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
OSCILLOSCOPE
As
I mentioned, the LPC2138 (IC1) is the heart of
the system (see Figure 4, p. 53). I used the Keil
MCB2130 evaluation board with a soldered LPC2138,
a 3.3-V regulator, and in-system programming (ISP).
The investigated signal comes in from the BNC
connector (J1) to the internal ADC of IC1. The
DC component can be removed from signal via the
S1 switch. In this case, the potentiometer (R6)
adjusts the vertical position of the graph.
|
(Click
here to enlarge)
|
Figure
4—The oscilloscope’s layout is fairly simple.
The Keil MCB2130 evaluation board is shown
on the left. I didn’t include unused components
on the board. |
Other
components are used for control. R7 adjusts a
horizontal position. R8 sets a trigger level (a
voltage when the collection cycle should be started).
S2 through S5 are control buttons used for setting
the horizontal scale or calling the Store menu.
J3 selects the European or U.S. video standard.
(The position of jumper is read at power-on.)
Resistors R2, R3, and R4 compose the video DAC.
J2 is an output RCA connector.
The
optional analog inputs (Input1 through Input5)
can be used as voltmeters. For this purpose, the
firmware continuously measures these inputs and
displays the results on the TV screen. In this
version, the range of input voltages must be from
0 to 3.3 V because the supply voltage (3.3 V)
is used as a reference.
