ECE 4760: Laboratory 3

TV Digital Oscilloscope


scope You will produce a digital oscilloscope which takes one voltage channel input and displays the resulting voltage trace on the TV.
-- There will be a selectable timebase, a fixed trigger level and slope, run/stop, and a frequency calculation.
-- A video example of what you should see with input from a signal generator.
-- Note that timing is very critical for this lab. You will need to write compact sample and trigger code which will fit into the horiziontal sync interrupt.

-- Part of the grade for this exercise requires that you figure out how to insert samples 32 microseconds apart into each video line
and optimize voltage trace refresh speed on screen.


You will probably want to review the code examples given in Video Generation with AVR.
Use this example as a basis for your program.
You must uncomment the multfix routine or put multASM.S in the project source.

Build the video DAC shown below and connect it to the yellow connector on the LCD TV using clip leads and a RCA phone jack.
Note that you should remove the jumpers connecting D0 and D1 to the USB chip, circled below.

The scope will be AC coupled. Use the following circuit to isolate the signal source from the DC level required by the ADC.
I suggest setting Vref to Vcc. Because of the sample speed required in this lab, you will have to be sure the ADC prescalar is set to 1 MHz.


Write a program in C and (possibly) assembler for the microcontroller with these specifications:

When you demonstrate the program to a staff member, you should exercise all the scope functions and show that the time scales are accurately calibrated. One way to do this is to simultaneously display the output of the signal generator on your scope and on the Tek scope. Your program should not need to be reset during the demo.

Your written lab report should include the sections mentioned in the policy page, and :

Copyright Cornell University September 11, 2012