I have a sketch running on the Arduino which sends text over the serial port to the PC and responds to commands from the PC

Using a Uno or Leonardo the text is displayed correctly in terminal or monitor window (eg built in serial monitor or TeraTerm)

However using a VB.NET (or C#) Windows forms application nothing is recieved or can be sent to the serial port if a Leonardo is used, but it all works fine with a Uno (exactly the same code at both ends in both cases).

The VB programme scans the available serial ports and finds the one with "Arduino Leonardo" name ok, it opens ok, but the programme can't write to the port (timeout error) and nothing is recieved from the port. Works fine with a Uno.

This is probably not a Visual Micro problem; it appears to be a Visual Studio problem. I just wondered if anyone else has encountered it and if there is a fix/workaround.

When the Leo is connected Windows device manager is reporting it as a keyboard and a mouse and a gamepad and a serial port - are the other functions interferring? But only for an app compiled in Visual studio!
Puzzled of Plymouth

Visual Micro (inside Visual Studio) is used to compile and upload the sketch to the Arduino.

The problem is with the application that then communiates with the Arduino running the sketch over the USB virtual serial port. A Uno works fine. A Leo only works with a teminal emulator (eg TeraTerm). The application sees the port but can't write or read to it. The application works fine for a Uno (or a Mega2560)

As I said this is 99% certain not a VM problem, more a general enquiry whether anyone else has this problem with a Windows Forms application produced in Visual Studio.

It looks like a problem in .NET v4.5 Framework

Nope, none of those I'm afraid.
I now have the minimal sketch - ouputs a count every half second - and a minimal windows app - opens a serial port and display numbers recieved.
Uno works, Leo port opens ok but nothing recieved.
In a terminal both Leo and Uno work - numbers dislayed

Attached doc has the minimal sketch and form code if anyone is interested in spotting the error.

(no it doesn't, website error - Could not open a new file on the server, check the paths and chmods D:/Domains/visualmicro.com/www/public_html/yabbfiles/Attachments)

Amazingly in the meantime (5mins) I have stumbled upon the cause of the problem.

For Leonardo when opening the COMport you have to set both DtrEnable and RtsEnable properties true. 

Unlike the Uno or Mega2560. The default is that they are false, and many code examples out there set them false explicitly.

Hope this saves someone else some headbanging.

RogerCO

Hi both,

You will see that in the Visual Micro serial monitor the default sets DTR and RTS to true. THis is the case for all Arduino boards. In fact I think it is only the ESP boards that do not use this system but they have a config setting to tell us not to enable DTR.

The only time you should see an external code example that does not enable DTR is when triggering the bootloader for certain boards that require a 1200 baud connect to reset the chip and put it on programming mode. The Leonardo is a board that uses this special reset and those are the code examples you might have seen, all relate to upload.

Your own VB programs will not want to upload, instead just use the Serial to the board. In this case you should always set the DTR for all Arduino boards.