EXPERIMENT 2

INPUT/OUTPUT

written by Neal Glover (nealglover@uky.campus.mci.net)
	   Anthony Reeves (acrv@msg.ti.com)
           Kevin Donohue (donohue@engr.uky.edu)
           University of Kentucky
           Electrical Engineering Department


REFERENCES

DSKD Starter Kit Manual

TMS320C31 Users Guide

TLC32040 Spec Sheets


EQUIPMENT AND MATERIALS

DSKD Starter Kit and Software

Personal Computer

RCA Jack

9 Vac power supply (for the DSK)

Signal Generator

Oscilloscope


INTRODUCTION

The purpose of this experiment is to learn how to use the Analog Interface
Circuit (AIC) in conjunction with the DSP.   An input sample will be taken
from the Analog to Digital Converter (ADC) of the AIC and output to the 
Digital to Analog Converter (DAC).This experiment will allow you to observe
aliasing effects on different signals, to learn to program using interrupts
and the AIC interface in preparation for subsequent experiments.

The program provided gets an analog input throught the input serial port and 
provides a digital output through the output serial port with the help of
interrupts which provide synchronization.The sampling frequency of the ADC could
be changed by setting specific bit patterns and the anti-aliasing filter and the
gain control in the AIC could  be enabled or disabled through specific settings.

The aim of the experiment is to familiarise with those settings and also to learn
to program using interrupts and accessing the peripheral devices.

PROCEDURE

1.  With the power turned off, connect your board to the prallel port on
    the computer. Connect the 9 Vac adapter to the board and plug into an 
    outlet. Turn on the PC and change to the directory containing the DSK
    software. 

2.  If so the DSK is connected and functioning correctly
    and you are ready to begin work. 

3.  Examine the initc31.asm program and try to understand its operation.
    Comments have been provided to show how the initialization 
    routine works.  Look through the data sheets on the AIC (TLC32040C).  
    
4.  To demonstrate how to utilize an interrupt service routine (ISR), 
    initialize the AIC to a 8 kHz synchronous sampling frequency, with 
    the anti-aliasing filter on, and no scaling.Modify the appropriate
    initc31.asm file to accomplish this. Since this same routine will be 
    used throughout the remainder of the labs you should fix this file so 
    you can simply use ".include initcXX.asm" in your source.  Or you may 
    copy this file and use it as the starting point for each experiment.

5.  A routine that will input data from the ADC of the AIC and 
    sent it back out to the DAC has been provided.The input and output will 
    have to be synchronized.  This is best accomplished using an interrupt 
    service routine (ISR).  What AIC registers are used to input and output data?

6.  Initialize the AIC for an 8 KHz sampling frequency, filter enabled, no
    frequency scaling, and synchronous operation.  With the anti-aliasing 
    filter enabled where is cutoff  (Fc) likely to occur? 

7.  Using the signal generator apply a sinusoidal voltage of approximately 
    1 Vrms at the input jack of the DSK.  Assemble and run the program 
    while observing the output of the DSK on an oscilloscope.   Vary the 
    frequency of the signal and record any observations.  Describe how 
    they are consistent with your understanding of filters and aliasing.

8.  Now disable the anti-aliasing filter,, run the program, and again record
    any observations.  Again, how are they consistent with your 
    understanding of filtering and aliasing?

9.  Increase the sampling frequency to 16 KHz.  Once again using a 1 Vrms sine
    wave repeat steps 7 and 8, recording any observations.

10. Now set the AIC to various sampling frequency values and scaling values
    to become more familiar with  its initialization. Verify that the AIC is
    operating according to the parameters.