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AD7771 and DOUTx interface

Category: Software
Product Number: AD7771

Hi,

I want to read ADC data from AD7771 via DOUT0 line - all 8 channels in 1 line.

What I did:

I am in SPI control mode:

- Set PowerMode to LP

- Set decimation rate (I want ODR = 1 kHz) => 1024/1 = 1024 = 0x400 - to the rigister  SRC_N_MSB I wrote 0x04 and to SRC_N_LSB I wrote 0, then I update it via register 0x64 (SRC_UPDATE)

- Set Output format and DCLK via reg. 0x14 (DOUT_FORMAT) => DOUT_FORMAT = 0b11100100 (1 DOUTx line,CRC header,reserved,MCLK/4,Reserved).

- Set reference to internal via reg. 0x15 (ADC_MUX_CONFIG) => ADC_MUX_CONFIG = 0b01000000

After that I can see:

- DRDY pin has period of 1 khz - perfect!

- On the scope I can see 8x32 bits packets - looks OK to me.

Questions:

- Is OK when after all 8x32 bits packet the CLK still generates cloks even if the data are already sent?

image here:

- Where does the data start (CRC header for channel 0)?:

Finally I tried to read this data by STM32 via SAI interface, but I am not succesful. The discussion is here without answer:  RE: Any advice on reading the AD7779 DOUT0 using an STM32 SAI input? 

Thank you for any advice.

Jan.

Top Replies

  • Hi   ,

    Regarding the data read using SAI- Attached below are the settings with which I was able to get the data read successfully

    Init:

    Details:{AudioMode = 3, Synchro = 0, SynchroExt = 0, MckOutput…

  • Hi  ,

    We will look into this. I will contact the product owner and get back to you. 

    Regards,

    JC

  • Hi  ,

    The CLK is free running so there will be extra clocks if Output data rate is low. You can ignore the clocks after 8x32 bits till there is another DRDY signal.

    The data start is on the first clock…

Parents
  • Hi   ,

    Regarding the data read using SAI- Attached below are the settings with which I was able to get the data read successfully

    Init:

    Details:{AudioMode = 3, Synchro = 0, SynchroExt = 0, MckOutput = 0, OutputDrive = 0, NoDivider = 0, FIFOThreshold = 0, AudioFrequency = 0, Mckdiv = 0, MckOverSampling = 0, MonoStereoMode = 0, CompandingMode = 0, TriState = 0, PdmInit = {Activation = DISABLE, MicPairsNbr = 0, ClockEnable = 0}, Protocol = 0, DataSize = 64, FirstBit = 0, ClockStrobing = 1}

    FrameInit

    Details:{FrameLength = 256, ActiveFrameLength = 1, FSDefinition = 0, FSPolarity = 0, FSOffset = 0}

    SlotInit:

    Details:{FirstBitOffset = 0, SlotSize = 0, SlotNumber = 32}

    Here it has been configured in such a way that SAI reads 32 slots, where:

    channel0 = (data[1]  << 16 ) | (data[2] << 8) | (data[3])

    channel1 = (data[5]  << 16 ) | (data[6] << 8) | (data[7])

    and so on.

  • Thank you!

    Now I can read the data by STM32!! BUT: I had to change some params:

    1) ClockStrobing to 0 - Data are sampled on Falling edge - datsheet page 9, Figure 2

    2) ActiveFrameLength to 128 - not exactly sure why has to be this value

  • Could you check if the DOUT_FORMAT[7:6] in the DOUT_FORMAT register (Address- 0x14) is set to 10 or 11 to get all data on a single DOUT line?

    Reference: Datasheet - page 74

    www.analog.com/.../ad7771.pdf

  • I set bits [7:6] to 0b11 

    Exactly this:

    uint8_t tmp = 0;

    AD771_ReadFromReg(0x14, &tmp, 1);

    tmp |= (1<<7) | (1<<6); //1 out line for all channels
    tmp &=~ (1<<5); //status header
    tmp |= (4<<1); //DCLK

    AD771_WriteToReg(0x14,&tmp,1);

  • Also I was probably in a hurry. I can read now only first 4 channels. But I'm pretty sure I could read all 8 channels - so had to change something else... 

  • Hi  ,

    I hope you have got answers for all the queries you had. Please confirm that you could read all 8 channels.

    Thanks

    Vikas J

  • Hi, unfortunatelly I can not confirm it.

    The best results  I have got:

    I Can read 4 channels or can read 8 channels but with shift: first byte is on second possition in my rxDataArray,... so I need to read not 32 bytes but 33. So I still do not have the right configuration, cannot find any detailed information about it

Reply
  • Hi, unfortunatelly I can not confirm it.

    The best results  I have got:

    I Can read 4 channels or can read 8 channels but with shift: first byte is on second possition in my rxDataArray,... so I need to read not 32 bytes but 33. So I still do not have the right configuration, cannot find any detailed information about it

Children
  • Finally!

    This variant works to me - reading 8 channels in 1 DOUt line:

    hsai_BlockB3.Instance = SAI3_Block_B;
      hsai_BlockB3.Init.Protocol = SAI_FREE_PROTOCOL;
      hsai_BlockB3.Init.AudioMode = SAI_MODESLAVE_RX;
      hsai_BlockB3.Init.DataSize = SAI_DATASIZE_32;
      hsai_BlockB3.Init.FirstBit = SAI_FIRSTBIT_MSB;
      hsai_BlockB3.Init.ClockStrobing = SAI_CLOCKSTROBING_FALLINGEDGE;
      hsai_BlockB3.Init.Synchro = SAI_ASYNCHRONOUS;
      hsai_BlockB3.Init.OutputDrive = SAI_OUTPUTDRIVE_DISABLE;
      hsai_BlockB3.Init.FIFOThreshold = SAI_FIFOTHRESHOLD_EMPTY;
      hsai_BlockB3.Init.SynchroExt = SAI_SYNCEXT_DISABLE;
      hsai_BlockB3.Init.MonoStereoMode = SAI_STEREOMODE;
      hsai_BlockB3.Init.CompandingMode = SAI_NOCOMPANDING;
      hsai_BlockB3.Init.TriState = SAI_OUTPUT_NOTRELEASED;
      hsai_BlockB3.Init.PdmInit.Activation = DISABLE;
      hsai_BlockB3.Init.PdmInit.MicPairsNbr = 1;
      hsai_BlockB3.Init.PdmInit.ClockEnable = SAI_PDM_CLOCK1_ENABLE;
      hsai_BlockB3.FrameInit.FrameLength = 256;
      hsai_BlockB3.FrameInit.ActiveFrameLength = 1;
      hsai_BlockB3.FrameInit.FSDefinition = SAI_FS_STARTFRAME;
      hsai_BlockB3.FrameInit.FSPolarity = SAI_FS_ACTIVE_LOW;
      hsai_BlockB3.FrameInit.FSOffset = SAI_FS_FIRSTBIT;
      hsai_BlockB3.SlotInit.FirstBitOffset = 0;
      hsai_BlockB3.SlotInit.SlotSize = SAI_SLOTSIZE_32B;
      hsai_BlockB3.SlotInit.SlotNumber = 8;
      hsai_BlockB3.SlotInit.SlotActive = SAI_SLOTACTIVE_0|SAI_SLOTACTIVE_1|SAI_SLOTACTIVE_2|SAI_SLOTACTIVE_3
    		  	  	  	  	  	  	  	  |SAI_SLOTACTIVE_4|SAI_SLOTACTIVE_5|SAI_SLOTACTIVE_6|SAI_SLOTACTIVE_7;

    Thank you all!