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ADS127L11EVM-PDK: How to used ADS127L11EVM with Teensy®︎ 4.0 Development Board

chirag bhavsar
Prodigy 10 points
Part Number: ADS127L11EVM-PDK
Other Parts Discussed in Thread: ADS127L11

I used Teensy® 4.0 Development Board for spi communication.

First i try to read or write the register of  ADS127L11 IC but when i try to read particular register value i got 0x00.

Hardware Side:

I give 5V on J12 in +Vin.

Attached JP4 jumper with 2&3 No pin.

Remove JP3 jumper.

Attached JP7 jumper with 2&3 No Pin.

Attached JP6 jumper with 1&2 No Pin.

firmware side:

I make Start and Reset Pin high.

I send 0x4C 0x00 0x00 frame in SDI.

  • +1
    TI__Mastermind 37760 points

    Hello Chirag,

    Welcome to the TI E2E community!

    When using the ADS127L11EVM with an external controller board, you need to provide both +5V to J12 (as you have described) AND also an IOVDD supply to J13.  IOVDD should be set to the IO voltage level that your external controller board uses, and can be in the range from 1.65V up to 5.5V.

    Also, when using an external controller board, the PHI board should NOT be connected to the ADS127L11EVM board.

    Regards,
    Keith Nicholas
    Precision ADC Applications

  • 0 in reply to Keith Nicholas
    Prodigy 10 points

    Hello Keith Nicholas,

    Thank you for your Fast Response,

    I want to read & write ADS127L11 IC register value so how many bytes & it sequence i want to send in SDI?

    Also how i got the converted ADC Value? can you please share me the byte sequence for this.

    For Daisy-Chain Operation which data frame i want to send in SDI line for get ADC Converted Value?

    please provide me example for this 

  • +1 in reply to chirag bhavsar
    TI__Mastermind 37760 points

    Hello Chirag,

    Figure 8-31 shows details needed to write to an internal register, consisting of 2 bytes of data.

    Figure 8-29 shows the details needed to read an internal register.  Reading an internal register requires two separate SPI frames, with each frame equal to 2 bytes (16b), when using the default power-up register settings.

    Figure 8-33 shows the details needed to read the 24b conversion result with the default power-up configuration.  When reading conversion results, wait for /DRDY pin to go low (can software poll this pin or connect to a MCU interrupt pin), then keep SDI pin low, and send 24 SCLKs (3 bytes).  If daisy-chain multiple ADS127L11 devices, then the procedure is the same, only you clock n*24, where n is the number of ADS127L11 devices.  If 2 ADS127L11 are daisy-chained together, you would send 48 SCLK and capture 6 bytes (48b) of data.

    We have ADS127L11 example code on the product folder page for more details.

    https://www.ti.com/product/ADS127L11#software-development

    https://www.ti.com/tool/download/SBAC296

    Regards,
    Keith

  • 0 in reply to Keith Nicholas
    Prodigy 10 points

    Hello Keith Nicholas,

    Now I am able to read and write Register,

    when I send NOP(0x00) on SDI pin it is responded with converted data,

     3 ADS127L11 is connected in  daisy-chained and if  i want second ADS127L11 converted Data then i send 6 bytes with 0x00 in SDI pin 

    this is right?same if i want  third ADS127L11 converted Data then i send 9 bytes with 0x00 in SDI pin? 

  • +1 in reply to chirag bhavsar
    TI__Mastermind 37760 points

    Hello Chirag,

    Yes, you are correct.  Total number of bytes to read is 3*n, where n is the number of ADS127L11 in daisy-chain.

    1.  Monitor /DRDY line, and when it goes low, set /CS line low.

    2.  For three ADS127L11 in daisy-chain, read 9 bytes total (send 9*8=72 SCLKs)

    3.  Set /CS line high to end the SPI frame.

    4.  Repeat steps 1 through 3 to read additional conversion results.

    Regards,
    Keith

  • 0 in reply to Keith Nicholas
    Prodigy 10 points

    Hello Keith Nicholas,

    Without monitoring of /DRDY line I got converted data when I send packet on SDI line and make /CS line low so this method is right?or I want to compalsary observe /DRDY line?

  • +1 in reply to chirag bhavsar
    TI__Mastermind 37760 points

    You always need to monitor the /DRDY line.  If you do not, then you can miss conversion results, or, if you read data before the next conversion result is ready, you will get incorrect data.