I've been working with the SerialPort class a lot lately. Currently I'm trying to figure out the proper way to check if a device is connected to the comm port my application uses. Is there any proper way to check if a device is connected to the comm port? My current method is as follows:

It works but I feel it's a little hacky and unreliable. I can keep it if need be but I'd like it if there's a proper alternative to doing this.

Edit: I actually have to set the tick value to about 10,000 to ensure it's reliable. Otherwise I fail to receive data on occasion. Even setting it to 1000 or 5000 is unreliable. Even then, it's not guaranteed to be reliable across multiple machines.

3 Answers

I too need to work with serial ports, and believe me they are a pain.My method to check if a device is connected usually revolves around issuing a polling command.While you method may work, I cant help but be reluctant to use a while loop when an event will suffice.

The .NET serial port class offers some useful events:

Serial.DataReceivedSerial.ErrorReceived and Serial.Write

Usually I would issue a polling command at a specified interval to ensure the device is connected.When the device responds it will fire the DataReceived event, and you can deal with the response accordingly (along with any other neccessary data). This can be used in conjunction with a simple Timer or incremented variable to time the response. Note you will need to set the ReadTimeout and WriteTimeout value appropriately. This, along with the ReadExisting and/or ReadLine method may be of use in your DataReceived event handler.

So, to summarize, (in pseudo code)

Unfortunately with serial ports, there's no proper way to determine if a certain device is connected. You could write a magic message that only your device would respond correctly to, but as described in this answer, this method could cause problems for other connected devices.

Ultimately, you just have to depend on the user selecting the correct port.

Also, if you happen to lose connection to the device, you would only know when you fail to read/write to it. In this case, just throw a LostConnection event.

I would agree that is a hacky because any device could be connected and sending '>'; but that doesn't mean its your device.

Instead, be dynamic and use something like SerialPort.GetPortNames and WMI Queries to interrogate the devices plugged into the COM ports.

You could use this example as a starting point.

After reading documentation and examples, you should be able to create a list of all device information that registers drivers on the computer and their connected COM port.

Edit:

Since the device doesn't register itself, consider looking at the product drivers for Visual Studio that might make your job a lot easier. Musik barat lama mp3.

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I'm about to start developing a small app (C#) that communicates with a PLC and a testing unit via Serial Ports - this is my first venture into this area.

In essence, I am going to send the PLC a signal to start an operation, and then I am going to wait for the result of that operation from the test unit (which will be independently communicating with the PLC) to return a ASCII string.

Depending on the content of that string, I may want to listen to a signal from the PLC..

It's all new to me, so at the moment, I'm just researching System.IO.Ports.SerialPort; digression: are there third part products out there than simplify interaction with the Serial Port, or are the built-in classes as good as you will get? I'm thinking of ease of use as opposed to better features.

However, it will be a few weeks before the hardware is available for development and testing, so I was wondering how I could simulate communication to/from the serial port so that I can start developing my app?

[I don't yet know how the PLC and the PC are due to communicate - I understand it will be binary rather than text, but at the moment, that is all I know.]

6 Answers

Abstract away your serial port comms behind an interface so that you can code your app against the interface and then test with a 'fake' implementation. When you've got the hardware for the real thing, you can code up the 'real' implementation of the interface and swap out the fake one.

So for example, you'd have an interface

and you'd code your app against that interface using a fake implementation:

Hope that helps!

There are two pieces of software that I have found invaluable while doing serial port work.

Free Serial Port Monitor

Despite the cheesy name, it is actually quite useful. Note that you should have it stop listening to your port if you go to unplug a USB-to-Serial converter. Otherwise it can crash (well.. wait indefinitely on exit, which is annoying). It doesn't have to put itself in the middle of a serial connection to sniff data. It monitors the IO using the Win32 API.

Franson Serial Port Tools

Or. any loopback software really. There are lots out there. This allows you to send data and receive it within software. If you end up doing any GPS work, Franson also has a nice GPS simulator so you don't have to sit outside the whole time to debug code.

Finally, if you have had enough with the built-in serial class and its horrendous shortcomings, then you need a replacement, and going straight to the Win32 API will take forever.

CommStudio

I have found CommStudio to be absolutely rock solid. Quite frankly, after spending 5 months researching and buying other options, it is the only one that works perfectly with removable USB adapters. All of the other solutions have issues when the device is plugged back in. You can download their free 'Express' version here: http://www.componentsource.com/products/commstudio/downloads.html?rv=42917

There is another resource out there that emulates serial ports for windows if anyone else is still looking for decent serial debugging tools.

The 32-bit version is free and seems pretty decent. It's called Virtual Serial Ports Emulator.

I like David's answer above but if your looking to do integration tests and actually test your serial port communication I have used and application called ViN soft virtual serial cable in the past to basically create 2 serial ports on your machine that are connected by a virtual cable.

Also if you have a serial port on your development machine you could use it to connect to another machine that has a serial port and write an application that will basically simulate the communication of the PLC.

I would prefer to use a combination of both David's method and this method to ensure proper testing.

I have wrote an article on this topic using Virtual Serial Port Driver 9.0 standard using Microsoft SerialPort Class (Sytem.IO.Ports), it is of course possible to use any other comm port tool.

In the software I create 2 virtual ports COM1 and COM2.

I use COM1 to emulate as data sender.

I use COM2 to receive what ever being send from COM1.

This is helpful if you are developing Embedded or IoT solution.

Emulator (in this example as random accelerometer)

And my data receiver is almost similar

Disclaimer: the link of this guideline refer to my personal web site.

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