AnsweredAssumed Answered

About not being able to get a desirable waveform

Question asked by IRON on Dec 10, 2015
Latest reply on Dec 17, 2015 by DaveThib

Hello all,


I have some questions


■Back Ground info

I am using ADAU1977(ADC), ADSP21489(DSP), and AD1934(DAC) in my system.

In the system, I am executing a "Talk Thru" Sample program.

However, during the execution, the output wave form from the DAC somehow becomes zig zag.(see attachment)

my guess of why this is happening is lack of the sampling rate on either ADC or DAC.(or both)


input signal : 1kHz sine wave.

sampling rate @ ADC : 192kHz

sampling rate @ DAC : 192kHz


I am am now doubting at the ADC register configuration(which I've done.)

(Reason: When I changed the FS setting on the DAC, the output from the DAC still remained to be zig-zag. I guess this is because the sampling rate of the ADC is insufficient.)



So, I also want you to focus on looking at the ADC registers' settings.

Could you please take a scan at the register setting?(see the attachment)

I want the 192kHz sampling rate @ ADC. Am I doing right?(I guess the sampling rate somehow became 20kHz in the attached pic.)


Not like the Hardware Reference Manual of DSPs, the ADC data sheet does not talk about sequence of register setting.

Do I have to take a special care for it?


Are there any possible causation that can lower the ADC's sampling rate?

(For example, a case in which I am not properly using PLL. )


Best Regards,

Yuta Mihara