lunoptics.TeensySharp 2.0.0

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Additional Details

Not compatible to recent releases of Teensyduino please use lunOptics.libTeensySharp instead

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Install-Package lunoptics.TeensySharp -Version 2.0.0
dotnet add package lunoptics.TeensySharp --version 2.0.0
<PackageReference Include="lunoptics.TeensySharp" Version="2.0.0" />
For projects that support PackageReference, copy this XML node into the project file to reference the package.
paket add lunoptics.TeensySharp --version 2.0.0
The NuGet Team does not provide support for this client. Please contact its maintainers for support.
#r "nuget: lunoptics.TeensySharp, 2.0.0"
#r directive can be used in F# Interactive, C# scripting and .NET Interactive. Copy this into the interactive tool or source code of the script to reference the package.
// Install lunoptics.TeensySharp as a Cake Addin
#addin nuget:?package=lunoptics.TeensySharp&version=2.0.0

// Install lunoptics.TeensySharp as a Cake Tool
#tool nuget:?package=lunoptics.TeensySharp&version=2.0.0
The NuGet Team does not provide support for this client. Please contact its maintainers for support.


This library provides some helper classes for C# Windows applications which communicate to PJRC Teensy boards. Currently the following common tasks are handled:

  • Finding all Teensies on the USB tree (get a list with entries for each found board containing its serialnumber and the name of the COM port to which it is connected)
  • Provide information when a Teensy is connected or removed from the USB Tree
  • Uploading of firmware (ihex files) from within the user application.


TeensySharp was developed using Microsoft VisualStudio 2017 Community Edition. The correspondig .sln file is contained in the repo. The library depends on the HIDLibrary from Mike O'Brian which can be found here: and on MoreLinq ( Both are available as NuGet packages. A download of the binaries from NuGet should start automatically when you build the solution.


Finding Connected Teensies

class TeensyWatcher

To obtain a list of all currently connected Teensies you can do the following:

var Watcher = new TeensyWatcher(); 
foreach (USB_Device Teensy in Watcher.ConnectedDevices)
    Console.WriteLine("Serialnumber {0}", Teensy.Serialnumber);

If you are interested in all boards running in USB-Serial mode you can write

var Watcher = new TeensyWatcher(); 
foreach (USB_Device Teensy in Watcher.ConnectedDevices.Where(t=>t.Type == USB_Device.type.UsbSerial))
    Console.WriteLine("Serialnumber {0}, on {1}", Teensy.Serialnumber, Teensy.Port);

The string Teensy.Port can then be used to construct a SerialPort object without having your users to guess which port number Windows assigned to your device today.

In case you are looking for a board with a running bootloader and serialnumber 8324210

var Watcher = new TeensyWatcher(); 
var Teensy = Watcher.ConnectedDevices.FirstOrDefault(t=>(t.Serialnumber==8324210 && t.Type==USB_Device.type.HalfKay ));

The list of connected boards will be updated in the background whenever a Teensy is connected or removed. If you need a notification when the list changes you also can attach an eventhandler to the watcher:

var Watcher = new TeensyWatcher(); 
Watcher.ConnectionChanged += ConnectedTeensiesChanged;
void ConnectedTeensiesChanged(object sender, ConnectionChangedEventArgs e)
    string Port = e.changedDevice.Port;
    string SN = e.changedDevice.Serialnumber;

The repo contains a simple console application (TeensyWacherConsole) which demonstrates the use of the TeensyWatcher class and the eventhandler in more detail.

Firmware Uploading

class SharpHexParser

The static SharpHexParser class is used to parse an Intel HEX stream and copy the result,i.e. the firmware into a flash image (which is a simple byte array). To generate an empty flash image with the correct size you can call a member of the SharpUploader as shown in the following code snippet. (PJRC_Board is an enum containing definitions for all supported PJRC Teensy Boards)

var Board = PJRC_Board.Teensy_31; 
var FlashImage = SharpUploader.GetEmptyFlashImage(Board);
SharpHexParser.ParseStream(File.OpenText("firmware.hex"), FlashImage);

The flash image now contains the bytes to be uploaded to the board. The actual upload will be be done by the class SharpeUploader.

class SharpUploader

To upload the flash image to the board you use the static SharpUploader class. You can start the bootloader by calling StartHalfKay(uint Serialnumber) (alternatively you can press the button on the board). After that you pass the flash image to the Upload member of the SharpUploader class. In the example below we upload the image to the first board we find.

USB_Device Teensy = Watcher.ConnectedDevices.FirstOrDefault();
int result = SharpUploader.Upload(FlashImage, Board, Teensy.Serialnumber, reboot: true);

The reboot parameter determines if the board shall be rebooted after the upload - which is what you usually want. The Upload function returns the following codes:

  • 0 OK, upload finished without error
  • 1 : No board with requested serialnumber and active HalfKay bootloader found
  • 2 : Error during upload of the firmware-

The repo contains a console application (FirmwareDownloadConsole) which demomstrates the use of the TeensyWatcher class.


  • Compatibilty to T3.5 and T3.6 added ** ToBeDone:** WPF example showing the usage in a more realistic scenario

NuGet packages

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