The resolution of the display is 101x80 in landscape orientation. It supports to basic color modes, 8 Bit and 12 Bit. In the former mode, the upper three bits of each pixel form the red channel, the next three bits are the green channel and the lower two bits address the blue channel. In the 12 Bit mode, each channel is addressed by 4 Bits. The drawback of the 12 Bit mode is that two adjacent pixels are to be mixed and written to the display (3 bytes per two pixels). I implemented the 12 bit mode but never really tested it. YMMV. In order to save memory, colors are specified as 8 Bit in 8 Bit mode and 16 Bit in 12 Bit mode as compile-time option (_LCD_8BIT). Color specifications conforming two both modes can be done with the LCD_RGB() macro. The macro takes red, green and blue channel data in 4 bit each and converts it to the correct output color for the active mode.

The display is configured from LPH8731-3C.h. The pin configuration for the Atmel consists of the used port (PORTA,PORTB,...), the respective data direction register and the pin on the port for each signal. In case that CLK and DATA are located on the same port, the directive LCD_PIN_CLKDATA should be defined with the read pin of the port used for these two. This signals that the fast software SPI may be used. If hardware SPI is desired instead, the define _LCD_SOFT_SPI should be disabled.

The runtime initialization call is LCD_init().The init sequence is scripted to reduce code size. The delays in the LCD init are chosen according to the data sheet.

The orientation of the display may be configured at runtime on-the-fly. It is implemtented so that the user doesn't need to worry about coordinate transformation. The display will be adjusted to a new upper left corner, depending on the argument of the LCD_Orientation() call. Every drawing command is conveniently relative to the orientation-dependent upper left corner. The only thing to be taken care of is to swap the maximum width/height constants in the 90 and 270 degree orientations (see LCD_FillScreen() in the C-File). It should be noted that orientation changes affect the pixel write direction registers only. Hence, different parts of the screen may be painted with differently oriented text and graphics.

Apart from usual functions like LCD_FillRect(), LCD_Putc(), LCD_Puts() and of course LCD_SetPixel(), image drawing routines are available. LCD_ShowImage() assumes the image to be located in flash memory. The other bulk drawing option available is LCD_ShowLine() which writes a row of pixels to the display from RAM (or a column with changed drawing orientation).

For the compilation, tree files are needed. These include the driver C implementation and associated header file plus the font (font_ascii_6x8.h in my case).

In terms of data/code size and performance, this driver not only needs way less memory than the other implementation(s) I've found so far -- but is also significantly faster.

Initially, I wanted to write a real old-school intro for the display. Unfortunately, one other project came up where the display was needed for a real purpose. In the end, it fits nicely in a 1U rackmount enclosure.

So what was left of my initial experiments was compiled into a small video (embedded below). The first part of the video shows a redraw test in different orientations, where text and image are re-painted with each increment of the counter.

What follows are two classic effects: tunnel and rotozoom. Both were tested in Matlab, then re-written as MEX-File and when the results were satisfactory, I just dropped them on the Atmel. The effects can be switched via 9600 8N1 UART/RS232 interface, hotkeys: r,t,z.

Compilation: a Makefile for GNU make is included, assuming an available avr-gcc based toolchain. It is probably necessary to adjust the device and clock parameters for compilation (make) and programmer type (make flash).