CODEWITHSUNDEEP
c#windowsubuntuusb
Tom Hosker
Tom Hosker

Reputation: 722

Creating a COM port out of a ttyUSB port in Ubuntu

The Question

I'm having to work with a rather awkward API at the moment which insists on me giving the address of a device, linked via USB port, in the form COM*. However, on the Ubuntu machine on which I'm working, and have to use, if I plug in this device it will automatically be assigned an address in the form /dev/ttyUSB*.

Given that I can't modify the source code of the API - which I would dearly like to do! - what is the least painful way getting the API to talk to said device?

Extra Detail

An example of how to use the API from the manual:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using com.caen.RFIDLibrary;

namespace ConsoleApplication1
{
  class Program
  {
    static void Main(string[] args)
    {
      CAENRFIDReader MyReader = new CAENRFIDReader();
      MyReader.Connect(CAENRFIDPort.CAENRFID_RS232, "COM3");
      CAENRFIDLogicalSource MySource = MyReader.GetSource("Source_0");
      CAENRFIDTag[] MyTags = MySource.InventoryTag();

      if (MyTags.Length > 0)
      {
        for (int i = 0; i < MyTags.Length; i++)
        {
          String s = BitConverter.ToString(MyTags[i].GetId());
          Console.WriteLine(s);
        }
      }
      Console.WriteLine("Press a key to end the program.");
      Console.ReadKey();
      MyReader.Disconnect();
    }
  }
}

The line MyReader.Connect(CAENRFIDPort.CAENRFID_RS232, "COM3"); is where I'm running into problems.

A little later in the manual, it states that the Connect method is to have two parameters:

ConType: The communication link to use for the connection.

Address: Depending on ConType parameter: IP address for TCP/IP communications ("xxx.xxx.xxx.xxx"), COM port for RS232 communications ("COMx"), an index for USB communications (not yet supported).

Bonus Question

The API in question seems to have been written on the assumption that it would be run on a Windows machine. (It's in C#.) The COM* format seems to be favoured - I'm happy to be corrected on this point - by Windows architectures, whereas Ubuntu seems to favour the ttyUSB* format. Assuming that I can funnel the data from my device from a ttyUSB* port to a COM* port, will the API actually be able to find said data? Or will it incorrectly follow the default Windows path?

Upvotes: 1

Views: 1145

Answers (1)

AnimeDev
AnimeDev

Reputation: 54

Given the new information i suspect you can just give the ttyUSB as the parameter, mono will handle the connection correctly. However the same caution for the line endings below still applies. You might also consider making the parameter a command-line parameter thus making your code run on any platform by being able to supply the COM/USB through the command line parameters. I see no other issues using this code. Did you try it yet?

PS: i think your confusion is actually the statement usb id's are not supported yet, i suspect that is because the library relies on a (text-based) serial connection wich are fundamentally different from direct USB connections (wich drivers normally handle) that handle the connection in a more direct way. The ttyUSB ports on linux however DO represent the (UART) serial connections the same way as windows COM-ports, these are not direct USB connections.

Some handy info about the differences: https://rfc1149.net/blog/2013/03/05/what-is-the-difference-between-devttyusbx-and-devttyacmx/

Old answer

I am assuming you run this program on Mono?

Mono expects the path to the port, so COM* will not do. You could try creating a symlink named COM* to the ttyUSB*. Preferrably located in the environment directory. Once you get them linked the program should see no difference. However line endings in the data/program might be different than on windows. If the device expects CRLF and the program uses Environment.NewLine you might get unexpected behaviour too. It might just be easier if you have the permission/rights to edit the assembly with recompilation tools.

Upvotes: 2

Related Questions