Many people ask how to build one. Let me tell you it is not very easy.
The device consists of two parts a D2B audio controller and a Raspberry PI which handles the Bluetooth streaming. The latest version of the unit user Raspberry PI Zero – the regular, not WiFi version.
The two boards connect together via 40 pin header. The D2B unit receives audio via I2S protocol from the Rapsberry PI. The two units also communicate via serial interface. The Raspberry PI is powered by the D2B audio unit. The D2B audio unit also can reset the Raspberry PI board if it is not responding to serial commands.
Here is the schematics of the D2B unit. Jaguar D2B board There are two unmarked diodes D201 and D301, part number should be 1N4148WS in SOD-323F package. LEDs are generic type in 0805 package – any color of your choice would work.
The micro-controller is Cypress PSOC4 4100 series. Here is the firmware it is running. You need to use an SWD programmer to load the firmware onto the board. The cheapest one is probably the CY8CKIT-043 kit. The small board with the USB connector can be snapped and used as SWD programmer independently.
The Gerber files that one can use to make the PCB.
The demand for my CD-changer emulator is picking up, so I’m making several boards at the same time. Placing of the components on the board by hand and re-flow with hot air.
These 6 board take about 4 hours in this stage plus another 4 hours or so to solder the optical connector and other connectors. My hands feel tired after a while. I’ve heard that good scotch helps with this condition.
I had to re-design the new box. Before I was trying to make it from 2 parts – top and bottom. This process had issues because the bottom part would not 3D Print correctly – it would keep curling up due to stress in the ABS material.
So finally I made the box bottom from several pieces. The bottom has 4 curved corners and 4 side panels, which slide down – you can see one of the side “panels” in this picture.
Also, you can see the size of the old device version compared to the new version.
This was one of my favorite color combinations for the box of the CD-changer emulator device. This version has vents on the side – not because the device was overheating, but the box was easier to print this way. Without the vents, the ABS plastic would curl up, and the box looked very weird.
With this particular unit, I had some trouble with the optical connector not locking to the plug and had to improvise with some wire to hold it in place.
By the way, this re-design of the unit box was prompted by customers returning the device in half-melted form. In the initial version, the box was printed out of PLA which was getting soft in the summer temperatures in Texas and Arizona.
So I had to print all plastic parts our of different plastic – ABS, which has a higher melting temperature.
My gracious “beta” customers returned their units, and I provided them updated devices with the “final” form factor.
This allowed me the opportunity to take a picture of the “beta” version of the CD-changer emulator unit.
You can see that the fiber-optic connector is a separate board. Initially, I designed it like that because I was planning to have a version for Jaguar cars as well as Mercedes-Benz cars. The only difference between them being the optical connector. It did tun that the Benz people are far less enthusiastic about the product, so I simplified the “final” board with the connector onboard.
In this version, the Raspberry Pi was on the side of the control board, and there is a whole lot of wires going around.
The final version was much more compact and easy to make.
I was very happy reaching this point. I was quite a few years of effort, but finally, here it is. Something I can offer to people – a useful product. A device which emulates the car CD-changer and lets you stream music from your phone via Bluetooth.
Following a short beta test period, this is the re-designed look of the CD-Changer emulator. The fiber-optic control board is now on top of the Raspberry Pi. You can see the fiber-optic transmitter glowing in red through the connector plastic housing.
The board says V3.0 because V1 was the “beta” device and V2 never saw the light of day. The board has the D2B controller OCC8001 as well as a Cypress ARM M0 micro-controller and finally power supply circuit.