Replacing the HVAC-Audio-CD in Gen 7

[MikeCz]

For anyone interested here is a lot more information on the Audio-6CD and HVAC unit and the problems and a possible solution to replacing the OEM Audio-6CD, especially if you are into DIY and not afraid to get your hands a little dirty.

Original Post - driveaccord.net/forums/ I decided to revisit this project and make sense of missing circuits and block diagrams.

Last time I dismantled the unit I managed to identify most of the IC’s on the main PCB. Specifically I identified the LCD Controller IC. After looking over the sockets and pin assignments on the main PCB I was starting to get really @#&^% off.

They have placed the display CPU inside the Radio. This drives the LCD data-clock, data-stream, control lines AND the key-scan controller for all audio control to and from the display Driver/Key-scan controller and LCD display circuitry located on the main HVAC PCB.

If you try to relocate the HVAC PCB, you will lose the LCD display and button functions when you unplug the radio from the HVAC board. It appeared that key-scan functions for all buttons on the HVAC PCB were built into the Display controller. If so, you may lose control of the HVAC if HVAC buttons are scanned through this device.

I discovered that an Air-conditioning data-stream is fed into the Radio unit – This is information about the current control state, settings and all diagnostic data and is decoded and then re-encoded in the Radio before being sent to the HVAC PCB and displayed on the old LCD.

Using a digital storage CRO I managed to identify a repeating data stream on this control line. Once all timing information had been calculated I set about programming a Micro-Controller to decode this stream and send raw data to the USB port on the PC. I then had the task of decoding the raw data and identifying which functions each byte or bit controlled or indicated. This has been accomplished and the picture shown is an actual screen capture of the basic display software I wrote running on the PC. - This has not had HVAC controls added at this time

In Short – The radio and CD can be removed and all HVAC functions can be retained.

[MikeCz]

Existing layout

[MikeCz]

Mod Layout

[MikeCz]

[MikeCz]

There will be more to come and a full DIY if there is any interest in this.

I have made a “one piece” aluminium face plate/panel that replaces the existing Head unit and lower cubby. The HVAC PCB will mount in the same position behind an 8” LCD screen. No need to cut or modify any HVAC plugs or leads. All HVAC function can be controlled from the touch screen on the PC.

The Car PC will mount below or in the lower cubby area. The lower area could hold the HVAC PCB if you wanted to add an AUDIO unit only in the top section.

A small $12 LCD display can be mounted in a convenient location if you wanted full time HVAC display of settings without running the CAR PC.

[MikeCz]

I have the full CAR-PC HVAC controls working. I will make this small interface available when finished, parts are about $50.

Basically:

1: Remove the radio and CD.

2: Remove the large printed board that they plug into and place and mount this PCB in a plastic box. The box is mounted low down behind the lower cubby.

3: The existing HVAC wiring is plugged back in – no changes needed - and a small micro PCB is mounted inside the case and a few wires are attached to the HVAC PCB.

Now, the only other lead that’s plugged into the relocated box is a USB cable going to the CAR-PC.

I have just finished the CAR-PC, same size as the old CD/Radio, it boots Win7 in 11 seconds. It cold boots from suspend to RAM to fully running in 2 seconds – Faster that I can put my seatbelt on and start the car.




In HVAC diagnostic mode all errors are decoded and reported with full error descriptions. Both diagnostic modes are supported and decoded.

[Grohe]

Definitely interested in this

[MikeCz]

Originally Posted by Grohe

Definitely interested in this

Hi Grohe, it’s starting to come together, getting to the last measurement stages now that the PC is built and I know the final size of all components.
I just finished mounting the 8” screen and I’m in the process of mounting the relocated HVAC PCB behind this new screen

The beauty of this design is that the original system can be put back together and installed if the car is to be sold. This is why I didn’t want to cut into the original Radio/CD unit fascia.

As before, if all you want to do is to relocate the HVAC PCB and put a new Radio/CD unit in the dash, then the small interface board I’m making will allow you to have a small display for the HVAC located in a convenient place.
This was the main stumbling block for a lot of DIY owners - In the past, if you removed the radio you lost the HVAC display.

I’ll make a full step by step write up with pictures when I’m finished. If there are a few people interested in the interface I may get a 20 or so interface PCB’s made up.

[MikeCz]

We have Separation.

There were a few setbacks that turned out to be a blessing in disguise.
The Display-HVAC PCB will not fit back into the console if it spaced back even slightly.

Honda made this board to just fit in the opening and the opening get smaller with depth.

This forced my hand to find a case and a location to mount it.
I found an “off the shelf” plastic electronic case that is low cost and almost a perfect fit for the PCB.

The picture shows the case with the existing HVAC sockets protruding through bottom, just as the OEM unit does.

[MikeCz]

The Prototype interface PCB is shown in the second photo.
There are only 3 leads coming from the case, the two original HVAC plugs and one USB lead to the PC.
This Interface PCB only has a handful of components and is very easy to build- all the hard work is done by the program code in the micro.

This case fits perfectly in the lower compartment behind the cubby.
No leads are changed in the car - The HVAC plugs back in as before for a perfect fit.

The only unused cable, at the moment, is the old Radio plug.
This will be utilised for the car PC or aftermarket audio system if you want to go that way.

The software controls the HVAC perfectly via the interface module.




The Prototype interface PCB
This Interface PCB only has a handful of components and is very easy to build



This was the old combined Radio/HVAC unit - You can see the green HVAC plugs in the photo.

[MikeCz]

Today was the first test of the relocated HVAC board and the A/C. Up until now everything was just data from the HVAC. Nothing actually connected to the CAR




The PC is mounted in a Mini-Box metal case. The case is beautifully made and around $60.




Here is a size comparison to the old Radio-CD unit.

[MikeCz]

Things were going so well as everything came together so easily, I was sure there was going to be a problem, but it all worked faultlessly first time.
There were no glitches or problems with the system as the car was cranked over. PC control of the HVAC was as smooth as silk.
PC automated diagnostics worked perfectly, no more remembering diagnostics-mode key sequences or trying to decode lit segments of the display.




HVAC mounted in the car.



HVAC - PC and 250 Watt programmable PSU in the car.

[MikeCz]

The HVAC PCB does not need to be removed to make changes to the firmware in the Micro, should the need arise.

I wrote a boot-loader into the firmware. A companion APP on the PC can
update the firmware at any time via the already connected HVAC-control
USB connection.





The PC slides down and locks into the existing side mounting tabs. The PC case is metal and has a wedge piece of hard foam glued to the bottom of the case.
As the PC slides down, the foam forces the new HVAC BOX to seat firmly against the existing rear mounting plate.
The PC is also secured by two screws in the plastic top mounting frame. No rattles and everything is locked in place.

Nothing had to be cut or modified in the car.

The Screen and PC are easier to remove that the old Radio/HVAC head-unit.

[Situationz]

looks like a well thought out plan is taking shape. great work.

[stiller fan]

i wanna see what it looks like when complete....