Other Parts Discussed in Thread: CC8530,
I am developing a system using 4 CC8530 based slave microphones with a CC8530 based master. Both slave and master use the TLV320AIC34 codec. The slave codec is very under used. The system pairs up all four channels and each microphone connects with it own output at the 4 channel master codec . The four analogue signals pass into a mixer.
Image 1 shows the signal straight out of the Codec pin LEFT_LOP_A before the channel has paired with a microphone.
Image 2 shows the same signal when a microphone has paired with no acoustic input.
This image shows random noise of about 200mV p-p
Image 3 shows the same signal expanded to a 1us per division timebase
With the expanded timebase the noise bandwidth is beyond acoustic frequencies.
Image 4 shows the same signal with the paired microphone and acoustic microphone input from a whistle playing a 1.2 kHz note.
Texas recommend the use of a 20 kHz low pass filter to supress out of acoustic range signals in their data sheet SLAS538B.
I have tried incorporating such a filter using the TI PurePath configurator and coefficients generated using TIBQ.exe. I used the coefficients for filter 10 set to 20 KHz with a 48 kHz sampling speed
Custom setup option enabled.
The coefficients were entered into page 1 registers
N0= 0x6F95, N1= 0x6F95, D1= A0D5.
The filters were enabled in register 12 page 0
After reprogramming the CC8530 with the new configuration the output signals were unchanged. It looked like the new coefficients had not taken effect
