DIY: A better Bluetooth phone/A2DP upgrade (w/ auto-switch to AUX)

[awoolf]

This turned out to be quite a fun project! This is my first 8thcivic.com DIY, so message me if any descriptions or pictures could be clearer.

SCOPE OF PROJECT:
Integrate an inexpensive Bluetooth phone/music system with the factory audio system in my 2008 Civic Si.

I first tried the Grom Audio USB/iPod/AUX interface car kit, and added the optional Bluetooth module. (~$180 total) It a was thoroughly disappointing experience. I searched for other options, offering either better functionality or a lower price. I settled on hacking the very reasonably-priced (~$35 on eBay) Jensen BT360 Universal Bluetooth add-on kit. (It appears to be sold overseas under other brands [Triamp/Viseeo] & models [CK-360/CK-361/VK-Q2].)



The BT360 is a mid-range model from Jensen. Cheaper models don't have LCD displays or A2DP support, and more expensive models use big ugly LCD displays & include a wireless remote mounted to your steering wheel. My preferences leaned towards an unobtrusive display with a wired remote control, but this modification will work with any similar Bluetooth setup.

As shipped, the BT360 is a mish-mash of audio outputs and features. Bluetooth phone audio is played through an external speaker that mounts under the dash, and A2DP music playback is broadcast by an internal FM transmitter. A "mute" output wire activates during incoming or outgoing phone calls, so if your car stereo has a mute input, the sound will be muted until your call ends.

It's intended installation is pretty easy (only 3-4 wires), but not quite what I'm looking for. I'm a hacker, so let's hack it up!

PROJECT GOALS:
1. Get rid of the included external speaker and have the phone audio routed to the existing front speaker(s).
2. Bypass the FM transmitter and wire the A2DP (music) output directly to the AUX input of my Honda navigation system.
3. When a phone call comes in, have the factory radio automatically switch to the correct audio input.


1. HACKING THE BT360:
I originally intended to use a DPDT relay to connect the Bluetooth box to my left front speaker, switching the speaker to the Bluetooth box whenever a call was active. But while testing the BT360, I found that the phone audio was also output over the FM modulator, not just to the external speaker output. Based on the rest of my project, this modification to the speaker wiring was no longer needed.

Next, I needed to determine if I could bypass the FM transmitter and grab the R/L audio signals directly. Inside the BT360 box, the FM transmitter module was easily located. Luckily, the R/L/Gnd pins were clearly marked, and a quick bit of soldering ran both signals out to a mini-headphone cable.





2. DESIGNING THE ADAPTER BOX:
It would've been easy enough to just plug the Bluetooth audio into the existing AUX jack. But, that would be ugly, and I wanted the radio to automatically switch to the Bluetooth phone audio when a call comes in.

As mentioned in several other DIY articles here, the original AUX jack has five/six pins. Three are for audio (R/L/Gnd) and two connect to a switch. When a cable is plugged in, the switch is activated, and the radio selects the AUX input. So, all we have to do is wire the Bluetooth box "Mute" output to short these pins, right? Not quite that simple, if we want to keep the AUX jack usable.

If something is plugged into the AUX jack but you are listening to a different source (FM/CD/etc), shorting those pins won't switch the radio to AUX, because they are already shorted together. I could've lived with the limitation, disabled/removed the AUX jack, or hacked together a working solution. Guess which one I picked?

The radio switches to AUX when it senses a cabled plugged in. So, to automatically switch to the AUX input, we must simulate unplugging and replugging the AUX jack. I found that a ~1/4 second delay was needed for the radio to sense the change. (With anything shorter, the radio didn't notice the change.) After investigating at a few possibilities for inserting a short delay (555 timer, etc), I came up with an easy solution using only a few simple components.

A small capacitor is used to supply a short burst of power to a relay. The relay is wired to have the AUX jack's switch wires connected together by default ("NC" - normally closed), and it then disconnects them for a short time when "Mute" becomes active. I tried several capacitor values, and found that 330 uF would power my relay for ~1/4sec. The capacitor is charged through a resistor, which has to be small enough to quickly charge the capacitor, but large enough to keep the relay from staying "on" after the capacitor is discharged. In my case, ~5k ohm worked out about right.

Because I wanted to keep the AUX jack functional, I need to be able to disconnect any incoming audio when a phone call is active. A "dual pole" relay passes the AUX jack R/L signals along to the radio. When the "Mute" line is active, the relay is activated and interrupts the incoming AUX audio.



How to determine capacitor/resistor values for your relay:
1. Test several capacitors by charging them with 12V and then connecting across the coil on your relay. Find the value that activates the relay for about 1/4 second. (probably 200uF-1500uF)
2. Power your 12V relay through a 1/2W (or larger) potentiometer set to 0ohm, and increase the value until the relay turns off. (I used a 50K pot, and found that my relay turned off at about 4K. I rounded up to 5k to be sure it would turn off reliably.)


3. BUILDING THE ADAPTER BOX
I bought the smallest, lowest-power 12V DPDT relays at my local electronics shop. They are only rated for switching 1A, but that's plenty for our purposes. (You could also use 2 DPST relays, or a DPST and a SPST relay, all with "NC" contacts.)
A few CD-audio cables were recycled to connect the AUX jack and radio's AUX input. (CD-audio cables are only 4-pins, so the pins were moved over to a 5-pin connector)
A 5-pin male-male connector adapts the modified CD audio cable to connect to the female AUX cable from the radio.
A stereo mini headphone jack is the input for the Bluetooth box's audio output.
Everything was assembled on a small Radio Shack circuit board and mounted in a small (1"x2"x3") project box.

Total cost was about $20, buying all the parts locally at retail prices. Purchase from Digikey or Mouser, and you'll probably be closer to $10.




4. PUTTING IT ALL TOGETHER



I used information from the various DIY threads here to remove the dash panels and center console.
Power was tapped from the main radio connector, using 3M T-Taps for easy removal down the road. (Pin 10 is constant 12V, Pin 13 is switched 12V)
My adapter box gets its power from the bluetooth box harness.
The Bluetooth box and adapter box were mounted in the center console, in the empty space under the front pocket.
Ground was connected to a mounting screw in the center console.



I decided to mount the controls to the left of the steering column, after moving the VSA button. The controls are easily visible from the drivers seat, and are close to the existing steering wheel audio controls. Microphone was installed on the other side of the steering wheel, behind the empty 3-slot opening near the ignition switch.




5. DONE! - DOES IT WORK?

Bottom line? It works pretty darn well for ~$50.

The display/control box doesn't "fit in" with the stock interior as well as I would like, but it's not too bad.
(It looks worse in the pictures - it blends with the dark panels in real life.)

Benefits:
About $50 installed - can't beat that!
If I'm listening to FM/AM/CD when a call comes in, the radio switches over to AUX automatically.
If I have an iPod plugged in to AUX when a call comes in, it mutes the iPod audio automatically.
I've been told that the call quality is quite good. (People can hear me just fine)
Play/Pause/FFWD/RWD controls all work well with my Android music playback software.
Long-pressing the "End Call" button lets me voice dial my Android phone. (Long-pressing "Answer Call" button redials last number)

Downsides:
A2DP audio doesn't have the same deep bass as a direct cable from phone to AUX jack. (The sound quality is about the same as the ~$180 Grom setup, so is probably a limitation of A2DP)
After a call disconnects, the radio stays on AUX. (Good if I was listening to Pandora/iPod/etc, bad if I was listening to FM. But, one button press on the steering wheel controls takes it back to FM)
Buttons on control panel aren't illuminated.

[awoolf]

...reserved...

[civictypracer310]

Nice write up

[kt1982]

thanks!

[ifourm]

This looks awesome!

[guzzler]

Awesome! this is what i was looking for! Just got my BT 390 (same as 360 except for the remote is wireless).

One question: I understood the part of soldering R/L and Ground from the small FM board, but how did you disable FM module?

[awoolf]

Originally Posted by guzzler

I understood the part of soldering R/L and Ground from the small FM board, but how did you disable FM module?

My first try involved removing the FM module, and grabbing the audio coming from the main board. But, the raw audio signals appear to be balanced - neither the + or - was equal to ground. and connecting either to ground rebooted the device.

So, I just left the FM tramsmitter module in place. I'm grabbing the audio as it goes into the FM chip, so it doesn't matter what frequency it transmits on. The antenna connects to the vehicle ground, so removing it should greatly reduce the range of the FM signal. (It's the black wire snaking across the board in the pic below)

[armokaiser]

very details...thanks

[xghostyxjokerx]

any vids?

[DrClaw]

What did you dislike about the GROM unit? I have it in my car and have no experienced any issues (other than in call echo due to using a mic w/o active canceling).

[awoolf]

Originally Posted by DrClaw

What did you dislike about the GROM unit? I have it in my car and have no experienced any issues (other than in call echo due to using a mic w/o active canceling).

It's been quite a while since I used it, but if I remember correctly:

They shipped the item with the wrong firmware.
The included manual didn't match the functionality of the item.
Nowhere on the website was a real manual for the "XM-emulation" mode; I had to request it from their tech support.
The controls are VERY counter intuitive. Here are a few excerpts from my support email thread with Grom:

Thank you for your reply, but that guide doesn't help much. I was expecting a proper manual for the very different operation of the unit in XM-emulation mode.

The unit does play, and does display track information on the radio's XM display. According to the "hondaxm.pdf" guide you sent, I should be able to FFWD/RWD, change "disc"/folder/playlist, and skip to previous/next track. But, ALL my radio's controls seem to do the same thing - skip forward or back one track. (1/2, 3/4, 5/6, Steering wheel +/-, Steering wheel +/- "long-press", Tune +/-, Tune +/- "long-press" - all only skip one track forward and backward.) I can't FF/RWD and can't change playlist/"disc"/folder. Occasionally, a "long-press" of "Tune +" will skip forward TWO songs rather than just one.

My 2008 Civic Si w/ factory Navigation looks exactly like this 2007:
2007 Honda Civic Si navigation system

Looking at your "hondaxm.pdf", it shows controls for a non-navigation radio, and they are mapped as follows:
# (Honda)- GROM
-------------------------
1 (Disc +)- Fast Rewind
2 (Repeat)- RANDOM
3 (Random)- Fast Forward
4 (Disc -)-
5 ( )- Prev Disc
6 ( )- Next Disc
>> (Seek+)- Next Track
<< (Seek-)- Prev Track

The navigation radio has controls laid out differently. Here's how I believe it SHOULD be mapped to the buttons:

# (Functn)- what GROM function should be
----------------------------------------
/\ (Tune+)- Next Track
\/ (Tune-)- Next Track
/\ (Tune+)- (LONG PRESS) Next Playlist/Disc
\/ (Tune-)- (LONG PRESS) Prev Playlist/Disc
1 (Repeat)- Repeat
2 (Random)- Random
3 (RWD )- Fast Rewind
4 (FFWD )- Fast Forward
5 (Skip)- Next Track (or maybe next folder under current playlist/disc, or skip 10 tracks?)

I'm having Bluetooth problems as well:
TERRIBLE A2DP sound quality. When my phone is connected to the existing AUX jack on my radio, it has excellent audio quality. When connected through your bluetooth device, the audio sounds tinny and has NO low-end (bass).

I have to un-pair and re-pair my Samsung Galaxy S phone every day (Sprint Epic 4G). My phone bluetooth sees the GROM-CAR device and shows "Paired, but not connected". When I try to connect, it fails. Tried several times, tried rebooting the phone, tried power cycling the car - nothing works. I have to delete the GROM device from my phone's bluetooth, power cycle the car, and then re-pair it. It will then work for the rest of the day, but won't work the next day.

My previous vehicle had a Pioneer AVIC-D90T navigation/dvd radio, and the same phone worked fine - no issues connecting automatically. (It didn't support A2DP, but did support bluetooth calls/etc)


Do you have a firmware that support the navigation radio in the 2006-2011 Civics? If not, are you working on one? Is there a configuration file that I can edit to assign particular functions to specific buttons?

I WANT to like your product, but so far I'm not impressed. You either need to resolve these issues, or open up the firmware so folks like me can tweak it to our liking.

(SEVERAL OTHER EMAILS BACK AND FORTH, THEY RESOLVED SOME ISSUES, SOME REMAINED. BELOW IS MY FINAL EMAIL, REQUESTING A RETURN/REFUND)

I was able to find the "Mode" on-screen button. Once the mode has been changed to "Category", the steering wheel controls DO work to change to another playlist. (Short press changes track up/down, long press changes playlist up/down.

I still have several problem though.

The unit was advertised with (and included manual shows) the following features, none of which are available on this unit with the firmware you advised:
FFWD / RWD while playing a track.
Skipping 10 tracks ahead in the playlist.

Obvious functionality missing from this device that any reasonable MP3 player would include:
Ability to change albums/folders directly (not just skipping tracks 1 or 10 at a time)

The functionality of this device is not as advertised and shown on your website, and it below the minimum standards expected of such a premium-priced product. As per the eBay auction description, this item can be returned with in 30 days. I would like to send it back for a full refund.

Where do I need to send my formal RMA request?

It didn't workr very well as an MP3 player, and the bluetooth was flaky. My cheap solution above allows me to easily use my phone for music playback, and the bluetooth "just works" with all the various phones I've used.

Does this answer your question?

[DrClaw]

It absolutely answers my question. Sorry to hear about your bad experience. I suppose I am lucky to not have those issues. I went with GROM mainly because I wanted something that would let me use the steering wheel controls to skip tracks and it does just that. I have Beats audio baked into the ROM on my phone so that it increases bluetooth audio quality.

[ApexPredWolf]

looks really good nice diy

[zeeden]

Nice write up. Could you make me one? I'll pay

Sent from my Galaxy Nexus using Tapatalk

[nachosanch]

thanks! nice DIY

[Vizy]

Originally Posted by zeeden

Nice write up. Could you make me one? I'll pay

Sent from my Galaxy Nexus using Tapatalk

same lol!! I'd be down to pay for something like this! op where r u located lol? Socal by chance?

[98koukile]

Since I went with the ms8 and not a new headunit I've been looking into this more and more... too bad all the complex wiring has me spooked because this would be an awesome solution.

[BlurpleFG1]

Originally Posted by 98koukile

Since I went with the ms8 and not a new headunit I've been looking into this more and more... too bad all the complex wiring has me spooked because this would be an awesome solution.

Check out the USA Spec BT35-HON. It's very easy to install.

Sent from my SGH-T999 using Tapatalk 2

[98koukile]

I could probably pay someone to install this one for cheaper overall than that one, thank you for the suggestion though.

[awoolf]

Originally Posted by Vizy

same lol!! I'd be down to pay for something like this! op where r u located lol? Socal by chance?

I wish I was in SoCal...
Kansas, actually.