ADAU1701 - I2S interface with BCLK 32 FS
Hello my friends!
I am trying to get the ADAU1701 to work with a Bluetooth module which is only capable of providing a Bit Clock that is 32 x FS.
I believe the standart I2S uses 64 x FS for Bitclock. So normally for a 48 KHz, Bitclock would be 3.072 Mhz.
However, in this case, my Bit Clock is 1.536 MHz, which is dictated by the BT module working as I2S Master.
My lines are as follows:
BT Module I2S Master - ADAU1701 I2S Slave.
MCLK 12.288 MHz - OK
BCLK 1.536 MHz - ?
LRCLK 48 Khz
Stereo - 16 Bit Data.
How do I get the 1701 to work with it?
Thank you!
Audio Signal Processors
SigmaDSP Audio Processors
adau1701
Hello Nando.One,
I went into the lab with the evaluation board and connected it to the Audio Precision digital serial interface. I setup the Audio precision to output 16 bit data with 16 bit-clocks per channel. Then I put together the SigmaStudio schematic. I was expecting on having to do some creative clocking but it just worked as it was. This was one of our early parts so it looks like it does react to the LRCLK rising mid-frame which our newer parts do not. In this case it works out well. I setup the 1701 for I2S signals and the left and right channels came in on channels 2 & 3 where I expected the signals to be. I checked the levels and distortion and they all were fine.
You will have to connect the master clock out of the Bluetooth part to the 1701 when you want to receive those signals. If the Bluetooth MCLK signal goes away when there is nothing connected then you will have to figure out a way to change clock sources. You may get clicks and pops so muting would be advised.
Will you also be sending signals to the Bluetooth part? I think if you run the serial output port as a slave it will probably work. I did not test that.
I have an example file. I have to find out how to attach a file on this new platform for EngineerZone... :
Dave T
Dave,
First and foremost, nice to get in touch with you again!
Thank you for going to the lab and going through all that trouble.
In fact I am sending the BT MCLK to my ADAU1701 board. I will take a look at the clock synchronization and screenshot that for you. One thing I forgot to mention is that in I2S mode, as soon as I enable MP4 ans LRClk IN and MP5 as Bitclock in, the ADAU1701 quits working. I had on the schematic a sine generator directly tied to the DAC output in order to sense when the 1701 was working or locked up. With BCLK = 1.536 Mhz and LRCLK at 48 KHz, it just quits. Make that BCLK 3.072 Mhz and the 1701 is happy again.
As for the file, would you please send it over to me over my email? fernando306@gmail.com
Much appreciated sir!
Hello Fernando,
Make sure the MCLK is the correct frequency when you are using and not using the Bluetooth.
Dave T
Dear David,
I hope this message finds you doing well!
I just would like to update you. The culprit was actually the Bluetooth module firmware I was running. I appreciate very much your time and efforts assisting on this issue. Knowing that you successfully had the ADAU1701 working with 16 bit-clocks per channel made me look harder for other causes. Now I have my ADAU1701 running happy here too!
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