Hack a Gm Radio Under 40$

Intro: Hack a Gm Radio Under 40$

In this I'able I will detail how to install a Bluetooth headset directly into your radio head unit to remote control your head unit from your phone.  

STOP, PLAY, Volume up, and Down, direcly through BT, on your wireless device.

Now I have a old 2004 GM Colorado first Generation, my radio is a simple CD player/Radio.  In order to put Aux radio jack into this radio GM requires you purchase an 80$ encoder dongle.  This IS NOT Needed.

Matter of fact this was so simple I was shocked.   

Now this should be do able on any radio, but this method details on GM radios.

As for operation, simply turn the BT unit on, it will Directly override the radio signal.  for best results turn the radio volume down, and use the remote blue tooth connection to volume up and down.

I use this everyday with my droid 4 to play audio books from my audible account.

Enjoy, I hope this works if you have any questions leave a comment.

STEP 1: MAT'S and TOOLS Required.

This is a list of tools and materials you will need.

TOOLS

1. Soldering tools.
2. Pliers
3. small socket set.
4. Magnifying devices
5. 1/2 inch drill bit, to install switch.
6. Drill (not pictured.)

MATS

1. small Bluetooth headset A2dp compatible, or Stereo ready. 24$ Amazon HM3500
2. mad soldiering skills.
3. Roll of wire.  $5 Radio shack
4. Two Types of switch, 1 Momentary and one on/off toggle. - $7 radio shack
5. a scrap wireless car charger.
6. Solder.
7. Radio. - free use your old one
8. Electrical tape. - barrow some
9. 1x headphone jack stereo ready. - 2.29 Radio shack

Chip diagram for radio.

STEP 2: Removing Your Radio.

My radio is a 2004 GM RDS/RD air first Gen digital radio.   

It was held in by three bolts, after removing the faceplate; which was held in by three friction clips I simply slipped it free from the chassi and removed the two connector plugs,  Will be 2 one for radio power and speakers and a second for your antenna.

STEP 3: Breaking Down Your Radio.

on my radio there was two snap on plates that covered the bottom and the top, simply remove these.  after the top cover is removed there are like twelve small clips which held the face plate on.

STEP 4: Viewing Your Radios Brain.

Essentially you will be creating a direct speaker input for your Bluetooth headset. Using a small headphone jack.  Here is how it is done.

Now my radio uses a Saa7706h Digital signal processor, I google my chip and pulled the PDF data sheets.

There are 4 pinouts you are looking for  FLV, FRV, RLV, and RRV  These pins are chips output pins and led directly to the amplifier, but after the volume controller.

I wired my connections directly to  FLV, and FRV,  using a small 3 pin stereo head jack,  I used a Ground located on the side of the radios board mount.

To get some perspective on your chip the number one pin should always be located near the dimple on the chip.

STEP 5: Installing Your BT Headset.

1. First step is to take a small screw driver and pry the BT head unit apart.    inside there will be a few controls,  Volume, and Sync.  your only concerned with the SYNC button..

2. remove the old battery, and soldier your USB car charger directly to the old battery terminals.

3.  Flipp the unit back over and soldier wires directly to the sync button, The button should be covered with a foil shield, you will need to pry this away. The button once exposed should be divided into a positive and negitive terminal.  Soldier a wire to each terminal, leave enough wire to trail outside of your radios housing.    ANOTHER CAUTION NOTE.   SYNC YOUR BT WITH A DEVICE BEFORE YOU REMOVE THIS BUTTON, There is a change you can destroy the button trying to soldier to these terminals.


Leave enough wires trailing outside of your radio so you can affix extensions as needed.

STEP 6:

Powering the BT Headset.

I wired a secondary cup connector directly to my power point, then pluged the usb charger into that.  this way I can fully conceal the wiring inside my dash.

I used a on off toggle to power on/off my BT headset.

STEP 7:

Wiring the Snyc button so you can resync to new phones after you enclose your head set. into the radio.

I simply used a off/mom switch for this. 

afterwards install your radio, make your final solder connections, and walla... SYNC BT RADIO.

Comments

[JeanF57]

Hi all

Old post but new info. I'm in the analysis phase, I haven't done any hardware experimentation yet.

I've overview the SAA7706H spec sheet. (Note: I'm an electronic & software engineer).

.

Using the FLV, FRV pins is a bad idea because you're mixing 2 outputs pin together. Might damage either your SAA7706H or your auxiliary device over time.

Ideally, as mentioned by others, using the AUX input (pin 7& 8) would be the best. You will be able to use the volume, fade, balance and else...

You might need some extra resistors and caps (spec page 13 sect 8.1) to use the dedicated grounds (pin77 or 70). This is easy.

The challenge is having the SAA7706H to select the aux input. This is done through I2C (pin 56 to 58, SLC-SDA-A0). The AIC-audio input control I2C register (1FF8h) need the value 111b (07h) for AUX selection.

.

Either:

- Use a dirt cheap micro-controller with I2C, an 8 pins PIC or else, that only purpose in life would be to send this I2C setting on request.

- Or, by following the I2C lines, you might fall on a generic chip that will send this for you by simple manipulation. I suspect a free pin just waiting for its voltage to proceed. This chip should be connected to the radio's BAND/CD AUX button.

.

That's where we are now.

As my front speaker are also defective, I don't know if I'll fix them as well or change the whole radio. We'll see...

.

Keep us informed if you proceed on your side.

[AntonioW16]

What about the TEA6880H chip haven't found anything on that chip. Same radio though.

[JeanF57]

Hi Antonio,

.

I've quickly looked at the TEA6880H specs, especially the schematic on Page 6.

.

Beside the AM, FM and chime, there seems to be 4 input channels on this chip; A, B, C and D. D is mono, others are stereo. pin 14, 16, 18-22, 24 and 26. Again here, selection is done through I2C.

By using an oscilloscope, an headphone, an earpiece.. anything high impedance, you'll need to define these input and find an unused one. Something like A is for the CD, B for the tape, C for the aux...

.

You'll need also to do the steps for the I2C described above. Could have different registers and values, I haven't check.

.

Have fun!

[RichardC366]

I know I am very late to this party, but at looking at the PDF, as another poster mentioned, there are AUX inputs on the chip, I just dont know where to send voltage or ground to another location on the chip and what voltage to send to select the AUX. Have you figured this out?

[Balzackgoo]

I know this is an old thread but I just stumbled upon it looking to do a hack like this. My question is, why didn't you use Pin 7 & 8 on the SAA7706H chip? Those pins are labeled Aux_L and Aux_R inputs. Am I missing something?

[smithphi]

I noticed the aux jack modded into the front of the delco head unit as
well...I'm on the same hunt, looking at the SAA7706H for places to
connect an aux input (so I can play music from my phone). Does the aux
jack shown in the pictures have anything to do with this bluetooth
hack?

[mrfudd]

does anyone know what chip to remove to unlock a delphi 6-disk bose stereo for a chev silverado?

the head unit is mfg Oct. 2006 and is correct for the truck. I read a chip can be removed to allow it to work. the number for the chip in various sites does not match the numbers on the chips in my unit. can anyone help me? Thanks

[ST5785N]

I dont recommend bridging R and L channels. Produces an undesirable effect on the audio feed while using stereo and Cd. Highly recommended doing something along the lines of a 2 way splitter. Im still in the experimental phase, so bare with me.

[ineedit]

from what i can tell, you have this set up so that the aux only outputs to the front two speakers? is there a way to have it output to all four speakers?

[Railes]

simply bridge the front and rear, since my speakers in the front are blown out i only bothered to wire to the rear

[hamsammy]

Great idea! Good for you for diving right into a GM radio.

So is it just BT music? or talk too?

[Railes]

You can do talk aswell, i think a different bt unit would be perfered though. Trying to remove and solder to the traces under the microphone to bring it to dash level was impossible.