My HU is an older Alpine cassette with CD changer control M-bus (TDM 7534 10 years old) installed in my Supra. Prior to CarPC thinggy, I have a CD changer S600 connect to the HU. After CarPC installed, I use tape adapter for computer sound to the HU. That CD changer was never been use since.
I took the changer out and install in my Honda Accord original HU via one of the Adapter (PIE) I bought from Cruchfield. I also bought an Alpine M-bus to Aux adapter, but this thing doesn't work with the HU because the HU is OLD. To use this adapter, the HU must have an option in the setup to enable the sound in put from that adapter. This HU doesn't. I have to return it.
After I search the internet, I found some info on the Honda/Acura(older Honda/Acura use the same CD changer with switch Left/Right audio channel) forum saying that by using 3kohm resistor or 6V to foul the HU into "thinking" that the CD changer is connect to the HU and thus enable the sound from the changer port. So that when I hit the CD button on the HU, the HU switch to CD mode and the sound is feed from the PC.
Now what I don't know is how this 3Kohm resistor is connect to. Power Supply and DataBus? or ... ?????
CD changer connecto Pin out
The HU is similar to this.