Connecting TT 710 to car audio

[natoqc]

I would like to connect my 710 to my car audio (SAAB 9-5 MY 98 ) but I do not have a 3.5mm jack line in.

I do have a line-in possibility via a tel-in connector with audio mute through a SAAB specific wiring loom.

I am trying to fing out which connector from the 710 holder generates the signal trigger for the audio mute. On the TT 700 it was pin 7 but the 710 has a different pinout. Maybe somebody has the pinout for the 710 car holder.

Furthermore it would seem that the line out of the TT does not feed the telephone audio through this output. Is this correct?

[TonyHoyle]

I just built one of these.

Audio/power are of course already on connectors on the dock so you can plug directly into those.

Car mute on pin 14 (GP2) of the mcp23008 (which is the 20 pin chip in the car dock) - http://ww1.microchip.com/downloads/en/DeviceDoc/21919b.pdf

To derive audio mute you need to connect the TT output to the base of an NPN transistor (via a resistor, as usual. I used 1.3k), with its emitter shorted to ground.

The tricky bit is conecting to the pin, since it's an SMD. I used an SMD test clip (RS part no. 100-0348) which works, but is a bit hairy since it's not really a permanent connection... can't think of another way of getting the connection though as that pin isn't connected to the PCB.

Lights detect is on GP6 but I haven't connected that (it's probably a similar arrangement).

[TonyHoyle]

btw. this is connecting to a TomTom car kit module (that comes with the 700 PDK), which is ground to activate. You need to check the electrical characteristics of your saab connector and adjust accordingly.

[natoqc]

Tony, thanks for the response.

I was afraid the answer wouldn't be simple.
I'm not very conversant with electronics but am competent with a soldering iron. I understand your post but I would need a little more guidance.

Exactly what transistor should I use, would the following type be OK:
Code: BC107
IC max: 100mA
VCE max: 45V
VFE min: 110
Ptot max: 300mW

I presume I connect the C lead of the transistor to the car mute connector and as you mentioned the E lead (emitter) to the ground (SAABs are negative ground)

Any idea about the bluetooth phone audio not going out through the line out jack?

[TonyHoyle]

My transistor circuit is basically the same as figure 2 at http://www.rason.org/Projects/transwit/transwit.htm but without R2.

I'm no electronics expert by any means but it seems to me that the BC107 would do the job... I chickened out and used the same one on that page :p

[TonyHoyle]

btw. I think the phone audio not going to external speakers is a software issue - I've heard others mention it.

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