A2B Slave setting in Forscan - A2B ACM Swap

[jbirdzee]

Hi All - on my 23 Pro I did a swap of my ACM so that I could get HD Radio AND have the digital audio (A2B) port that is used on the B&O system.

No issues getting HD radio working properly, and for the A2B - I customized the harness that comes with the PAC AP4-FD31 adapter so I can get HSCAN3, Power, and the clipping connections at the ACM to the PAC module since I do not have the factory amplifier wiring behind the rear seat. The end goal was to get an all digital audio path (replacement ACM->PAC AP4-FD31->Optical to aftermarket amp.

I can get the A2B audio working, the AP4-FD31 is working, my amp with optical audio is working.

The issue: when I adjust the volume of the radio, the 12" display gives a popup of the volume control but it does not update. I think I have narrowed this down to the A2B slave setting:

On my stock config the XX value is "00" but the ACM only seems to push out A2B data if this is set to "03". When it's set to "03", I get sound, I get volume adjust, but the screen doesn't update (I get a volume popup on the 12" screen but it just stays at the last number). When I set this back to "00" the volume popup updates properly but I get no sound. Kind of a crummy tradeoff. Any ideas?

I was thinking maybe I could leverage the changes that would be made if someone was downgrading from the 15" to the 12" display as they would have the B&O config and the smaller screen, but I haven't seen anyone go through that.

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[jbirdzee]

A quick update on this. A second change was required to make this work properly. In the APIM, SDARS HMI needs to be enabled.

So for anyone that swapped their ACM to enable HD Radio, and now wants to use the A2B port (It's a mini-usb connector on the rear of the ACM) to have digital audio out, you'll need to make the following changes:

ACM:
727-01-01 Xxxx xxxx xx from B to 3 (Enable Internal SDARS)
727-01-01 xxxx xxxX xx from 1 to D (Enable A2B Hardware and DSP)
727-01-02 xxxx xxXX xx from 00 to 09 (A2B Slave Configuration. I am not entirely sure what the different configurations do, because 03 also seems to work, but the 09 came from a 2023 platinum so I am using that)

APIM:
7D0-01-01 Xxxx xxxx xx from 0 to A (Enable SDARS HMI)

Hopefully this helps someone out there.