Connect Development Board To Computer

You got a new development board, and now you want to hook it up to your computer (so you can program it and upload new firmware, or receive output via the Terminal window).

Sounds easy: just connect a USB cable to the development board and plug its other end into your computer. And often enough it is that easy. If it works like this for you, then you can skip the remainder of this article and move on to the next.

If however your computer simply won’t recognize the board, or if you’d like to better understand what goes on exactly when you connect your development board to a computer, please read on. Most likely, you’ll be able to fix your connection issues in no time and learn a lot of new things.

When things don’t work as expected, some users are quick to blame the board or brag about the “rotten quality” of Asian sellers. That’s not so clever. Initial connection issues are actually very common and most likely caused by easily fixable user errors. True hardware defects are extremely rare.

USB-to-UART Chip

Most microcontrollers do not support USB directly. They need a chip that translates between the USB port of your computer and the serial interface of the microcontroller.

External Programmers

These chips are available separately in many different form factors and can be used to connect directly to microcontrollers, i.e. to occasionally update the firmware on devices.

They come with a USB Connector that is wired to a USB-to-UART (aka USB-to-Serial or USB-to-TTL) chip:

On the opposite site, there are connectors for wires that can be connected to the RX and TX pins of the microcontroller.

If you use external programmers, always make sure to connect RX to TX, and vice versa. Typically though, you will be using a built-in programmer (see below).

Built-In Programmers

Development boards are targeted towards users that need to frequently update the firmware because they are testing and playing with microcontrollers. Wiring up an external programmer would be inconvenient.

That’s why most development boards come with USB-to-UART chips that have USB connectors built-in:

Connecting To Computer

When you connect a development board (or an external programmer) to the USB port of your computer, the USB-to-Serial chip should be immediately recognized as a newly discovered Plug&PLay USB device. The typical sound for a newly discovered USB device should play on your computer when you plug it in.

1. Plug in a USB cable into the development board.
2. Once you plug in the other end of the USB cable into any USB port on your computer, the computer immediately plays the sound New USB Device Discovered.
3. In Device Manager (on Windows), a new COM Port appears.

The USB-to-Serial chip provides a new serial port that can be used by your computer software like any other built-in serial port.

If your computer does not recognize the USB-to-Serial chip when you connect a development board to its USB port, and you don’t see a new COM Port in device manager, don’t panic: your computer may just be missing a driver. See next section for fixing this issue.

# install module from Microsoft PowerShell Gallery (https://www.powershellgallery.com/packages/DoneLandTools/)
Install-Module -Name DoneLandTools -Scope CurrentUser -Force

# run com port diagnosis command
Get-ComPortInfo

PS> Get-ComPortInfo


Name          : USB-SERIAL CH340
ComPort       : COM4
Manufacturer  : wch.cn
DriverPath    : C:\WINDOWS\SYSTEM32\DRIVERS\CH341S64.SYS
DriverVersion : 3.50.2014.8
DriverName    : CH341SER_A64

Name          : USB Serial Device
ComPort       : COM77
Manufacturer  : Microsoft
DriverPath    : C:\WINDOWS\SYSTEM32\DRIVERS\USBSER.SYS
DriverVersion : 10.0.19041.3636
DriverName    : usbser (Microsoft USB Serial Driver)

Drivers Required?

What if the computer simply ignores a connected development board (or external programmer) and does not assign a COM Port to it? This is solely an issue between your computer and the USB-to-Serial chip. There is nothing else involved, especially no configurations or settings in your IDE.

Ruling Out Physical Problems

Before looking at driver issues, make sure there are no physical problems. *Physical problems are by far the most common causes and simple to fix:

• Loose Connections: make sure you firmly plugged in the USB cable. It should snap into place.
• Bad USB Cable: this is meant dead serious. Some USB cables are made just to supply power and do not connect the data lines, but the majority of cables connects all pins. Still, a great many USB cables cause connection issues, most likely due to low quality, high cable resistance, loose jacks, etc. The best option is to use a known good USB cable that you previously successfully used to connect to a breakout board. If you don’t have such a cable, make sure you try and test as many different cables as you can get a hold of, and if the cable was indeed the issue, attach a label to the cable that finally worked so you know which one to use in the future.

Installing Drivers

If you came this far and still have connection issues, now is the time to check for missing drivers.

In order to use the USB-to-Serial controller on a board, the computer needs a driver for it. If a board is not recognized by your computer, and you checked all other causes mentioned above, then most likely it is missing the appropriate driver.

Most development boards and external programmers use one of these USB-to-Serial chips that all work similar:

Their primary difference is the transfer speed that determines how long in takes to upload new firmware to the microcontroller.

Here are the steps to fix missing drivers:

1. First try and identify the USB-to-Serial chip you are trying to connect to. On most development boards, it is the second-largest chip on the PCB. Occasionally, though, this chip can be unmarked, or its markings are unreadable.
2. If you do know the type of chip, click on the appropriate header in the table above, or use the table below, to visit the chips’ manufacturer driver downloads section. Download the driver for your computer operating system. If you don’t know the chip type, you go by trial and error and install one driver at a time. You may end up installing all three drivers (which isn’t a bad thing).
3. On Windows, right-click the downloaded driver archive, choose Properties, then Unblock the file.
4. Extract the archive and run the installer.
5. Once the driver has been installed, try again connecting the development board. Most likely, its USB-to-Serial chip will now be recognized, and you get a new serial port.

Hardware Issues

Rarely, the USB-to-Serial-Chip and the USB connection are fine, and still the development board won’t respond correctly.

If you have installed all drivers, restarted the computer, tried different USB cables and made sure all connections were plugged in tightly, then (and only then) it is time to consider a board defect.

Verify Board Defect

To verify, try connecting a different development board (ideally of the same type requiring the same drivers). If the new board connects fine, you ruled out the most common causes for connection issues (USB cable problem, missing driver), and it most definitely is a board issue.

Even the cheapest development boards typically work great provided these boards were assembled right. One reason for cheap prices is poor quality control: faulty assembly goes unnoticed, and roughly out of a hundred boards may have a hardware issue. Then again, you often get ten no-name boards for the price of one from a renown brand. Even if one out of these has a defect, it’s still a good choice for hobbyists that are willing to test boards themselves.

Here are the typical two hardware defects:

• Bad USB Connectors: occasionally, the USB connector is not firmly soldered onto the PCB, or the connector itself is slightly off specifications, causing loose contacts.
• Bad Soldering: drops of solder may have caused a short circuit on some pins. When the board gets warm quickly after supplying it with power, immediately disconnect it and closely examine all solder spots.

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