Getting Started Trouble Shooting Guide

Here are solutions to some common problems when getting started.

No devices appear in Device Explorer in Visual Studio (View/Other Windows/Device Explorer)

The Visual Studio nanoFramework Extension communicates to the device using serial/COM ports. The extension must first detect that the COM port is active, and then ping the port for a response to a specific query. The device drivers for serial ports come in many flavours and versions, and are probably the #1 problem with detecting and communicating with a device. Install the latest drivers for the USB chipset used by your board. Check the version using Windows Device Manager.
Sometimes unplugging and replugging the USB port will "wake up" a serial device driver
Try pressing the RESET button on your device to reboot it
Reflash your device to make sure it has nanoFramework installed
On the Device Explorer enable the Show Internal Errors button . Check for messages in the Visual Studio Output Window and select .Net nanoFramework Extension in the Show output from: dropdown.
Toggle the Disable Device Watchers button on the Device Explorer ON then back OFF. This will cause the extension to rescan all of the COM ports.
Try a different USB cable, or test cable on a known good device. Sometimes it is difficult to tell if a cable was only intended to be used for charging and does not carry the signal wires. Cables over 2M/6FT are to be suspected since those are often power only cables.
Some STM32 devices need to use two USB cables - one for power and one for serial/COM. See Getting Started Guide for managed code (C#).

An example of the error when the problem is version number. This was done by back-levelling the CoreLibrary to 1.10.4-preview.11 which was for the previous checksum. In this case the checksum was not checked - since the required native assembly version did not match the deploy failed prior to checking the checksum:

The C# and native C++ assemblies are not version aligned.
The C# version is determined by NuGet and the version of the component you selected. nanoFramework.CoreLibrary is the most common problem seen since it tends to load early.
The description of the NuGet package will contain the version and checksum of the native assembly that is required.
See Guide for package and assembly versions and checksums for more info.
Use the Device Capabilities button on the Device Explorer to see what assembly versions and checksums are installed on the device as part of the firmware.
If you are changing a nanoFramework component and you change the interface/contract of either the C# code or the C++ code, you will get a checksum mismatch error instead of a version mismatch error. This is the mechanism that prevents developers from breaking the contract without generating new versions and checksums.

Clear the cache at [username]\.nanoFramework\[device-name] - or just delete all of the cache folders.
Use the Device Capabilities button in the Device Explorer to verify the firmware version that is installed on the device.

Update your copy of the nanoff tool using the command
```
dotnet tool update nanoff --global
```
Run nanoff again, this time with detailed output messages by adding -v diag at the end. This will output verbose messages on the progress of the tool execution, hopefully detailing what could be wrong.
Make sure you have the latest drivers of the serial devices connected. Check the driver manufacturer website as not all of them make available the latest versions through Windows Update.
Check permissions for the cache folders at [username]\.nanoFramework. Deleting the cache files can sometimes fix problems.
Like the Device Explorer the flash utility depends on serial/COM drivers for most devices. Check that USB cables are not power-only cables (i.e. no signal wires), and that you are using the most recent USB drivers.

This is due to the nanoff will try to read and backup config partition before the actual flash.
If the chip is flashed with something else before (e.g. Arduino), it will cause a read error and stop the process.
Add --masserase to bypass the backup process and erase the flash.