ADAU1467 TDM512 issues

Question

Hello, 
 I am using an AKM AK5538 ADC in TDM512 mode (schematic attached). The DSP settings for Serial In 0 are also attached. 
 BCLKO0, LRCLK0 are outputs into the ADCs BCLK and LRCLK. MCLKO goes to ADC MCLK. SDTO goes to SDATAIN0. 
 Unfortunately when attaching 8 level meters to the 8 inputs, I only see activity on channel 1 and 2.

Harishgowtham · Answer

Hello Sylwester, 
 I have a couple of questions, before that could you please help me with attaching your project? 
 I believe your sample rate is 48KHz. Note that you can't do TDM16 if the sample rate is above 48kHz. 
 Are you trying to input TDM16 to the DSP? I have to confirm once again since you set the serial input to be 16 channels and you mentioned TDM512 mode, below is what I found in the ADC datasheet regarding TDM512 mode. 
 
 Are you trying to do something like this above picture, having two 8 channel ADCs and cascading it to give a 16 channel ADC out to the DSP input? 
 Can you probe the ADC's SDT0 pin and verify it's outputting 16 channels? If possible, please attach a scope shot of serial clocks and data. 
 I see your word length is set as Flexible TDM (FTDM), I hope it's mistakenly set. 
 Sylwester said: when attaching 8 level meters to the 8 inputs, I only see activity on channel 1 and 2. 
 This channel 1 and 2 receive correct and intended data from the ADC? 
 There are only a very few registers to put the DSP in TDM16 and it will be running without out a problem once it receives 16 channels (of course with a proper clock settings), so we have to closely look at the ADC's out. 
 I haven't checked the ADC's registers yet; I will do once I get a reply from you. 
 Regards, 
 Harish

Harishgowtham · Answer

Hello Sylwester, 
 Your project is working fine for me, I tried giving TDM16 inputs. please look below. 
 when input is given when no input is given 
 
 I see that you set the serial input port as TDM16 and you made the DSP master, so the BCLK going to the ADC will be 24.576MHz, this clock (512*fs) is for TDM512 mode (which is a chained mode) but now you are only using TDM8 Out from the ADC (TDM256 mode in your ADC). Since you are using 8 channels out from ADC, you just try running your ADC in TDM256 mode (TDM8 out which is 256*fs = 12.288MHz BCLK), to do that just set the serial input port as TDM8 (8 channels,32 bit per channel), it will generate 12.288MHz BCLK and send that to your ADC. Then it will be running at TDM8 mode. 
 Sylwester said: They stay at -34dB when nothing is connected. 
 you disconnected the audio cable from the board, and it still shows -34dB? or did you stop playing the audio with the cable being connected? 
 Sylwester said: but the inputs never go to 0 
 when no input is there, the meters will not go to 0 (which is a full-scale value - 0dBFS is full level), rather it goes down like around -80dB etc.. 
 Did you probe the ADC out signals to see what it's sending? 
 Regards, 
 Harish

Harishgowtham · Answer

Hello Sylwester, 
 Sorry for the delay. 
 So now, you can get all 8 channels from ADC into the DSP without a problem, the only concern you have is that when you disconnect the inputs, the meter reads -34dB. Is that right? 
 can you send us the picture of your setup? 
 Regards, 
 Harish

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ADAU1467 TDM512 issues