To clear up any confusion about the number of colours available on the empeg display:

The Strongarm 1100 includes an LCD controller that the empeg makes use of. This basically allows a pixel to be strobed in hardware to emulate a shade of the constantly on intensity. The chip is actually quite clever and will look at the values of neighbouring pixels in order to determine the required strobe value for a pixel.

The empeg uses four of the hardware strobe rates to emulate the shades used on the display. These are as follows:

Pixel Value........Intensity..............Modulation Rate

0..................0%.....................0
1..................11.1%..................1/9
2..................20%....................1/5
3..................100%...................1

This provides us with a 2bpp palette, although a 4bpp palette with 16 shades is possible with the Strongarm. The 4bpp palette was dropped very early on in prototyping as it was found that the VFD (vacuum flourescent display) had very short persistence and therefore that the increased number of shades was both inneffective, and caused a dot crawl effect on animating an image using many shades.

The Prolux software incorporates a technique known as time dithering which increases the colour range over a period of time by calculating probabilities from the hardware intensity of a pixel value of whether a pixel should increase in value by 1 for a particular frame. I expand the palette to 8bpp when incorporating time dithering and thus 254 intensity levels (plus off and full intensity). The screen buffer is drawn approx every 38th of a second, and each frame drawn is drawn at 2bpp, so the effect can only be noticed over a number of frames.

Time dithering does however reduce the integrity of an image, and it is therefore preferable to stick to the 2bpp palette where possible, particularly when dealing with detailed images such as bitmaps, or where an image is moved around the screen.

Hope this clears up some of the confusion - Happy to answer any further questions on the topic, or any other empeg visuals/display related topic.

Toby