C5535 eZdsp and AIC3204 demo code

c_ 64

Hi,

I'm trying out the aic3204 demo code that came with the C5535 eZdsp example code package, but I'm getting some odd results. Instead of having the headphones and microphone connected to the development board, I have a function generator connected to the line in, and an oscilloscope connected to both line in and line out. The first part of the program, where a 1 kHz signal is being generated, works fine. But when the system is supposed to sample the line in, and replicate the signal on line out, I get the results as shown in the attached figured, where the yellow signal is the signal from the function generator (500 Hz), and the blue signal is the output from the development board. Any idea of what might cause the bad signal?

Thanks!

over 13 years ago

0 c_ 64 over 13 years ago

Intellectual 630 points

Hi again,

Looks like the signal got a lot better when I changed the MICPGA registers from 40 kOhm to 10 kOhm. But still, as the attached figure shows, there's a DC offset of some sort. Why is that? Also, the output signal looks a bit noisy. Could that simply be my test setup, or is this expected?

0 Hyun Kim over 13 years ago in reply to c_ 64

TI__Genius 14965 points

Hi,

You may remove mic bias at AIC to remove offset and you can add high pass filter to remove noise.

Regards,

Hyun

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C5535 eZdsp and AIC3204 demo code