SC430 Video Introduction

The SC430 contains a 7 inch touchscreen LCD hidden behind a retracting wooden door.

This screen is an 800x480 transflective screen with dual edge backlights to provide enough backlighting to provide sunlight readability. In front of the screen is a complex polycarbonite plate that provide anti-reflection and polarization to further improve readability in the bright sunlight.

I have seen two types of touchscreens in the displays used in the SC430. The first is an IR touchscreen, which I have found in all three of the displays that I have. An IR touchscreen employs a matrix of IR emitters and receivers arranged in rows and columns. When a finger is present on the display, it interrupts the IR beam which is then translated into a position on the screen.

IR touchscreens are widely used in industrial controls for their ability to be used with fingers, pens, wrenches, or whatever. Hands can be gloved or not. It also allows for a much thicker material to protect the display. And finally, it is not sensitive to temperature like capacitive or resistive touchscreens. These, I believe, are the several reasons that it was chosen for the display in the SC430. They are, however, very expensive.

I have not personally seen a resistive touchscreen in an SC430 display, but I have seen several ads for replacement parts said to fit in the SC430. So perhaps it was used in later years. My 2007 IS250 contains a resistive touchscreen for example and I can attest to it being less responsive in colder temperatures and requiring more force to activate. An IR touchscreen requires no force at all. In fact, your tap is detected before your finger ever touches the display.

Video Interface

The multi-display in the SC430 uses an RGBs format video signal to display information from the navigation ECU. It also contains an unused and not very well documented composite input.

RGBs is just analog VGA like your computer uses, except for having a composite sync signal instead of separate horizontal and vertical sync signals. There are plenty of circuits available to combine the separate sync signals into a composite signal.

Another hurdle to simply using a VGA signal is the sync frequency. RGBs is really a standard television format (it is used in SCART, and was also common in arcade video games.) This means that the sync has a frequency of 60hz. VGA is typically 15Khz+ (depending on resolution). There are third-party software drivers that can change this sync frequency, but the result is unfortunately still a rather blurry sub-par display that makes text difficult to read. It is just like playing old console games on a TV.

Regardless of the above, even VGA is becoming obsolete. HDMI, DVI and MHL are the new norms for computers and modern video equipment.

So our first challenge is to explore our options for using these modern signals on our old displays.

One option, of course, is to replace the LCD completely. The advantages to this are that we get modern inputs, higher resolution, finer pitched pixels, increased viewing angles, and more even lighting and contrast ratios.

The disadvantages (or added challenges, if you prefer) of this approach are:

1. Losing the original video signal from the NAV ECU. Finding a display that can accept VGA and doing a conversion from RGBs to VGA is one possible solution.

2. Most LCD display controllers require button presses and menus to turn on/off, and control things such as brightness, etc.. This will not be directly compatible with the SC430. This could possibly be overcome by finding a display controller that allows you to write your own firmware or developing a complex system to translate vehicle signals to remote presses.

3. More complex in that you need to assemble your new display into the factory shell and interface with the original wiring.

4. You need to account for things such as sunlight readability and anti-glare.

5. If you want to use the original IR touchscreen, there is going to be some complexity to interfacing with it for your own purposes. This includes writing your own driver.

Bottom line is that this is not a plug-n-play drop in option.

If we are installing a CarPC, we are most likely going to be replacing the functionality of the NAV ECU anyway. I don't consider number 1 above to cause much sadness. Number 2 is still a challenge to overcome, however.

We are going to explore both methods in future articles in order to determine the best option. We will also be breaking this challenge down further.

SC430 Car PC Overview

I've been away from this project for so long now (and lost a hard drive with much of my notes) that I think I can begin again with a fresh perspective. In that spirit, I would like to get back to the very basics to begin.

A CarPC is the popular term for a user-installed and managed computer interface to the car. This was an extremely popular hobby back before infotainment systems were pretty much a standard in modern cars. Unfortunately, nearly every project was aimed at simply being able to play MP3s in the car and (in my opinion) that is what killed the hobby. These turned into very expensive MP3 players and not really much else.

The goals of a successful CarPC are to add convenience features for the driver/passengers and to expand on the capabilities of the car itself. It needs to integrate itself into the car and not be a distraction. And yes, it needs to play MP3s, but that should be its most minor function.

Some popular uses of a CarPC are:
1. Provide navigation for the user
2. Provide for multimedia playback
3. Provide internet connectivity to other users in the car and also to provide live information to the user

Before displays were common in cars, many people paid high prices for add-on displays to mount in their vehicles. Entire projects were often centered around this component by itself, including moulding custom dashboards.It was easily one of the most expensive components in the entire project. Consider, in 2006, I paid $600 for a flip out low-resolution VGA touchscreen in a single-DIN format.

But LCD screens quickly became a standard in many modern cars. The challenge then became to hack into this display in order to project our own content.

With modern cars containing built-in infotainment systems, I am going to break the new challenges down beginning starting at the very top level.


1. Power Control and supply
2. Video
3. User Interface and control (UI, touchscreen, buttons, knobs, etc.)
4. Audio
5. Integration

After this basic introduction, we will begin getting into the specific challenges as they relate to the Lexus SC430.

1. Power Control and Supply

This challenge includes integrating the power supply for your system into the vehicle system in order to not only supply the correct voltages to the various components, but to properly survive the harsh electrical environment within the car, and to power on and off the components along with the car.

2. Video

This involves determining how to tap into the built-in display and provide video in the format expected. It also involves discovering how to switch between factory video interface (if desired) and our own inputs.

3. User Interface and Control

This category involves determining how to interface with the existing user controls within the vehicle such as touchscreens, steering wheel remotes, dash buttons, radio controls, etc...

4. Audio

Establishing an auxiliary audio input in the vehicle as well as properly controlling the switching of audio sources and even outputs.

5. Integration

This category is wide-open and very dependent on what the user wants to do with their system. But the one thing required to overcome this challenge is to get to know the network used in your vehicle used to control the various components or if no network is present, to fully understand the wiring scheme of your vehicle in order to take control of its features.

Integration, of course, also involves making the system appear seamless and a part of the vehicle. Much of that is cosmetic. Some of that is software design.

It may also include determining how not to interfere with the original OEM system and to keep those systems available to the user.

So the above is a high level look at what is involved in developing a CarPC for your vehicle. While a very basic look, your project will wander if not broken down properly and the scope can quickly become overwhelming. The best approach to a project is to begin at the top level and approach each challenge individually, further breaking it down into smaller and smaller specific tasks. We will worry about integrating everything together at the end.

In the articles to come, we will begin to work through each one of these challenges as they apply to the Lexus SC430.

I am working on a large paper that will describe the entire vehicle network in detail. In the process of doing that, I will need lots of diagrams. I thought I would share a few of them as a preview to help understand the network as a whole.

Figure 1. AVC-LAN Network

First some clarification. The term AVC-LAN actually refers to a collection of signals.

• Two wire Differential Serial data based on NEC's IE-Bus protocol
• Video (in our case, it is RGBs, however there is a composite video available)
• Audio (Stereo, or mono in the case of the NAV and Telephone)
• Mute - Used to allow a component in the system to mute other sources of audio

We are mostly interested in the Two Wire Differential Serial Data signals. This by itself is an IE-Bus developed by NEC electronics. The devices are wired in parallel with one device acting as a 'hub' of sorts. In the case of the SC430, the Radio acts as the hub. It is the master in the system and the rest of the components will not operate without its presence. Do note the 60-80 Ohm resistor shown in the diagram within the H/U. From my research it appears that this is really all that makes something a master. If true (need to verify) the radio could be eliminated by a simple box with a resistor.

Take-Away: IE-BUS is connected in parallel in a Star topology.

 Let's the look at the rest.

 Figure 2. Entire Network

Figure 2 is a bit more complex, but accurately represents the entire network in the SC. The Network Gateway is capable of handling 3 BEAN buses, one IE-Bus, and one Debug interface (ISO 9141).

The BEAN bus uses a single wire and all devices are arranged in a ring (in series.) The various devices in the ring use an open-collector signaling in order to prevent interference on the bus when they are quiet. Bus arbitration is handled within the bus by buffering the signal coming in, adding its own frame, and then passing the data out. A priority code inside each message will determine the order of the signals. If the highest priority code is present in a message, the signal is just passed along and the device will add its own message after.

So how do we add on to this network, then? Well, there are two possible methods. The first would be to insert our ECU into the ring in series. The second is to use a buffer circuit to connect to the network in parallel. If you notice in Figure 1, the Mayday transceiver is connected using a buffer.  I am suspecting, but have not yet verified) that this only provides a read-only connection to the network. This should be fairly easy to verify.

I will be receiving the telephone computer and Mayday transceiver today. Included are several other components, one of those I am hoping is the buffer so I can verify the above. If not, I will need to pick one up ($35 on eBay.)

As always, much more to come...

Books and Links - Networks

I'm going to use this post to link to books and reference material that I have located throughout my research. As such, expect this post to be edited as I discover more information.

Books

Multiplexing and Networking (Progress in Technology) (1999) by Ronald K. Jurgen
This one contains 114 SAE papers, including all papers on the BEAN protocol. This book is out-of-print, so you will need to pick it up used.

Multiplexing and Networking Vol. 2 (2006) by Ronald K Jurgen
Contains 63 SAE papers covering networking protocols and technology between 2000-2005

SAE

 

ISO 

 

LINKS

Reverse Engineering the Vehicle's Networks

This is such a complex topic that I expect this category is going to get really messy. I'll do my best to mitigate that by putting together more concentrated information into the Papers section.

Essentially, what we are looking to do here is to take control of the various networks within the car. By why would we want to do that?

Well, let's talks about ECUs. An ECU is a computer inside the car. Your car has tons of them. I will be putting together a list of all the ECUs soon. But anyway, all of these ECUs are able to talk to each other which allows for the integration you experience in the car.

Just an example: When you open your hardtop, the roof ECU commands the door ECUs to roll down the driver and passenger side windows. It does this by sending commands over the BEAN bus (Body Electronics Area network.) The BEAN bus carries tons of information around the car containing sensor, switch, analog, and diagnostics data.

This networking concept reduces the amount of wiring needed in the car. Without out, the roof ECU would need several wires running throughout the car to activate the relays for the windows. With the BEAN bus, just one wire is used.

This network also makes expansion possible. Additional ECUs can be added to the system as 'Dealer Options' to provide more functionality to the car.

Unfortunately this is not very well documented and is going to require quite a bit of work to reverse engineer the system, but the ability to take control of the systems in the car and develop new functionality is a prize worth working for.

In order to do this, I will be building up a little 'test-bench' that involves wiring up some of the original components from the car. It will also require the development of some tools (hardware and software) to monitor and explore the network communications between the components. Once I have something stable, I can then install this in the car and from there, I can work towards unlocking all of it's secrets.

I have some parts I will need coming, so you'll be seeing a flurry of activity in the category.

Settling in!

I *think* I've got this blogging thing figured out and have things arranged mostly how I expect to use it.

<----- On the left, you will notice that there are a couple of menus.

The Category menu will take you to posts on certain topics. I am intending to use that to organize my posts by the various mods and information so that it is easy to browse for what you are interested in.

The Papers menu will include more formal papers and documents that I will write. Often, these will come at the conclusion of a project and will cover the mod from start to finish. Well, if I am not lazy anyway! This is also where you will be able to find technical information such as pinouts and other information.

I'll slowly be working to migrate much of the information I have posted in the forums and trying to flesh out each category. You may see some short posts in the different categories just to get them set up.

I have a decent sized google drive, so hopefully I will also be able to share files with you.

Welcome to the blog!

I purchased my 2003 Lexus SC430 in August of 2015 and soon after became a member at the ClubLexus forums sharing a great deal of information about my plans for customizing the car. As time went on, though, the posts became many and the topics more and more complex.

I started this blog in order to collect everything in one place and reduce the amount of load on the ClubLexus forums. Many of my planned modifications are very technical and perhaps the details are not as widely appealing.

This is my first post and I expect that this blog will change shape as things progress. So sit back and enjoy.

About the Car:

MY: 2003 (MD: 09/20/2002)
Mileage: 133K
Exterior: Twilight Amethyst  Metallic
Interior: ECRU (LA00)
Trim: 3P6
Options: Navigation, Mark Levinson System