2020 Si Full Audio Rework

[bikejog]

Does RS485 carries some audio payload (eg Navigation sounds, system beeps etc)?

If that is the case, then we need some kind of signal processing and mixing. For most people is not acceptable to discard all the audio payload that is coming from RS485. The audison remote control cannot help unless we decide to keep the OEM Amp to handle the center speaker.

Arduino (or any other SBC) idea, is promising. The difficult part will be to mix the 2 audio payloads by programming the computer. Maybe I can give it a try…

We know for sure that Axxess AXDSPX-HN3 has already managed to implement your idea.

The RS485 signal itself doesn't carry any audio data. It's all control data and perhaps also carries the vehicle speed. Connector C where RS485 is housed does carries other analog audio data (nav voices, some beeps (HU keypresses), and engine sound on 2020 Si).

You do not need to write any DSP code to mix in the different audio yourself. I think just get a DSP that can accept SPDIF *AND* analog (or a combination of SPDIF DSP and LC6i or such) and just feed SPDIF2 and the analog audios from Connector C into the DSP and LC6i and it will just work. Just use the remote control that came with the DSP to control the tones and volume. See my post #30 above on possible problems with echo, however.

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[kostas]

The RS485 signal itself doesn't carry any audio data. It's all control data and perhaps also carries the vehicle speed. Connector C where RS485 is housed does carries other analog audio data (nav voices, some beeps (HU keypresses), and engine sound on 2020 Si).

Yep, that's true.

The problem narrows down to the commands of the RS485.
In my case, without volume knob (damn you Honda!), a remote control would be an upgrade.
So, what is left to figure out is only the mute and attenuation commands...

 

[Misa33]

Thank you, Kostas and bikejog for all that useful info.

@bikejog

Can you recommend a DSP device that can get SPDIF and analog input concurrently and attenuate or mute channels upon external command?

@kostas, @bikejog

If I understand correctly, you propose to control volume from the external remote that the DSP device provides. What about the steering wheel controls and the touch volume controls? Will they continue to operate as usual?

 

[kostas]

Yes, only control through the DSP's remote control. The spdif has constant volume (not altered by HU's volume control). I'll only miss the volume control from the steering wheel (but a knob is so easy to grab it while keeping eyes on the road ). The rest controls on the steering wheel will continue to operate of course.
Tomorrow I'll give a more thorough test of the SPDIF signal. Personally, I don't care about the navi audio (who uses the garmin??). It may be a bit easier to have a proper sound distribution (audio, HFL and beep) with an appropriate DSP. Let's see.....

I studied the Audison's user manual and my understanding is that it doesn't mix SPDIF and analog. It's either one or the other. If I got it correctly...

 

[bikejog]

Yep, that's true.
The problem narrows down to the commands of the RS485.
In my case, without volume knob (damn you Honda!), a remote control would be an upgrade.
So, what is left to figure out is only the mute and attenuation commands...

I think before you go too deep into this, the first thing you need to do is to verify if the HFL works with a third party DSP. One guy installed AXDSPX-HN3 and his HFL call mate experience really bad echoing problems. I'm not sure if he screwed up his installed or if Honda baked in some magic source into the HFL processing. Or if this has to do with the processing delay. I know the control msg for HFL is different so the DSP knows when it's in HFL mode.

Looking at the control msg, there seems (not 100% sure) to be an attenuation field, for all speakers except the center speaker, that's set to 0 during normal and a small value during navigation guidance and a higher value during voice commands. So that seems to match the muting logic chart posted by @kostas.

The nav and voice command muting logics can be implemented, in a roundabout way, by the below block diagram. You can use this (Amazon Product ) or an Arduino as the "Level Sense" The Level Sense mutes the amp when voltage is sensed at the Mixer output. Center channel amp must have independent volume control. When you have to give voice or nav commands, manually turn down the volume (or press MUTE steering button) of the "Other Spks Amps".

HFL is a different animal. Questions are

• Do you mind if it goes to all speakers? If you only want it in the front speakers, then you could possible sample, with an Arduino, the HFT Mute voltage in HU Connector C and if it's between 3-5V, then you know you're in HFL mode, but not sure if the voltage will be there for the duration of the call or just when the microphone is required.
• Is there a reason why Honda only routes it to the front speakers?

It would be much easier if you can find a DSP that can be controlled using an Arduino or another SBC

 

[bikejog]

@bikejog

Can you recommend a DSP device that can get SPDIF and analog input concurrently and attenuate or mute channels upon external command?

I haven't look into this area so I haven't any. However, you could build your own volume and muting device by using volume control and audio switcher ICs. Mechanical relays can be used for muting.

Or interface a SBC with something like this (Amazon Product) to control the volume. Problem is I don't know if it allows you set the volume directly or is it just volume up or down control only.

 

[Misa33]

I think before you go too deep into this, the first thing you need to do is to verify if the HFL works with a third party DSP. One guy installed AXDSPX-HN3 and his HFL call mate experience really bad echoing problems. I'm not sure if he screwed up his installed or if Honda baked in some magic source into the HFL processing. Or if this has to do with the processing delay. I know the control msg for HFL is different so the DSP knows when it's in HFL mode.

Looking at the control msg, there seems (not 100% sure) to be an attenuation field, for all speakers except the center speaker, that's set to 0 during normal and a small value during navigation guidance and a higher value during voice commands. So that seems to match the muting logic chart posted by @kostas.

The nav and voice command muting logics can be implemented, in a roundabout way, by the below block diagram. You can use this (Amazon Product ) or an Arduino as the "Level Sense" The Level Sense mutes the amp when voltage is sensed at the Mixer output. Center channel amp must have independent volume control. When you have to give voice or nav commands, manually turn down the volume (or press MUTE steering button) of the "Other Spks Amps".

HFL is a different animal. Questions are

• Do you mind if it goes to all speakers? If you only want it in the front speakers, then you could possible sample, with an Arduino, the HFT Mute voltage in HU Connector C and if it's between 3-5V, then you know you're in HFL mode, but not sure if the voltage will be there for the duration of the call or just when the microphone is required.
• Is there a reason why Honda only routes it to the front speakers?

It would be much easier if you can find a DSP that can be controlled using an Arduino or another SBC

I strongly believe that the reason that HFT is using only the front speakers is to stop echoing problems (created by dsp’s time alignment). I still can’t understand why Metra failed to deal with the echo problem. Maybe @vblue42 can help.

I agree that It would be much easier if you can find a DSP that can be controlled using an Arduino or another SBC but I am sure of the existence of such a device.

Maybe it’s easier to go the Raspberry/Hifiberry way and process the signal (attenuation/mute) based on serial port commands.

 

[bikejog]

Maybe it’s easier to go the Raspberry/Hifiberry way and process the signal (attenuation/mute) based on serial port commands.

That's a great idea if the Pi/Hifiberry can handle Honda SPDIF2. Otherwise, I think it would be overkill to use it to only process analog audio.

 

[vblue42]

I strongly believe that the reason that HFT is using only the front speakers is to stop echoing problems (created by dsp’s time alignment). I still can’t understand why Metra failed to deal with the echo problem. Maybe @vblue42 can help.

In my troubleshooting with Metra it was suggested to test with time alignment off. It didn’t help. Echo was still present. As soon as I removed the DSP and plugged the factory amp back in the issue went away. Metra was only able to midigate the echo through their testing by lowering the volume to a point that any phone conversation in the car was useless.

 

[kostas]

After searching about DSP or AMP-DSP, I discovered that products from Helix can mix SPDIF and analog inputs.

 

[bikejog]

After searching about DSP or AMP-DSP, I discovered that products from Helix can mix SPDIF and analog inputs.

There's also this https://www.minidsp.com/products/car-audio-dsp/c-dsp-6x8.

Some people were able to get the current volume level and display it on an 8-segment display using a Pi so it might be possible to control the whole thing using a Pi.

EDIT: The control/config interface is just USB HID so yes it's def possible to control the whole thing using a Pi. Easy to reverse engineer by simply sniff out the HID packets. However, without knowing the protocol, not sure how long it would take to complete a task such as setting the attenuation value for all 8 channels etc. And not sure if the SPDIF will be compatible with Honda's.

 

[Moeqasem]

I got my self a 2017 civic LX with NO backup reverse camera, I want to install the OEM one can you please assist me if it will be plug and play, or do I need a wire harness from the camera to the head unit taking into consideration that I have the 5' Inch regular screen not touch one (If YES) please advise the parts numbers and if you have an installation catalog.

 

[905User]

Would that AXDSPX-HN3 unit allow one to use the existing amp with a new deck?

 

[JT Si]

Would that AXDSPX-HN3 unit allow one to use the existing amp with a new deck?

No - it's application specific to replace the factory amp and receive the proprietary digital optical signal and auxiliary signals from the factory head unit to allow you to use other amps.

The factory amp (touring/upgraded stereo version) cannot be used with other head units.

 

[vactor]

just got my civic and i really appreciate the great info in this thread. if there are any updates to the hands free issues or solutions to volume control etc, i would love to read them. i also figured out that i believe the SPDIF connector being used from is made by Fakra. i sent them an email seeing if they could tell me what connector that is so one could buy the connector and make a PnP adapter to a digital male coax connector to plug into any DSP that accepts a coax digital input. cheers guys!

-v

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