2004 Honda Accord, Dual Climate Control, interface and Car-PC Touch screen control.
I initially started a thread on another forum around the time I started my final attempt to separate the Audio-Radio unit from the combined LCD display HVAC board (full Climate control system) in my G7 Honda Accord.
I have decided to post the updated design, circuits and info on the install here, this forum is more technically orientated towards circuit and microprocessor design along with Car-PC integration and it may be of more interest to a few in this forum. This is an unfinished project, but its getting close.
At this point it’s taken some time using the system to reach a final hardware – software design that not only covers everything I want now, but is also expandable to cover future ideas and needs. I have redesigned the hardware interfaces and designed a separate microprocessor unit for general vehicle IO interface.
After using the system with my basic $25 “Push Button-Rotary encoder” and reading up on BMW’s iDrive hardware-software control system, I have decided that this has a lot of merit in any vehicle application. I redesigned the hardware interface to allow for this and much more in the future.
New hardware has been installed and I have spent a lot of time drawing and documenting all circuits and connections. The complexity designing hardware interfaces, programming microprocessors and writing software for the Frontend Windows application is enormous – especially with a fully integrated control system with Climate control and vehicle systems hardware and PC interface.
I have finalised the circuit and layout for a simple standalone system. It allows you to remove the Accord Audio system and to interface and relocate the Climate control PCB. This allows full manual control of the HVAC with a small LCD display for HVAC temperatures and status. – NO PC needed
The system can be scaled up to full PC control and vehicle interface, which is the main focus of this thread.
Some circuits and layout follow.
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No one (apart from rumours) has successfully removed the combined “Dual zone climate control and LCD Radio 6 CD stacker unit” AND retained a fully functional climate control system. This last point is important.
Single zone (non climate control) systems have been removed with aftermarket kits. These basic systems leave a lot to be desired and work with of the shelf audio units. Basically a simple manual control of the basic single zone AIR-CON and a blank panel are supplied.
Dual zone “full climate control” systems are a complex system in any vehicle and unless the system has been reversed engineered correctly it performs poorly or not at all. Many owners who purchased replacement aftermarket integrated NAV-Audio solutions from China supposedly made for the Honda Accord G7 have found this out the hard way.
The problem is twofold.
1. The LCD display is made up of a number of fixed graphic display sections. A few are for HVAC temperature display and operational status. The rest display 6 CD stacker, AM-FM and Audio system information. The LCD module has over 75 connections to the PCB. Most people crack or shatter the module if they try to remove it without damaging the board.
The Audio – 6 CD unit mounts behind the front panel display PCB – This is a very large multi layer surface mount design board, size is 7” x 10” and almost as big as the front panel. It incorporates a large fixed segment LCD with all radio buttons, audio controls, LCD interface, key scan controller, HVAC buttons and HVAC microprocessor Climate control systems spread around the PCB.
2. The LCD display and front panel were designed primarily as a split part of the Radio-Audio system. The microprocessor interface that drives display data, power supply and control of backlighting and control illumination and all data clocking/strobe signals are coded inside the Radio-Audio unit.
The unit was obviously modified to take an undocumented single wire data stream (it took some finding) from the HVAC microprocessor and display it via the decoded/encode function in the radio.
There are no circuits (that I have been able to find) for the HVAC-LCD PCB or Radio – Audio microprocessor systems.
Removing the Radio-Audio system from the front PCB leaves you with nothing except a functional but blind Climate control system; and a very large PCB that had to be relocated if you want to use the space occupied by the removed Audio system. Doing so means that you no longer have any buttons or controls for the HVAC system as they are surface mounted on the main PCB behind the front panel.
Microcontrollers to the rescue.
Here is my journey to removing the existing system, fitting a CAR-PC and making the Climate control system fully touch screen integrated while retaining manual control for ease of use and for times when the PC or screen fails or are turned off.
Note: By integrated, I mean as good as or better than OEM in ease of use, response and feedback (display).
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The existing unit.
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Radio unplugged from the front panel.
Main HVAC-LCD PCB
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Here is the original layout in two formats.
Using a digital storage CRO I managed to identify a repeating data stream on an HVAC control line. Once all timing information had been calculated I set about programming a Microcontroller to decode this stream and send raw data to a USB port on the PC. I had the task of decoding the raw data and identifying which functions each bit in the stream 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 – just the temperature display.
And the basic modified proposed layout.
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The Display-HVAC PCB (7” x 10”) 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 me find a case and a location to mount it. I used an “off the shelf” plastic electronic case that is low cost and almost a perfect fit for the PCB.
The picture shows the new case with existing HVAC sockets protruding through bottom, just as the OEM unit did.
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The prototype PCB mounded in the case above the relocated HVAC-LCD PCB.
This includes sockets for the RS232 link to the Manual control Micro. The Car systems and USB interface.
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The “false” or "backing" fascia. The only item attached to this is the 8” touch screen and soon to be added Remote Manual Climate control buttons with small Microprocessor interface.
A padded panel covered to match the trim will clip onto this backing panel and follows the curves of the dash down to the centre console.
The backing panel mounts via the same three screw locations that held the OEM Audio/display unit into the top of the dash. The bottom is secured using two screw mounts that held the cubby in place.
I have incorporated the same holding mechanism as the OEM Audio unit utilised to lock the top vent panel into the fascia.
The backing facia is removed in the same fashion as the OEM unit. IE. Remove the top vent panel, remove the ashtray – or whatever they call it – remove the three top screws and the two lower screws and your done.
The Ashtray houses a number of USB sockets accessible when the lid is open.
This is a picture of the screen installed “roughly” just to get an idea of the usability of the HVAC when driving – It’s so nice to use.
The highlighted buttons indicate what functions are running in the same way as the OEM unit lit LEDS for Auto, Demist, Recirculate, etc. These screen buttons are lit by commands from the HVAC itself. I convert the existing LED signals on the HVAC PCB into data commands and incorporate them into the original HVAC coded data packets coming back to the PC.
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The PC is mounted in a Mini-Box metal case.
Size comparison to the old Radio-CD unit.
Screen: CTF800-WMSL - VGA 8.0" (16:9) TFT - Touchscreen USB
OPEN-FRAME (500 nits, LED backlight) -TRANSFLECTIVE PRO – Sunlight viewable.
Operating system: Windows7.
Load time: 11 seconds.
Shutdown time: 2 seconds.
Bios Initialisation time 15 seconds.
Standby to on time: 2 seconds.
Standby current: 240mA.
Motherboard: GA-H55N-USB3 5.5” x 5.5”
Support for an Intel® Core™ i7 series processor/Intel® Core™ i5 series processor/ Intel® Core™ i3 series processor in the LGA1156 package
1. 2 x 1.5V DDR3 DIMM sockets supporting up to 8 GB of system
2. Dual channel memory architecture
3. Support for DDR3 1666 (O.C.)/1333/1066/800 MHz memory modules
4. Support for non-ECC memory modules
5. Support for Extreme Memory Profile (XMP) memory modules
6. 4 x SATA 3Gb/s connectors supporting up to 4 SATA 3Gb/s devices
1 x eSATA 3Gb/s connector on the back panel supporting up to 1 SATA 3Gb/s device
Up to 8 USB 2.0/1.1 ports (4 on the back panel, 4 via the USB brackets connected to the internal USB headers)
Up to 2 USB 3.0/2.0 ports on the back panel
Processor: Intel i3 540 @ 3GHZ
RAM: 4 GB
Hard Drive: Solid State – OCZ 50GB.
Power Supply: M4-ATX, 6v to 30v input. 250 Watts - 300 Watts peak, fully Programmable.
The power/current drain when playing a movie is 36 to 48 watts – 3A to 4A.
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I ran into trouble with GPS sensitivity and DAB-FM reception. A search of CAR-PC forums revealed this to be a common problem and with users searching for an answer. The main problem is 12V ATX power supplies that need to provide full ATX output voltages when down to 6 volts input during cranking.
Because of the nature of GPS and the signal levels involved, any digital noise will desensitise or block GPS reception.
I came up with a solution which I have shared with others in the Power supply section. This involves installing the Power Supply (PSU) in a copper or aluminium case and filtering every input/output lead via a feed through capacitors.
This was the test setup with long leads. It worked and is now rewired and fitted in a case in the boot with the MB.
The second concession I had to make was to remove the PC from the dash and install it in the boot of the car. Noise from the PC was still enough to block GPS as the GPS receiver that comes with Garmin Mobile PC has no external aerial connection and besides, I wanted to fit this tiny receiver underneath the centre dash panel at the base of the front windscreen – Just behind the sunlight sensor for a no visible GPS installation.
After carrying out both mods the GPS has full satellite reception with the car sitting in the almost enclosed metal carport. FM reception from the rear glass mounted aerial shows no interference from the CAR-PC and PSU that are mounted a short distance away.
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Basic connections for a standalone (NO PC) installation.
Modified system with CarPC interface and Vehicle system interface micro.
Overall block layout of the system in the vehicle.
A high res version than can be zoomed.interface
Connections between the 2 microprocessors mounted with the existing HVAC PCB and the Manual remote HVAC controls micro.
Vehicle interface Microprocessor.
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Some Pictures of Frontend software.
Main Menu. Pushing the Rotary encoder button (soon to be iDrive) brings this screen up from anywhere, including if you exited to the operating system.
Because this system is fully controlled by the car controls and iDrive system, there is no need for navigation buttons taking up precious screen space when GPS, Radio, Audio screens etc are displayed.
The Big white/red button allows you to shut the PC down (after conformation) instead of having it automatically go to suspend to RAM mode when the vehicle is switched off.
UPDATE: Big white/red button removed and now made Automatic with the Hardware Auto/Manual button – see page 4
Climate Control. This is a full two-way transfer system with Highlighted buttons reading and reflecting the LED ports on the existing HVAC microprocessor. When a button is pressed, the on-screen button state and display only change when the HVAC responds with the new state. The system response time is virtually instant.
The Mode button on the steering wheel cycles through the main 4 applications (if they are running) and announces each application in turn. When the Climate control is displayed the volume UP/DN buttons change and announce the passenger temperature, the Channel UP/DN buttons do the Driver temperature.
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Menu2. Deals with non-essential programs and information not used when driving.
Steering Button calibration. I have manual OR fully automatic options to setup the voltage switching levels in this system. This allows for experimenting and expanding the system down the track