diff --git a/demo/ledclock.c b/demo/ledclock.c index 712bab5..7a6f96d 100644 --- a/demo/ledclock.c +++ b/demo/ledclock.c @@ -1,17 +1,33 @@ /* - * Digital I/O example + * LED Clock demo * Part of Comedilib * - * Copyright (c) 1999,2000 David A. Schleef + * Copyright (c) 2001 David A. Schleef * * This file may be freely modified, distributed, and combined with * other software, as long as proper attribution is given in the * source code. */ + /* - * Requirements: A board with a digital I/O subdevice. Not just - * a 'digital input' or 'digital output' subdevice, but one in - * which the channels can be configured between input and output. + * Requirements: + * - A board with a digital output subdevice and a subdevice that + * can trigger on an external digital line. A parallel port + * satisfies these requirements. + * - A Fantazein LED Clock modified so that the individual LEDs + * can be controlled directly by the digital I/O lines. + * + * The Fantazein clock has 8 LEDs arranged in a row on a wand that + * sweeps back and forth at about 15 Hz. Unmodified, the firmware + * of the clock lights the LEDs at the appropriate time to print + * words and the time of day. Since the wand moves quickly, it is + * barely visible, so it looks like the image floats in the air. + * Stuart Hughes modified a clock so that the LEDs could be controlled + * directly by the parallel port of a computer, and wrote the + * appropriate software using RTAI to create a stable image. This + * is an attempt to port the demo to Comedi. + * + * It needs much work. */ #define _GNU_SOURCE