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ADS124S08: Data Reading problem (MISO Pin) with ADS124S08

Rahul Gandhi
Prodigy 30 points
Part Number: ADS124S08

Hi,

I have interface ADS124S08 With STM32F746 Controller. I have facing issued with register reading. I have checked on the CRO and Found that Whatever data i have sending its properly show on the MOSI Line but MISO Pin did not response .

Thank 

Rahul G.

  • 0
    TI__Guru** 113765 points

    Hi Rahul G.,

    Are you interfacing to the ADS124S08 on the EVM?  There are some common issues that prevent customers from properly communicating to the ADS124S08.  First, all power supplies must be at nominal operating voltage (AVDD, DVDD and IOVDD).  Second, the RESET pin must be pulled high and not left floating.  The CLK pin must be tied low to use the internal clock or an external clock must be provided.  CS must remain low throughout the entire communication transaction (CS cannot toggle between bytes).

    Best regards,

    Bob B

  • 0 in reply to Bob Benjamin
    Prodigy 30 points

    Hi Bob B,

    Thank You for replay.

    Q: Are you interfacing to the ADS124S08 on the EVM?

    A: Yes

    All power supplies is stable and as per the requirement. RESET Pin also pulled high using CPU. I have checked CLK Pin on the EVM and J6 Connector is DNP and also pin pulled down by 470K(R74). 

    So please provided any other possible solution as soon as possible because we are struck with spi interfacing.

    Thank You,

    Rahul G.

  • 0 in reply to Rahul Gandhi
    TI__Guru** 113765 points

    Hi Rahul G.,

    It is best if you power the EVM board using the USB connector on the EVM.  This ensures that the power routing is as expected.  This also requires that a jumper be  installed at JP1 located on the right-hand side of the board.  Installing JP1 holds the onboard micro in a reset state and also disables the interface from the micro to the ADS124S08.  Then connecting the external board to the EVM only requires a good ground between the boards, and the digital pins as appropriate.

    As far as the SPI is concerned you will need to make sure that the SCLK speed is within the required clocking range of the ADS124S08.  I would start out with 1MHz to overcome any capacitance issue in the wiring.  MISO connects to J3 at SDO, and MOSI connects to SDI.  Make sure that the communication holds CS low throughout the entire communication transaction.  This requires that CS be controlled by a GPIO and not the SPI peripheral as the peripheral will toggle CS between bytes (or words).

    The SPI should be set up so that the data changes on the rising edge and remains steady on the falling edge of SCLK.  SCLK dwells low.  When reading register data, the commands are written to the TX buffer in your micro to initiate the SCLKs to the ADS124S08.  But the data coming from the ADS124S08 requires you to send (write) NOP (0x00) bytes to initiate the SCLKs for the ADS124S08 to send out data.  If you are still having issues, then send me scope or logic analyzer shots of the communication and a picture of your setup.

    Best regards,

    Bob B