Hands Free Cell Phone Hookup

[rvissers]

I know I saw it posted here some time ago but can't seem to find the link. There was a company that made an adapter that allowed you to hook your car handfree cell phone kit to the car using the cars antenna & the car speakers. It only worked for Onstar equiped SAAB's at the time, but they where working on a GM version. Anybody have the link?

 

[JS73751]

Any updates on this topic?

Thanks,
JS

 

[wyrickre]

I asked this question of UHLTronics on June 26, 2003:

I'm greatly interested in the Triad2 that you are testing on an Avalanche. Is the Avalanche being tested a 2002 or a 2003? There is a lot of differences between the 2002 and 2003 Avalanches as far as electronics... If you need a 2003 tester, I'd probably be interested!

I got this response on June 27, 2003:

Rob, you are correct about the differences between the two model year vehicles. Presently we are testing the Triad2 on the older vehicles, such as the 2002 Avalanche. Watch our web site for developments or e-mail us in about 3 months.
Thank you for your interest in the Triad2.
Respectfully,
UHLTronics LLC

 

[JS73751]

Thanks for the Update.
JS

 

[rvissers]

Rewbob, I am getting a similar response from them. Boy I am really growing impatient too.

Today I had a 'geek' lunch with some of the engineers I work with and we started talking about this mod. One of them finally said 'hey why don't you just forget them and build it yourself'. Then everyone started pulling out napkins and pens drawing all over the place (between the group we've got 'some' experience in this). Long story short if UHL doesn't get their act together soon me and a few of my friends might just do something.

 

[mtman]

Please! Assemble your group and build something for us all. I dropped an email to UHLTronics and there response was that the Triad2 for the 2002 Avalanche was still not completed and it would some time before the development was even started on the Triad2 for the 2003 Avalanche.

 

[mva]

Check out cellport.com. They may have what you're looking for.

 

[mtman]

I checked out cellport.com and was wondering if you or anyone else have tried to install the docking station? If so, was it difficult and how has it been working? Any feedback would be greatly appreciated. Thanks.

 

[jstafrk]

i have not done it, but what would be hard about it. most cell phone handsfree kits have a wire to mute the radio. this is what you will need to tap into as well as the speaker and mic connections. all you need is a diagram of the onstar wiring and it should be cake. if someone can get me a diagram, i could figure everything out.

 

[ShapeShifter]

i have not done it, but what would be hard about it. most cell phone handsfree kits have a wire to mute the radio. this is what you will need to tap into as well as the speaker and mic connections. all you need is a diagram of the onstar wiring and it should be cake. if someone can get me a diagram, i could figure everything out.

I agree that it would be simple, if only the radio had a mute line.

OnStar talks to the factory head unit via a serial data bus, and it splices the audio into the same inputs that a remote CD player or tape deck would use. My understanding of what happens when OnStar wants to use the speaker is that it sends a serial message to the radio (and remote tape/CD device if present) to say it wants to talk. The radio then switches to the aux input lines, the remote tape or CD mutes, and then OnStar can be heard on the speakers.

To do it right, you would need some sort of adapter kit that can understand and transmit these serial data commands.

The simplest way to do this on an '02 with an aftermarket installed handsfree kit, is to have the mute output from the cellphone trigger a relay. This is set up so that when the relay is activated, the relay contacts cut the power to the radio, efectively muting it. Now, other contacts on the relay can switch the speakers from the head unit to the phone. As for the microphone, they are so easy to install and unobtrusive, you're probably better off just installing the second microphone, rather than trying to tap into the existing.

I am considering using this brute-force relay method to mute my radio when a call comes in on my handsfree unit. I haven't decided if I will switch the speaker outputs or not. The remote speaker for the phone works just fine (hidden behind the center console by the heater vents), I only have a hard time hearing it ring while the radio is cranked up.

If you have an '03 all bets are off. My understanding is that there is no switched power lead into the radio. The radio turns on and off with the ignition based on serial data bus messages sent to it from the body control module computer.

-- SS

 

[ShapeShifter]

The simplest way to do this on an '02 with an aftermarket installed handsfree kit, is to have the mute output from the cellphone trigger a relay. This is set up so that when the relay is activated, the relay contacts cut the power to the radio, efectively muting it. Now, other contacts on the relay can switch the speakers from the head unit to the phone. As for the microphone, they are so easy to install and unobtrusive, you're probably better off just installing the second microphone, rather than trying to tap into the existing.

I am considering using this brute-force relay method to mute my radio when a call comes in on my handsfree unit. I haven't decided if I will switch the speaker outputs or not. The remote speaker for the phone works just fine (hidden behind the center console by the heater vents), I only have a hard time hearing it ring while the radio is cranked up.

Well, I went ahead and did this yesterday. I used a small RadioShack 12 volt relay (part number 275-249) with double pole double throw contacts, and put it under my center console under the cupholders.

Stock wiring is shown in blue.
​

The orange entertainment mute on my handsfree unit is normally an open circuit, and is grounded when the phone is active. So I wired up the relay coil between ignition swtiched (and fused) 12 volt power and the mute wire. Whenever the phone is is use, the relay is energized.

Then, it was a simple matter of routing the ignition switched 12 volt power through the normally closed contacts of the relay. The MP3 player was easy: the power line runs through my console, so it was easy to tap into that line. The stock radio was harder. I added a long pair of wires to the relay contacts, and crimped a male and female 1/4 inch spade quick disconnect on the ends. Then, I pulled out the radio, and on the black power connector is a dark green wire, top row second from the end next to an orange wire. This is the switched power line on a 2002 stock radio. I cut that wire, and crimped on another pair of male and female quick disconnects. Then, after routing the wires up behind the dash, I could simply connect the wires from the relay to the wires from the radio. When I go to sell the truck, and pull all this stuff out, I can simply disconnect the relay wiring, and plug the two remaining disconnects together to return to the stock configuration.

After putting it all back together, I tested it out, and it works great! As soon as I press a button on the phone, or an incoming call starts ringing, the radio and MP3 player shuts off. When the call is over, they both come back on and continue playing where they left off.

Now it doesn't matter how loud I crank the tunes, I can always hear the phone when it rings.

-- SS

 

[CraigF]

Great job SS.

What kind of phone/hands free kit do you have?

Craig

 

[ShapeShifter]

What kind of phone/hands free kit do you have?

A Motorola T720 flip phone with a Motorola hands free kit. More details are on my personal web site. Click on my signature pic, then Modifications, scroll down and click on CellPhone/GPS.

This is what it looks like:

​

-- SS

 

[danlwil]

SS,

that has to be one of the sweetest setups I've seen....

Looks like my wish list just got longer

 

[ShapeShifter]

that has to be one of the sweetest setups I've seen....

Thanks, it does make a nice little "command central."

Looks like my wish list just got longer

I'm happy I could help.

-- SS

 

[rvissers]

Love that mod ShapeShifter....maybe I won't wait for UHLTronics afterall...

This is the latest post on UHLTronics;
Saturday, July 19, 2003
[cut]
To keep you updated, the Triad2 had to go back into re-design and will be available for beta testing soon. We look forward to working with you.
posted 7:54 AM

 

[ShapeShifter]

Love that mod ShapeShifter....maybe I won't wait for UHLTronics afterall...

To be fair, the UHL system is a lot slicker: it ties the sound output from the cell phone into the radio. This means that the sound comes out of the radio speakers, and probably also means that the radio volume control is also used to set the volume. Very slick and convenient. Also, since it simply mutes the sound, whatever you were playing before the call should come back on quickly. On the downside, the UHL system is expensive, limited to Nokia phones, and not yet available.

With my method of killing the power, you must either use an external speaker with the handsfree kit (which is what I did) or use extra relay contacts to switch the speakers from the radio to the cell phone (which would require cutting/splicing more stock wires.) Also, since I am not muting the radio, but rather turning it off, there is the normal power on lag to restart the music, the sound does not come back on instantly. On the other hand, this is an advantage in that the CD you might have been listening to had stopped, and did not continue playing while you were on the phone.

Pros/Cons:

• UHL:
  • Pro: Clean installation
    Pro: Plays through radio speakers
    Pro: Fast end of call response
    Con: Cost
    Con: Limited to Nokia phones
    Con: CD keeps playing
  Relay:
  • Pro: Cost
    Pro: Readily avaialble
    Pro: CD stops while on phone
    Pro: Works with any phone with a mute signal
    Con: Installation effort
    Con: Must cut/splice stock radio power wire
    Con: External phone speaker
    Con: Takes a few seconds for music to start after call

Plusses and minuses either way you look at it. In the end, I went for price, availability, and Motorola compatability when I chose the relay method. (Plus it gave me an excuse to design and work on a mod. )

-- SS

 

[rvissers]

I'd only add one thing, they are planning on supporting Motorola phones. When I signed up for beta testing they were very interested in my StarTac & Future T720 (which I have now) in part because they said they plan on supporting most Motorola phones (what that means is another question).

 

[jpicconi]

I had the same problem when I was putting in a bluetooth car kit in my AV. Since there is no mute input in the head unit, I used an accessory connector that they sell called the HCE-16 advanced music mute. It splices into the speaker wires and contains a mute switch. I used an additional wiring harness for the stereo, so that I can always pull it out later. The only problem is that your stereo has to be on, as the cell phone signal is run through the stereo amp, but otherwise, it works like a charm.