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.