Start
• Simple
Video Signal •
Video with the LPC2138 •
Video Algorithm •
Tricks Used
•
Vertical
Sync & Resolution •
Video for other Apps •
Oscilloscope •
Implementation •
Construction & Results
•
Generate Video •
Sources and PDF
SIMPLE
VIDEO SIGNAL
A
standard video signal is a sequence of sync pulses
and the analog waveform between them. When there
are two gradations of brightness, the signal has
three levels (see Figure 1). There are two basic
monochrome standards—RS-170A and CCIR (typically
called NTSC and PAL for their color varieties)—that
have different timings, lines per frame, and refresh
rates.
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(Click
here to enlarge)
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Figure
1—This is the structure of a monochrome video
signal. This project uses the simplified structure
of the vertical sync pulses (without equalization
pulses). The number of TV lines per frame
is even. |
Note
that the standard video signal has a complex structure
of sync pulses. Each video frame has two nonidentical
fields (odd and even) with a fractional number
of TV lines for each. Sometimes the structure
can be simplified (e.g., in the case of the identical
odd and even fields). Normally, the TV accepts
the nonstandard video format without glitches.
As
for generating the signal, the microcontroller
must be programmed to output both the video bits
and the sync pulses. This task was traditionally
solved by software, but such a technique doesn’t
produce enough elements in a TV line. Therefore,
you must integrate the other tasks into the video-generating
algorithm and calculate all of the durations to
avoid the probable artifacts and the synchronization
glitches.
