Factory bluetooth / onstar w/ home-made system 2011 Silverado

[donbowman]

I'm in the midst of a Nexus-7 - replace - factory - radio for a 2011 Silverado project. I've scanned through the archives, but am not sure on one thing.

 

I have US8 radio, UE1 bluetooth/onstar option, UQ3 option.

(VIN 1GCRKSE36BZxxxxx)

I have gone through the 2011 upfitters guide, and it shows:

 

X1:

pin 4 "Voice Recognition Audio SIgnal (UUL or UUK with UE1)"

pin 4 "Cellular Telephone Voice Signal (UUL or UUK without UE1)"

 

ok, i don't have UUL or UUK, so i assume this is No-Connect.

 

X2:

pin 7: "Cellular Telephone Voice Signal (UE1)"

pin 15: "Low Reference (UE1)"

 

Now, what I'm hoping to find out before i disassemble and get a multi-meter out...

 

How would i know that the 'long-press' on my steering wheel controls has activated the microphone? Is it that pin7 of X2 is a line-in voice (referenced to ground), and pin 15 will drop low when a voice-call is started?

 

Or is this something that is signalled on the low-speed single-wire canbus/gmlan (pin 13 of X1)? I have the low-speed gmlan sorted out to get into the Android (to retain my steering wheel controls for volume etc).

 

E.g. i'm hoping to have:

mic->Onstar VCIM, run as factory, and get line-out (for the onstar voice prompts / far end of phone call), w/ some signal when the call starts/ends.

 

Since Android doesn't have headset profile ('server') i'm hoping to use the factory bluetooth but run it through the nexus and then to the amplifier.

 

(ps, the project came about after I got dissatisfied w/ one of the cheap 2-din android devices, I'm documenting my slow progress here).