Reverse Engineering Enables Slick Bluetooth Solution for Old Car Stereo

Those of us who prefer to drive older cars often have to make sacrifices in the entertainment system department to realize the benefits of not having a car payment. The latest cars have all the bells and whistles, while the cars of us tightwads predate the iPod revolution and many lack even an auxiliary input jack. Tightwads who are also hackers often remedy this with conversion projects, like this very slick Bluetooth conversion on a Jeep radio.

There are plenty of ways to go about piping your favorite tunes from a phone to an old car stereo, but few are as nicely integrated as [Parker Dillmann]’s project. An aftermarket radio of newer vintage than the OEM stereo in his 1999 Jeep would be one way to go, but there’s no sport in that, and besides, fancy stereos are easy pickings from soft-top vehicles. [Parker] was so determined to hack the original stereo that he bought a duplicate unit off eBay so he could reverse engineer it on the bench. What’s really impressive is the way [Parker] integrates the Bluetooth without any change to OEM functionality, which required a custom PCB to host an audio level shifter and input switch. He documents his efforts very thoroughly in the video after the break, but fair warning of a Rickroll near the end.

So many of these hacks highjack the tape deck or CD input, but thanks to his sleuthing and building skills, [Parker] has added functionality without sacrificing anything.

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Cyclist Pulled Over for Headphones Builds Neighborhood Shaking Bicycle Boombox

Riding around with headphones on is not the safest of things; those people are trying to could hit you! [Victor Frost] was actually pulled over for doing it. Although the bicycle police didn’t ticket him, they did push him over the edge to pursuing a compromise that lets him listen to tunes and perhaps still hear the traffic around him.

The build puts 200 Watts of audio on his rear luggage rack. He used a couple of file totes as enclosures, bolting them in place and cutting one hole in each to receive the pair of speakers. The system is powered by two 6V sealed lead-acid batteries which are topped off by a trickle-charger when the bike is parked.

Looking through this log we almost clicked right past this one. It wasn’t immediately apparent that this is actually version four of the build, and these are completely different spins each time. The top-down view of plastic-tacklebox-wrapped-v3 is sure to make you grin. Video overviews of the first two versions are linked in [Victor’s] details section of the project page linked at the top of this post. The progress is admirable and fun time digging through. They’re all quite a bit different but bigger, better, and more self-contained with each iteration.

Okay, okay, maybe this isn’t going to shake the neighborhood… until he adds a Bass Cannon to it.

Android Tablet Finds New Home In Car Dash

[Matt]’s 2008 Subaru’s stereo wasn’t really cutting the mustard for him anymore. He wanted to do something, something a little more custom than just an aftermarket stereo. After giving it some thought he decided he would try to mount an Android tablet in his car’s dash to act as a media player.

The HTC Evo View tablet appeared to be a great size to fit in the space left over from the stock radio, and it did fit nicely but there was a problem, the AC vent was in the way of the headphone and USB jacks! This was only a minor inconvenience for [Matt]. Instead of butchering the AC vents he decided to disassemble the tablet and see what the other options were. Luckily for him, both the USB and headphone jacks were on their own PCB boards. A quick slot cut in the rear tablet case allowed both connectors to now face towards the front of the car into the gaping crevasse the stock stereo once filled. Since the manipulated tablet case was facing inside the dash it wouldn’t create any unsightliness for the passengers.

With those connections out of the way it was time to focus on mounting the tablet in the dash. The stock trim panel that housed the old radio and two AC vents was modified with a hand-made fiberglass bezel to fit the tablet screen and make it look like the car came that way. The bezel was sanded smooth and painted to match the rest of the interior.

Originally,  [Matt] had to turn the tablet both on and off when starting and stopping the car. He then stumbled upon a product called the IOIO. The IOIO allows an Android device to interact with the inputs and outputs; both digital and analog, I2C, SPI and UART. It even has a voltage regulator that can take the car’s 12v supply and knock it down to 5 for the tablet. [Matt] also connected the IOIO to the car’s ‘ignition on’ circuit to turn the unit on and off with the car.

[Matt] plans on doing more with the IOIO’s capabilities in the future, but until then, he still has a pretty nice looking and unique car stereo.

$15 Car Stereo Bluetooth Upgrade

We’ve seen all sorts of ways to implement Bluetooth connectivity on your car stereo, but [Tony’s] hack may be the cheapest and easiest way yet. The above-featured Bluetooth receiver is a measly $15 over at Amazon (actually $7.50 today—it’s Cyber Monday after all) and couldn’t be any more hacker-friendly. It features a headphone jack for plugging into your car’s AUX port and is powered via USB.

[Tony] didn’t want the receiver clunking around in the console, though, so he cracked it open and went about integrating it directly by soldering the appropriate USB pins to 5V and GND on the stereo. There was just one catch: the stereo had no AUX input. [Tony] needed to rig his own, so he hijacked the CD player’s left and right audio channels (read about it in his other post), which he then soldered to the audio output of the Bluetooth device. After shoving all the bits back into the dashboard, [Tony] just needed to fool his stereo into thinking a CD was playing, so he burned a disc with 10 hours of silence to spin while the tunes play wirelessly. Nice!

Arduino Translates Signals Between Steering Wheel Buttons and Aftermarket Head Unit

There is no question that steering wheel mounted controls are super convenient. Reaching all the way over to the dashboard to change a radio station is so 1990’s. An ever-increasing percentage of new cars are coming equipped with steering wheel controls for the stereo, however, you’ll lose the button control if you change out the stock head unit to something a little higher in quality. Sure, there may be an adapter readily available for your car/stereo combination, but there also may not be. [Ronnied] took the DIY road and made his own adapter.

The first obstacle for [Ronnied] was to figure out the wiring on the steering wheel controls. After some poking around he found that there were only two wires used for all of the control buttons, each button only changing the resistance between the two wires. The button states could easily be read by using an Arduino’s analog input. A Pro Mini model was chosen for its small size as it could be housed in the radio compartment of the dash.

The next step was getting the Arduino to control the aftermarket head unit. [Ronnied] did some research regarding JVC’s Stalk digital control interface but came to the conclusion that it would be easier to direct wiring the Arduino outputs to the appropriate spot on the head unit’s circuit board. To do this the button for each function that would also be represented on the steering wheel was traced out to find a common point on the circuit board. Jumper wires soldered to the circuit board simply allow the Arduino to emulate button pushes. To ensure that the head unit buttons still work in conjunction with the steering wheel buttons, the Arduino would have to keep the pins as inputs until a steering wheel button was pushed, the pin changed to an output, the signal sent and the pin changed back to an input. This feature was easily created in the Arduino sketch.

Video below.

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Un-crapifying a Car Stereo

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[Noah Farrington] has just accomplished a major milestone in his life, purchasing his first car! A glorious 2001 Ford Focus wagon. While it may be a fully loaded luxury vehicle, it is missing one thing poor [Noah] can’t live without. An aux-in port.

He had a few options for rectifying the situation. Live with it as is, hack the strange Ford media protocol out of the back, or fool the CD player into playing his input. Naturally he chose the third option.

His first challenge was removing the deck from the car. People told him he’d have to buy fancy stereo removal tools — he made do with tent pegs and coat hangers. Using the same method as described in a past aux-in hack, he identified the audio in leads on the CD player’s ribbon cable. By carefully soldering in his own aux-in plug, he’s almost ready for business! Unfortunately, the CD player also needs to think that it is on for it to properly output the audio. [Noah] chose the simple solution — record a silent CD to always leave in the deck.

Stick around after the break to see it in action.

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Car stereo AUX input taps into CD ribbon cable

[Gezepi] wanted to add an auxiliary input to the stereo in his 1994 Camry. At first look there wasn’t an easy way to patch into the system. But a bit of probing with an oscilloscope and figured out that he could inject audio through the CD ribbon cable shown above. The CD reader is a self-contained unit that receives commands through the cable, and passes analog stereo audio back to the receiver portion of the head unit. We’re not sure how he figured out which pins to tap into, but it may have been as easy as probing with some headphones while a CD is playing.

The extent of his hack is documented in the image below. He cut the two audio leads on the CD side of the ribbon cable, then soldered his auxiliary jack on the receiver side of the cable connector. This ensures that two audio signals aren’t being piped into the receiver at the same time. Unfortunately it also means that he won’t be able to use the CD player. We have seen other methods that use a special audio jack as a pass-through which cuts the connection when a jack is inserted. That’s the method used in this Subaru hack.

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