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Using a CRT Monitor

The data is transmitted by a CRT monitor by setting select lines to white and the rest to black. A CRT draws on the screen by one pixel at a time from left to right and top to bottom. They are redrawn fast enough to make it look like a complete image, however the watch can detect when a white line is drawn, or when a line isn't drawn. The screen starts out with a white line followed by up to 8 white lines for the first byte. Each line is either on or off transfering a 1 or 0 bit. The model 70 watch sends one byte for each screen refresh, the other models send two bytes per refresh giving them a total of 18 possible white lines per screen refresh..

What follows is an example of what you would see on your screen while the data is being sent. It is an mng image and not all browsers have support to be able to display it. The actual data transfer would take up the entire screen.
MNG support required

There are two sets of synchronization lines before the actual data is sent.
sync 1 sync 1
Sync 1 Sync 2
Here are some examples of the data.
data1 data2 data3 data4 data5 data6 data7

Using an LED

Essentially the watch sees the monitor as distinct pulses, at least distinct enough for it to interpret it as data. Displaying lines to a LCD monitor (or laptop) will not work because active matrix LCD's don't refresh, the pixels are always on or off. For computers that don't have a CRT some other method must be used. One method is to use a LED that is hooked up to a serial port, to transfer data by it flashing. The serial LED that Timex makes is not supported with this software, but there is a schematic included in the doc directory of the source code If you do build the schematic don't expect it to work with the windows timex software. Someone else made the schematic and the driving software, I haven't tested it yet so I can't claim it will even work, but I welcome e-mail from anyone who has.

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$Date: 2003/04/15 01:00:44 $

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