So if you checked out the first post in this series, you'll be familiar with the amount of work it took just to make room for the iPad Mini to be installed in the dash opening of our GTI, but that was really only the start. Since the concept was to make the finished piece look and operate much like a factory-installed radio, there was a bit of work to do next to achieve the desired functionality. In the process of making room, we removed the circuit boards from the factory radio that contained all the contact patches for the OEM buttons as well as the LEDs and potentiometers that control volume and other operations on the OEM unit. Adding remote buttons to control certain functions was up next... The original buttons on the face of the radio performed a number of functions - among them were FM, AM, Media, Setup, Mute, CD Eject and Tone Control. Since the original in-dash CD changer was going to be buried behind the iPad Mini (there hasn't been one CD played in this car since its purchase), and most of the radio's functions can be controlled through the steering wheel buttons, we selected certain buttons that were going to be needed and ones that wouldn't.
Another important detail of the installation is that we wanted to hide the iPad Mini's home button and sleep button so that the opening in the dash trim only showed the screen itself. With all this taken into consideration, we decided on four necessary buttons: FM, AM, Media and Home. These four functions would give all the control needed for the new setup.
This made it necessary to connect to only three of the many contact patches on the original circuit boards, while the Home button would be connected to a remotely mounted Bluetooth remote that would handle this function. In addition, there are of course the rotary controls for volume, power and radio tuning.
Extending out the contact patches for these three functions is pretty straightforward. Since we were using microswitches to control these, it's simply a matter of carefully soldering small gauge wires onto the circuit board traces for these three functions. We used a sharp Olfa blade to scrape away the protective coating on the traces leading to them and soldered away. Since the contact patches are simple momentary buttons, it was just a matter of getting a wire connected to the center and outer ring of each.
This was repeated for the three functions so that we ended up with simple pairs of wires that, when touched together or "shorted" would operate the function as if the original button was being pressed.
Eventually, the ends of the wires would be soldered onto microswitches that are controlled by the new buttons we fabricated in the dash trim piece - more on this in the next post. Control-wise, the last step was to disassemble the Bluetooth remote, which we sourced here. Again, it was just a simple matter of getting to the traces for the individual function we wanted to control - Home - and soldering on some small-gauge wire to imitate the button press. This Bluetooth remote fortunately has automatic pairing and auto-power off, so it was ultimately hidden under the console trim for easy access if batteries need to be replaced. Microswitches were soldered onto all of the leads we had created, and we ended up with this:
In these photos, you can see the small white rectangles that are the OEM LEDs which illuminate the buttons in the factory radio. We'll go into a bit more detail in the next post, but most of these ended up being used. The ones that weren't were simply masked to keep them from illuminating our new trim piece unnecessarily, but so that they could be used again if the factory radio is ultimately reassembled down the road.
As always, we appreciate our readers' interest in the projects we challenge ourselves with at 2point5, and we look forward to the next post detailing the creation of the trim piece that would house the iPad Mini, control buttons, rotary knobs and make the whole install look like a factory piece. Look out for it soon, and thanks for checking us out for step 2 of this project!