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PCM1865: Problem with Clock configuration

Fengyuan LU
Prodigy 20 points
Part Number: PCM1865

Hi, TI Expert Team

I am a starter with Audio ADC PCM1865, and what I want to achieve is that using 2*PCM1865s in a arrayed audio recording system with 8CH TDM Mode. 

IIC Communication is now tested to be OK by writing and fetching(reading back) from 2 PCM1805 seperately.

My system is formed like this:

STM32H745 Nucleo Board, Connected to my custom made PCB containing 2 PCM1865s

SAI interface and  iic bus are connected together, power supply is tested to be good.

And STM32 Serial Audio Interface is properly configured with CubeMX

Sampling Rate: 48000 kHz 

Frame Length: 256bits

Frame Sync: 50% Duty Cycle

Program Routine (NOT REAL CODE) is shown as follows:

# Power Up Hardware

# Write 0xFE to Reg 0x00 (Reset)

# Write 0x50 0x50 0x60 0x60 to Reg 0x06 0x07 0x08 0x09 (Diff input)

# Write 0x43 0x01 0x00 (0x80 for second device) to Reg 0x0B 0x0C 0x0D (Set TDM)

After doing that, my problem is:

1:Data Out port shows data but measured to be a total mess with LA

2:so that i added "# Read All Regs" to my code and get the values of Status Regs from Debugging Session,which look like

3:I found that PLL is not locked, and system status is not correct either.

4:I checked the waveform of BCLK and FS with scope, showing 12.288MHz and 48kHz, Good.

5:I also tried to provide a 12.288MHz SCK from pin15(SCKI), but things doesn't change at all.

6:I also tried to configure the clock by cancelling clock detection and manully writing Regs 0x20-0x2D, but it doesn't help.

I have browsed the forum and checked issues about PLL, they are using Xtals to provide SCK, However,my application doesn't allow a crystal to be used with PCM1865 so that i have to run this device in slave mode and get system clocked by obtaining a signal from MCU interface.

i have also applied for PurePath Console3, but i can't generate a configuration with that tool.

Feeling confused, I have tried everything i can get access to and don't think i have done anything wrong by referring to datasheet, but it just wouldn't work. Disappointed

Gratefully, i am looking for help here and looking foward to a reply.

Having my RegMap if is needed

pcm1865RegMap.xlsxpcm1865RegMap_CLK_Manual.xlsx

  • 0
    TI__Guru**** 181021 points

    Hi Fengyuan,

    Sorry to hear that you are having trouble with the PCM1865!  We'll look over the reg map, but can you try shortening your cables between the boards?  You might be having cross coupling with the bound wire bundle, so try separating them a bit as well.

  • 0 in reply to Tom Hendrick
    Prodigy 20 points

    Sorry for the delay. I finally found that the problem is quite simple.I pull up the I2C wires so weakly that reg values are not correctly written at a 400 kHz bit rate. After pulling up with a 4.7 kOhm Res, it works and now gets perfect audio output. Thank you quite a lot. :)