I have a board with a AIC3106 and C6747 (similar to the 6747 EVM). I have the codec's serializers connected back to the DSP and I'm using 16-bit samples. When inputting a 1kHz sine wave at -12dB, I notice that the sample values are all negative numbers nearly at the bottom of the 16-bit range, around -24,000 (as if the input signal to the codec has a significant negative DC offset).
I've looked at the input signal on the scope and it looks as I expect - a line level input sine wave at about 700mV peak to peak centered around 0 V. My sample values still represent a sine wave and the audio playsback fine (audible 1kHz tone), but for some reason they're all negative values. (For playback the DSP is just sending the read sample data back to the codec).
Are there any codec settings (register settings or circuit setup) that would cause all samples to be negative? I don't see all negative sample values on the eval board and the code on each is nearly equivalent. The only differences are some DSP peripheral setup and which serializers are being used.
Thanks in advance for any help.
