Hardware Volume Control Knob Configuration and Windows Upgrade

Hello and welcome to post #14 of my blog on building a comprehensive in-car entertainment and navigation system

In this post I'll cover a few major changes that were made to the computer's software, and an important and vital hardware addition.

To start off with, I'll outline the situation with windows. It was deemed necessary to upgrade from windows 8.1 to windows 8.1 pro, because of the extra features and native remote desktop functionality it provides. Achieving this was a huge effort, however, as using the "upgrade" option on the virtual installation disc downloaded from Microsoft didn't work.

Because of this, I had to do a clean install on the computer which resulted in many many hours of effort in re-downloading the drivers (I didn't keep the old ones as I thought I had no need for them) and re-installing them and the applications originally on the car computer, as well as all of the updates for windows. On top of this, I had to manually upgrade to windows 8.1 pro from windows 8 pro as for some reason it would not install the update automatically. 

Once windows was reconfigured and all the drivers and hardware working properly, it was time to address a major usability issue that was outstanding on the computer since its first use.

This is that trying to adjust the volume while driving is extremely difficult. On windows 8.1, the easiest way to change the volume was to bring up the charms menu by swiping from the right side of the screen then tapping settings, then tapping and dragging the volume icon to the desired level. Not ideal at all. A tactile system was needed - ie a volume control knob akin to what almost all conventional car head units have.

To achieve this, I decided on a fully digital solution, rather than simply wiring an in-line volume control knob in series with the recently reworked RCA connection system (see previous post). The advantage of this is the volume can still be remotely adjusted from phones and there is the added redundancy of still being able to adjust the volume using the method outlined above.


After some searching I found this little gem, a rotary encoder based volume control knob that was designed specifically for in-car PC applications. One order from amazon.com and two weeks later and it was delivered to my door.

The unit itself is relatively simple. It connects to the computer via the supplied USB cable and will work with windows out of the box to control the volume without any need for driver installation. While not cheap, the unit seems to be of good quality and is properly and thoughtfully designed.

Turning the glowing knob adjusts the volume, and pushing it mutes all audio. In addition to this, it is backlit with a RGB LED and is able to be set to any color via software downloadable from the manufacturer's website. The blue power LED (see above photo) is also fully dimmable.

However, windows does not support the drivers for the LED control functionality, and manual driver installation was required. The supplied instructions asked me to manually install the drivers using device manager in Windows, however on windows 8.1 pro this proved difficult. 

Windows 8.1 would not let me install drivers that are not digitally signed (the unit comes from a small developer who for one reason or another has not signed his work), so It was necessary to activate the advanced start-up mode in Windows and disable the driver signature enforcement setting. I used this tutorial to achieve this.

However, this caused further complications, as an unknown error was preventing windows from rebooting into advanced start-up mode

This error would appear during restarting right before the PC power-cycled itself, giving me about 1.5 seconds to read it before the screen went black. The PC would then boot up normally into windows after instead of launching advanced start-up. This is an extremely frustrating and potentially dangerous condition as if there was an fault preventing windows from booting advanced start-up would not automatically launch, leaving me little options for recovering the PC.

After consulting my IT professional friend and some forums, I tracked down the cause of the problem. The CSR wireless Bluetooth stack software supplied with my bluetooth dongle was causing a windows C++ runtime error. To fix the problem, I had to uninstall the wireless stack and drivers, launch advanced start-up, disable driver signature enforcement, install the LED control software driver then reinstall the Bluetooth stack and reconfigure the dongle. A lot of work for such an arbitrary error!

Once the drivers were installed, the volume control knob was fully functional.

LED control software

The simple but effective software allows the user to pick any colour or brightness for the volume knob to glow, and control the brightness of the power LED. This only needs to be done once, as the program saves the settings in the unit's on-board micro-controller. Also Included in the software pack is the ability to flash new firmware to the volume control knob.

The unit still needs installing into the car's dashboard next to the screen, and a USB extension cable ran from the computer to the unit. I will do this when I have more time

I'd like to thank my friend once more, without your help I would still be stuck trying to install the driver software for the LED's!

That's it for this post, keep reading for future updates. As always, thanks for reading.