SendMessage.cs

// This tutorial walks you through how to open a channel and send a CAN message on it.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

using Ôƺ£ÓÎÏ·.CanLib;

namespace SendMessage
{
    class Program
    {
        static void Main(string[] args)
        {
            // Holds a handle to the CAN channel
            int handle;

            // Status returned by the Canlib calls
            Canlib.canStatus status;

            // The CANlib channel number we would like to use
            int channelNumber = 0;

            // The msg will be the body of the message we send on the CAN bus.
            byte[] msg = {0, 1, 2, 3, 4, 5, 6, 7};

            Console.OutputEncoding = System.Text.Encoding.UTF8;

            Console.WriteLine("Initializing Canlib");

            // Initialize the Canlib library with a call to
            // Canlib.initializeLibrary(). This always needs to be done before
            // doing anything with the library.
            Canlib.canInitializeLibrary();

            Console.WriteLine("Opening channel {0}", channelNumber);

            // Next, we open up the channel and receive a handle to
            // it. Depending on what devices you have connected to your
            // computer, you might want to change the channel number. The
            // canOPEN_ACCEPT_VIRTUAL flag means that it is ok to open the
            // selected channel, even if it is on a virtual device.
            handle = Canlib.canOpenChannel(channelNumber, Canlib.canOPEN_ACCEPT_VIRTUAL);
            CheckStatus((Canlib.canStatus)handle, "canOpenChannel");

            Console.WriteLine("Setting channel bitrate");

            // Once we have successfully opened a channel, we need to set its bitrate. We
            // do this using canSetBusParams. CANlib provides a set of predefined bus parameter
            // settings in the form of canBITRATE_XXX constants. For other desired bus speeds
            // bus paramters have to be set manually.
            // See CANlib documentation for more information on parameter settings.
            status = Canlib.canSetBusParams(handle, Canlib.canBITRATE_250K, 0, 0, 0, 0);
            CheckStatus(status, "canSetBusParams");

            Console.WriteLine("Going on bus");

            // Next, take the channel on bus using the canBusOn method. This
            // needs to be done before we can send a message.
            status = Canlib.canBusOn(handle);
            CheckStatus(status, "canBusOn");

            Console.WriteLine("Writing a message to the channel");

            // We send the message using canWrite. This method takes five
            // parameters: the channel handle, the message identifier, the
            // message body, the message length (in bytes) and optional flags.
            status = Canlib.canWrite(handle, 123, msg, 8, 0);
            CheckStatus(status, "canWrite");

            Console.WriteLine("Waiting for the message to be transmitted");

            // After sending, we wait for at most 1000 ms for the message to be sent, using
            // canWriteSync.
            status = Canlib.canWriteSync(handle, 1000);
            CheckStatus(status, "canWriteSync");

            Console.WriteLine("Going off bus");

            // Once we are done using the channel, we go off bus using the
            // canBusOff method. It take the handle as the only argument.
            status = Canlib.canBusOff(handle);
            CheckStatus(status, "canBusOff");

            Console.WriteLine("Closing channel {0}", channelNumber);

            // We also close the channel using the canCloseChannel method,
            // which take the handle as the only argument.
            status = Canlib.canClose(handle);
            CheckStatus(status, "canClose");

            // Wait for the user to press a key before exiting, in case the
            // console closes automatically on exit.
            Console.WriteLine("Press any key to exit");
            Console.ReadKey();
        }


        // The check method takes a canStatus (which is an enumerable) and the method
        // name as a string argument. If the status is an error code, it will print it.
        // Most Canlib method return a status, and checking it with a method like this
        // is a useful practice to avoid code duplication.
        private static void CheckStatus(Canlib.canStatus status, string method)
        {
            if (status < 0)
            {
                string errorText;
                Canlib.canGetErrorText(status, out errorText);
                Console.WriteLine(method + " failed: " + errorText);
            }
        }
    }
}

/*
 Exercises:
  - The canWriteWait method combines canWrite with canWriteSync. Try it out.

  - Use some other program (such as Ôƺ£ÓÎÏ· CanKing) to listen for messages on a
    channel connected to the one used in the program. Make sure to use the same
    bitrate.

  - Change the fourth parameter in the call to canWrite to 4. What happens to
    the message on the receiving side?

  - Change the message identifier to something large, like 10000. What happens
    on the receiving side? Then, change the fifth parameter to
    Canlib.canMSG_EXT. What happens now?
*/