should now have the example up and running. When you are ready, the next step is configuring your project and writing your own code!
+
====Setting up a New Project====
 
+
When you are building a project from scratch, or adding Phidget functionality to an existing project, you'll need to configure your development environment to properly link the Phidget C library.
=====Configure Your Project=====
+
When you are building a project from scratch, or adding Phidget functionality to an exisiting project, you'll need to configure your development environment to properly link the Phidget C library.
+
  
 
To include the Phidget C library, add the following line to your code:
 
To include the Phidget C library, add the following line to your code:
Line 186: Line 187:
 
[[Image:C_codeblocks_run.png|link=|center]]
 
[[Image:C_codeblocks_run.png|link=|center]]
  
 +
{{Edit_the_Examples}}
  
You should now have the example up and running for your device. Play around with the device and experiment with some of the functionality. When you are ready, the next step is configuring your project and writing your own code!
+
====Setting up a New Project====
 
+
====Configure Your Project====
+
 
When you are building a project from scratch, or adding Phidget functionality to an existing project, you'll need to configure your development environment to properly link the Phidget C library.
 
When you are building a project from scratch, or adding Phidget functionality to an existing project, you'll need to configure your development environment to properly link the Phidget C library.
  
Line 204: Line 204:
  
 
==macOS==
 
==macOS==
{{macOS_Languages}}
+
===Install Phidget Drivers for macOS===
 +
Before getting started with the guides below, ensure you have the following components installed on your machine:
 +
 
 +
# You will need the [[OS_-_macOS#Quick_Downloads|Phidgets macOS Drivers]]
 +
 
 
===GCC===
 
===GCC===
 
====Use Our Examples====
 
====Use Our Examples====
Line 227: Line 231:
  
  
You should now have the example up and running for your device. Play around with the device and experiment with some of the functionality. When you are ready, the next step is configuring your project and writing your own code!
+
{{Edit_the_Examples}}
  
====Configure Your Project====
+
====Setting up a New Project====
 
When you are building a project from scratch, or adding Phidget functionality to an exisiting project, you'll need to configure your development environment to properly link the Phidget C library.
 
When you are building a project from scratch, or adding Phidget functionality to an exisiting project, you'll need to configure your development environment to properly link the Phidget C library.
  
Line 243: Line 247:
  
 
==Linux==
 
==Linux==
{{Linux_Languages}}
+
===Install Phidget Drivers for Linux===
 +
Before getting started with the guides below, ensure you have the following components installed on your machine:
 +
 
 +
# You will need the [[OS_-_Linux#Quick_Downloads|Phidgets Linux Drivers]]
 +
 
 
===GCC===
 
===GCC===
 
====Use Our Examples====
 
====Use Our Examples====
Line 268: Line 276:
  
  
You should now have the example up and running. When you are ready, the next step is configuring your project and writing your own code!
+
{{Edit_the_Examples}}
  
====Configure Your Project====
+
====Setting up a New Project====
 
When you are building a project from scratch, or adding Phidget functionality to an exisiting project, you'll need to configure your development environment to properly link the Phidget C library.
 
When you are building a project from scratch, or adding Phidget functionality to an exisiting project, you'll need to configure your development environment to properly link the Phidget C library.
  
Line 282: Line 290:
  
 
The project now has access to Phidgets. Next, view the [[#Write Code | write your own code]] section located below.
 
The project now has access to Phidgets. Next, view the [[#Write Code | write your own code]] section located below.
 +
 +
== Editing the Examples==
 +
To get our example code to run in a custom application, simply remove the calls to ''AskForDeviceParameters'' and ''PrintEventDescriptions'', and hard-code the addressing parameters for your application.
 +
 +
If you are unsure what values to use for the addressing parameters, check the [[Finding The Addressing Information]] page.
 +
 +
For instance:
 +
<syntaxhighlight lang=C>
 +
AskForDeviceParameters(&channelInfo, (PhidgetHandle)ch);
 +
 +
prc = Phidget_setDeviceSerialNumber((PhidgetHandle)ch, channelInfo.deviceSerialNumber);
 +
CheckError(prc, "Setting DeviceSerialNumber", &(PhidgetHandle)ch);
 +
 +
prc = Phidget_setHubPort((PhidgetHandle)ch, channelInfo.hubPort);
 +
CheckError(prc, "Setting HubPort", &(PhidgetHandle)ch);
 +
 +
prc = Phidget_setIsHubPortDevice((PhidgetHandle)ch, channelInfo.isHubPortDevice);
 +
CheckError(prc, "Setting IsHubPortDevice", &(PhidgetHandle)ch);
 +
   
 +
Phidget_setChannel((PhidgetHandle)ch, channelInfo.channel);
 +
CheckError(prc, "Setting Channel", &(PhidgetHandle)ch);
 +
 +
if (channelInfo.netInfo.isRemote) {
 +
    prc = Phidget_setIsRemote((PhidgetHandle)ch, channelInfo.netInfo.isRemote);
 +
    CheckError(prc, "Setting IsRemote", &(PhidgetHandle)ch);
 +
       
 +
    if (channelInfo.netInfo.serverDiscovery) {
 +
        prc = PhidgetNet_enableServerDiscovery(PHIDGETSERVER_DEVICEREMOTE);
 +
        CheckEnableServerDiscoveryError(prc, &(PhidgetHandle)ch);
 +
    } else {
 +
        prc = PhidgetNet_addServer("Server", channelInfo.netInfo.hostname,
 +
                    channelInfo.netInfo.port, channelInfo.netInfo.password, 0);
 +
        CheckError(prc, "Adding Server", &(PhidgetHandle)ch);
 +
    }
 +
}
 +
</syntaxhighlight>
 +
 +
Might become:
 +
 +
<syntaxhighlight lang=C>
 +
prc = Phidget_setDeviceSerialNumber((PhidgetHandle)ch, 370114);
 +
CheckError(prc, "Setting DeviceSerialNumber", &(PhidgetHandle)ch);
 +
 +
prc = Phidget_setHubPort((PhidgetHandle)ch, 2);
 +
CheckError(prc, "Setting HubPort", &(PhidgetHandle)ch);
 +
 +
prc = Phidget_setIsHubPortDevice((PhidgetHandle)ch, 1);
 +
CheckError(prc, "Setting IsHubPortDevice", &(PhidgetHandle)ch);
 +
</syntaxhighlight>
 +
 +
Notice that you can leave out any parameter not relevant to your application for simplicity.
 +
 +
You can then manipulate the rest of the code as your application requires. A more in-depth description of programming with Phidgets follows in the [[#Write Code| Write Code]] section.
  
 
==Write Code==
 
==Write Code==
You've followed the instructions above for your operating system and now have a working example. Next, we will show you how the example was created and how it works by getting into the code. When you are ready, head to our [[Phidget Programming Basics]] page. There you will find code examples written in C and you will be writing your own code in no time!
+
{{WriteCode_Intro|C}}
 +
 
 +
=== Step One: Create and Address===
 +
You will need to create your Phidget object in your code. For example, we can create a digital input object like this:
 +
<syntaxhighlight lang=c>
 +
PhidgetDigitalInputHandle ch;
 +
PhidgetDigitalInput_create(&ch);
 +
</syntaxhighlight>
 +
 
 +
Next, we can address which Phidget we want to connect to by setting parameters such as ''DeviceSerialNumber''.
 +
 
 +
<syntaxhighlight lang=C>
 +
Phidget_setDeviceSerialNumber((PhidgetHandle)ch, 496911);
 +
</syntaxhighlight>
 +
 
 +
Although we are not including it on this page, you should handle the return codes of all Phidget functions. Here is an example of the previous code with error handling:
 +
<syntaxhighlight lang=C>
 +
PhidgetReturnCode prc;
 +
PhidgetDigitalInputHandle ch;
 +
 
 +
prc = PhidgetDigitalInput_create(&ch);
 +
if (prc != EPHIDGET_OK) {
 +
fprintf(stderr, "Runtime Error -> Creating DigitalInput: \n\t");
 +
fprintf(stderr, "Code: 0x%x\n", error);
 +
return 1;
 +
}
 +
 
 +
prc = Phidget_setDeviceSerialNumber((PhidgetHandle)ch, 496911);
 +
if (prc != EPHIDGET_OK) {
 +
fprintf(stderr, "Runtime Error -> Setting DeviceSerialNumber: \n\t");
 +
fprintf(stderr, "Code: 0x%x\n", error);
 +
return 1;
 +
}
 +
</syntaxhighlight>
 +
 
 +
=== Step Two: Open and Wait for Attachment===
 +
 
 +
After we have specified which Phidget to connect to, we can open the Phidget object like this:
 +
<syntaxhighlight lang=C>
 +
Phidget_openWaitForAttachment((PhidgetHandle)ch, 5000);
 +
</syntaxhighlight>
 +
 
 +
To use a Phidget, it must be plugged in (attached). We can handle this by calling ''openWaitForAttachment'', which will block indefinitely until a connection is made, or until the timeout value is exceeded. Simply calling ''open'' does not guarantee you can use the Phidget immediately.
 +
 
 +
Alternately, you could verify the device is attached by using event driven programming and tracking the attach events.
 +
 
 +
To use events to handle attachments, we have to modify our code slightly:
 +
<syntaxhighlight lang=C>
 +
PhidgetDigitalInputHandle ch;
 +
PhidgetDigitalInput_create(&ch);
 +
 
 +
Phidget_setOnAttachHandler((PhidgetHandle)ch, onAttachHandler, null);
 +
 
 +
Phidget_openWaitForAttachment((PhidgetHandle)ch, 5000);
 +
</syntaxhighlight>
 +
 
 +
Next, we have to declare the function that will be called when an attach event is fired - in this case the function ''onAttachHandler'' will be called:
 +
<syntaxhighlight lang=C>
 +
static void CCONV onAttachHandler(PhidgetHandle ph, void *ctx) {
 +
    printf("Phidget attached!\n");
 +
}
 +
</syntaxhighlight>
 +
 
 +
We recommend using this attach handler to set any initialization parameters for the channel such as DataInterval and ChangeTrigger from within the AttachHandler, so the parameters are set as soon as the device becomes available.
 +
 
 +
=== Step Three: Do Things with the Phidget ===
 +
We recommend the use of event driven programming when working with Phidgets. In a similar way to handling an attach event as described above, we can also add an event handler for a state change event:
 +
<syntaxhighlight lang=C>
 +
PhidgetDigitalInputHandle ch;
 +
PhidgetDigitalInput_create(&ch);
 +
 
 +
Phidget_setOnAttachHandler((PhidgetHandle)ch, onAttachHandler, null);
 +
PhidgetDigitalInput_setOnStateChangeHandler(ch, onStateChangeHandler, null);
 +
 
 +
Phidget_openWaitForAttachment((PhidgetHandle)ch, 5000);
 +
</syntaxhighlight>
 +
 
 +
This code will connect a function to an event. In this case, the ''onStateChangeHandler'' function will be called when there has been a change to the channel's input. Next, we need to create the ''onStateChangeHandler'' function:
 +
<syntaxhighlight lang=C>
 +
static void CCONV onStateChangeHandler(PhidgetDigitalInputHandle ph, void *ctx, int state) {
 +
    printf("State: %d\n", state);
 +
}
 +
</syntaxhighlight>
 +
 
 +
If you are using multiple Phidgets in your program, check out our page on [[Using_Multiple_Phidgets]] for information on how to properly address them and use them in events.
 +
 
 +
If events do not suit your needs, you can also poll the device directly for data using code like this:
 +
<syntaxhighlight lang=C>
 +
int state;
 +
PhidgetDigitalInput_getState(ch, &state);
 +
printf("State: %d\n", state);
 +
</syntaxhighlight>
 +
 
 +
'''Important Note:''' There will be a period of time between the attachment of a Phidget sensor and the availability of the first data from the device. Any attempts to get this data before it is ready will result in an error code, and a specific nonsensical result. See more information on this on our page for [[Unknown Values]].
 +
 
 +
====Enumerations====
 +
 
 +
Some Phidget devices have functions that deal with specific predefined values called enumerations. Enumerations commonly provide readable names to a set of numbered options.
 +
 
 +
Enumerations with Phidgets in C will take the form of '''ENUMERATION_NAME'''.
 +
 
 +
For example, specifying a SensorType to use the 1142 for a voltage input would look like:
 +
<syntaxhighlight lang=C>
 +
SENSOR_TYPE_1142
 +
</syntaxhighlight>
 +
and specifying a K-Type thermocouple for a temperature sensor would be:
 +
<syntaxhighlight lang=C>
 +
THERMOCOUPLE_TYPE_K
 +
</syntaxhighlight>
 +
The Phidget error code for timing out could be specified as:
 +
<syntaxhighlight lang=C>
 +
EPHIDGET_TIMEOUT
 +
</syntaxhighlight>
 +
 
 +
You can find the Enumeration Type under the ''Enumerations'' section of the {{Phidget22API}} for your device, and the Enumeration Name in the drop-down list within.
 +
 
 +
=== Step Four: Close and Delete ===
 +
At the end of your program, be sure to close and delete your device:
 +
<syntaxhighlight lang=C>
 +
Phidget_close((PhidgetHandle)ch);
 +
PhidgetDigitalInput_delete(&ch);
 +
</syntaxhighlight>
  
 
== Further Reading ==
 
== Further Reading ==

Revision as of 16:36, 20 June 2018

Quick Downloads

Documentation

Example Code

Libraries

Getting Started with C

Welcome to using Phidgets with C! By using C, you will have access to the complete Phidget22 API, including events. Example code is also provided for each Phidget channel class.

If developing for Windows, keep reading; otherwise, select an operating system:

Windows

Install Phidget Drivers for Windows

Before getting started with the guides below, ensure you have the following components installed on your machine:

  1. You will need the Phidgets Windows Drivers

Visual Studio

Use Our Examples

One of the best ways to start programming with Phidgets is to use our example code as a guide. In order to run the examples, you will need to download and install Microsoft Visual Studio.


Now that you have Microsoft Visual Studio installed, select an example that will work with your Phidget:


Open the example project and start the example by pressing the Local Windows Debugger button:


C vs run.png


The application will open the Phidget, list basic information about the Phidget, and demonstrate the Phidget's functionality. Here is an example of an Accelerometer channel on a Spatial Phidget:


C vs output.PNG

You should now have the example up and running for your device. Your next step is to look at the Editing the Examples section below for information about the example and important concepts for programming Phidgets. This would be a good time to play around with the device and experiment with some of its functionality.

Setting up a New Project

When you are building a project from scratch, or adding Phidget functionality to an existing project, you'll need to configure your development environment to properly link the Phidget C library. To begin:


Create a new Win32 Console application:

C vs newproject.PNG


Select an empty project and finish:

C vs emptyproject.PNG


If you are using a 64-bit machine, select x64, otherwise, keep x86:

C vs configuration.png


Next, add a new item to your source folder:

C vs additem.png


Give the source file a descriptive name and continue:

C vs addsource.PNG


Access the project's properties:

C vs propertie.png


Next, navigate to Configuration Properties -> C/C++ -> General and add the following line to the additional include directories:

  • C:\Program Files\Phidgets\Phidget22


C vs additionalinclude.png


Navigate to Configuration Properties -> Linker -> Input and add the following line to the additional dependencies:

  • C:\Program Files\Phidgets\Phidget22\phidget22.lib


C vs additionadepend.png

Finally, include the Phidget library in your code, and any other header files:

#include <phidget22.h>
C vs finished.PNG


Success! The project now has access to Phidgets. Next, view the write your own code section located below.

GCC

Cygwin/MinGW

Use Our Examples

One of the best ways to start programming with Phidgets is to use our example code as a guide. In order to run the examples, you will need to download and install either MinGW or Cygwin.


Now that you have either MinGW or Cygwin installed, select an example that will work with your Phidget:


If you are using Cygwin, navigate to the folder where the example is and open the command prompt. Enter the following command to compile the example:

gcc example.c -o example -I"/cygdrive/c/Program Files/Phidgets/Phidget22" -L"/cygdrive/c/Program Files/Phidgets/Phidget22/x86" -lphidget22


If you are using MinGW, navigate to the folder where the example is and open the command prompt. Enter the following command to compile the example:

gcc example.c -o example -I"C:/Program Files/Phidgets/Phidget22" -L"C:/Program Files/Phidgets/Phidget22/x86" -lphidget22

After running the commands above for either Cygwin or MinGW, an executable file called example.exe will be created. Enter the following command to run the example:

example.exe

You should now have the example up and running for your device. Your next step is to look at the Editing the Examples section below for information about the example and important concepts for programming Phidgets. This would be a good time to play around with the device and experiment with some of its functionality.

Setting up a New Project

When you are building a project from scratch, or adding Phidget functionality to an existing project, you'll need to configure your development environment to properly link the Phidget C library.

To include the Phidget C library, add the following line to your code:

#include <phidget22.h>

You can now compile the file as shown in the previous section.


The project now has access to Phidgets. Next, view the write your own code section located below.

Code::Blocks

Use Our Examples

One of the best ways to start programming with Phidgets is to use our example code as a guide. In order to run the examples, you will need to download and install Code::Blocks.


Now that you have Code::Blocks installed, select an example that will work with your Phidget:


Open the example in Code::Blocks (you do not need to create a new project) and navigate to Settings -> Compiler... as shown in the image below:

C codeblocks settings.png


From the Global compiler settings screen, navigate to Search directories -> Compiler and add the following directory:

  • C:\Program Files\Phidgets\Phidget22
C codeblocks compiler.PNG


Next, select Search directories -> Linker and add the following directory:

  • C:\Program Files\Phidgets\Phidget22\x86
C codeblocks linker.PNG


Finally, from the Global compiler settings screen, navigate to Linker settings and add the following line:

  • phidget22
C codeblocks libraries.PNG


You can now build and run the example:

C codeblocks run.png

You should now have the example up and running for your device. Your next step is to look at the Editing the Examples section below for information about the example and important concepts for programming Phidgets. This would be a good time to play around with the device and experiment with some of its functionality.

Setting up a New Project

When you are building a project from scratch, or adding Phidget functionality to an existing project, you'll need to configure your development environment to properly link the Phidget C library.


To include the Phidget C library, add the following line to your code:

#include <phidget22.h>

You can now compile the file as shown in the previous section.


The project now has access to Phidgets. Next, view the write your own code section located below.

macOS

Install Phidget Drivers for macOS

Before getting started with the guides below, ensure you have the following components installed on your machine:

  1. You will need the Phidgets macOS Drivers

GCC

Use Our Examples

One of the best ways to start programming with Phidgets is to use our example code as a guide. You likely have gcc installed on your macOS machine already, but if not, you can easily get it by downloading Xcode.

Next, select an example that will work with your Phidget:


To compile the example program, enter the following command in the terminal:

gcc example.c -o example -F /Library/Frameworks -framework Phidget22 -I /Library/Frameworks/Phidget22.framework/Headers

Finally, run the program by entering the following command in the terminal:

./example


C mac gcc.png


You should now have the example up and running for your device. Your next step is to look at the Editing the Examples section below for information about the example and important concepts for programming Phidgets. This would be a good time to play around with the device and experiment with some of its functionality.

Setting up a New Project

When you are building a project from scratch, or adding Phidget functionality to an exisiting project, you'll need to configure your development environment to properly link the Phidget C library.

To include the Phidget C library, simply add the following line to your code:

#include <phidget22.h>

You can now compile the file as shown in the previous section.


The project now has access to Phidgets. Next, view the write your own code section located below.

Linux

Install Phidget Drivers for Linux

Before getting started with the guides below, ensure you have the following components installed on your machine:

  1. You will need the Phidgets Linux Drivers

GCC

Use Our Examples

One of the best ways to start programming with Phidgets is to use our example code as a guide. You likely have gcc installed on your Linux machine already, but if not, you can easily get it by entering the following command in the terminal:

apt-get install gcc


Next, select an example that will work with your Phidget:


To compile the example, enter the following command in the terminal:

gcc example.c -o example -lphidget22

After compiling, you can run the program by entering the following command in the terminal:

./example


You should now have the example up and running for your device. Your next step is to look at the Editing the Examples section below for information about the example and important concepts for programming Phidgets. This would be a good time to play around with the device and experiment with some of its functionality.

Setting up a New Project

When you are building a project from scratch, or adding Phidget functionality to an exisiting project, you'll need to configure your development environment to properly link the Phidget C library.

To include the Phidget C library, simply add the following line to your code:

#include <phidget22.h>

You can now compile the file as shown in the previous section.


The project now has access to Phidgets. Next, view the write your own code section located below.

Editing the Examples

To get our example code to run in a custom application, simply remove the calls to AskForDeviceParameters and PrintEventDescriptions, and hard-code the addressing parameters for your application.

If you are unsure what values to use for the addressing parameters, check the Finding The Addressing Information page.

For instance:

AskForDeviceParameters(&channelInfo, (PhidgetHandle)ch);

prc = Phidget_setDeviceSerialNumber((PhidgetHandle)ch, channelInfo.deviceSerialNumber);
CheckError(prc, "Setting DeviceSerialNumber", &(PhidgetHandle)ch);

prc = Phidget_setHubPort((PhidgetHandle)ch, channelInfo.hubPort);
CheckError(prc, "Setting HubPort", &(PhidgetHandle)ch);

prc = Phidget_setIsHubPortDevice((PhidgetHandle)ch, channelInfo.isHubPortDevice);
CheckError(prc, "Setting IsHubPortDevice", &(PhidgetHandle)ch);
    
Phidget_setChannel((PhidgetHandle)ch, channelInfo.channel);
CheckError(prc, "Setting Channel", &(PhidgetHandle)ch);

if (channelInfo.netInfo.isRemote) {
    prc = Phidget_setIsRemote((PhidgetHandle)ch, channelInfo.netInfo.isRemote);
    CheckError(prc, "Setting IsRemote", &(PhidgetHandle)ch);
        
    if (channelInfo.netInfo.serverDiscovery) {
        prc = PhidgetNet_enableServerDiscovery(PHIDGETSERVER_DEVICEREMOTE);
        CheckEnableServerDiscoveryError(prc, &(PhidgetHandle)ch);
    } else {
        prc = PhidgetNet_addServer("Server", channelInfo.netInfo.hostname,
                    channelInfo.netInfo.port, channelInfo.netInfo.password, 0);
        CheckError(prc, "Adding Server", &(PhidgetHandle)ch);
    }
}

Might become:

prc = Phidget_setDeviceSerialNumber((PhidgetHandle)ch, 370114);
CheckError(prc, "Setting DeviceSerialNumber", &(PhidgetHandle)ch);

prc = Phidget_setHubPort((PhidgetHandle)ch, 2);
CheckError(prc, "Setting HubPort", &(PhidgetHandle)ch);

prc = Phidget_setIsHubPortDevice((PhidgetHandle)ch, 1);
CheckError(prc, "Setting IsHubPortDevice", &(PhidgetHandle)ch);

Notice that you can leave out any parameter not relevant to your application for simplicity.

You can then manipulate the rest of the code as your application requires. A more in-depth description of programming with Phidgets follows in the Write Code section.

Write Code

By following the instructions for your operating system and compiler above, you now have working examples and a project that is configured. This teaching section will help you understand how the examples were written so you can start writing your own code.


Remember: your main reference for writing C code will be the Phidget22 API Manual and the example code.

Step One: Create and Address

You will need to create your Phidget object in your code. For example, we can create a digital input object like this:

PhidgetDigitalInputHandle ch;
PhidgetDigitalInput_create(&ch);

Next, we can address which Phidget we want to connect to by setting parameters such as DeviceSerialNumber.

Phidget_setDeviceSerialNumber((PhidgetHandle)ch, 496911);

Although we are not including it on this page, you should handle the return codes of all Phidget functions. Here is an example of the previous code with error handling:

PhidgetReturnCode prc;
PhidgetDigitalInputHandle ch;

prc = PhidgetDigitalInput_create(&ch);
if (prc != EPHIDGET_OK) {
	fprintf(stderr, "Runtime Error -> Creating DigitalInput: \n\t");
	fprintf(stderr, "Code: 0x%x\n", error);
	return 1;
}

prc = Phidget_setDeviceSerialNumber((PhidgetHandle)ch, 496911);
if (prc != EPHIDGET_OK) {
	fprintf(stderr, "Runtime Error -> Setting DeviceSerialNumber: \n\t");
	fprintf(stderr, "Code: 0x%x\n", error);
	return 1;
}

Step Two: Open and Wait for Attachment

After we have specified which Phidget to connect to, we can open the Phidget object like this:

Phidget_openWaitForAttachment((PhidgetHandle)ch, 5000);

To use a Phidget, it must be plugged in (attached). We can handle this by calling openWaitForAttachment, which will block indefinitely until a connection is made, or until the timeout value is exceeded. Simply calling open does not guarantee you can use the Phidget immediately.

Alternately, you could verify the device is attached by using event driven programming and tracking the attach events.

To use events to handle attachments, we have to modify our code slightly:

PhidgetDigitalInputHandle ch;
PhidgetDigitalInput_create(&ch);

Phidget_setOnAttachHandler((PhidgetHandle)ch, onAttachHandler, null);

Phidget_openWaitForAttachment((PhidgetHandle)ch, 5000);

Next, we have to declare the function that will be called when an attach event is fired - in this case the function onAttachHandler will be called:

static void CCONV onAttachHandler(PhidgetHandle ph, void *ctx) {
    printf("Phidget attached!\n");
}

We recommend using this attach handler to set any initialization parameters for the channel such as DataInterval and ChangeTrigger from within the AttachHandler, so the parameters are set as soon as the device becomes available.

Step Three: Do Things with the Phidget

We recommend the use of event driven programming when working with Phidgets. In a similar way to handling an attach event as described above, we can also add an event handler for a state change event:

PhidgetDigitalInputHandle ch;
PhidgetDigitalInput_create(&ch);

Phidget_setOnAttachHandler((PhidgetHandle)ch, onAttachHandler, null);
PhidgetDigitalInput_setOnStateChangeHandler(ch, onStateChangeHandler, null);

Phidget_openWaitForAttachment((PhidgetHandle)ch, 5000);

This code will connect a function to an event. In this case, the onStateChangeHandler function will be called when there has been a change to the channel's input. Next, we need to create the onStateChangeHandler function:

static void CCONV onStateChangeHandler(PhidgetDigitalInputHandle ph, void *ctx, int state) {
    printf("State: %d\n", state);
}

If you are using multiple Phidgets in your program, check out our page on Using_Multiple_Phidgets for information on how to properly address them and use them in events.

If events do not suit your needs, you can also poll the device directly for data using code like this:

int state;
PhidgetDigitalInput_getState(ch, &state);
printf("State: %d\n", state);

Important Note: There will be a period of time between the attachment of a Phidget sensor and the availability of the first data from the device. Any attempts to get this data before it is ready will result in an error code, and a specific nonsensical result. See more information on this on our page for Unknown Values.

Enumerations

Some Phidget devices have functions that deal with specific predefined values called enumerations. Enumerations commonly provide readable names to a set of numbered options.

Enumerations with Phidgets in C will take the form of ENUMERATION_NAME.

For example, specifying a SensorType to use the 1142 for a voltage input would look like:

SENSOR_TYPE_1142

and specifying a K-Type thermocouple for a temperature sensor would be:

THERMOCOUPLE_TYPE_K

The Phidget error code for timing out could be specified as:

EPHIDGET_TIMEOUT

You can find the Enumeration Type under the Enumerations section of the Phidget22 API for your device, and the Enumeration Name in the drop-down list within.

Step Four: Close and Delete

At the end of your program, be sure to close and delete your device:

Phidget_close((PhidgetHandle)ch);
PhidgetDigitalInput_delete(&ch);

Further Reading

Phidget Programming Basics - Here you can find the basic concepts to help you get started with making your own programs that use Phidgets.

Data Interval/Change Trigger - Learn about these two properties that control how much data comes in from your sensors.

Using Multiple Phidgets - It can be difficult to figure out how to use more than one Phidget in your program. This page will guide you through the steps.

Polling vs. Events - Your program can gather data in either a polling-driven or event-driven manner. Learn the difference to determine which is best for your application.

Logging, Exceptions, and Errors - Learn about all the tools you can use to debug your program.

Phidget Network Server - Phidgets can be controlled and communicated with over your network- either wirelessly or over ethernet.