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Original question:

ADS7253: SPI interface Question

ADS7253: ADS7253 Write/Read issue

Sachin Dighe
Prodigy 70 points

Part Number: ADS7253

Hello There,

We are using ADC Part No# ADS7253IRTER. The ADC is connected to MCU/DSP processor on the SPI Port. The MCU/DSP processor support the standard SPI Mode 0, 1, 2 and 3. The ADC samples the data on SDI line and shift out the data on SDO line at falling edge of clock. We have tried all four Modes of SPI to Write/Read ADC but no success.

Please suggest configuration for MCU/DSP to Write/Read ADC

  • 0
    TI__Guru 68326 points

    Hello Sachin,

    Thank you for your post.

    The ADS7253 does not follow a conventional SPI Mode. As you can see in Figure 1, SDI is updated on the rising edge of SCLK and latched on the falling edge. Meanwhile, SDO is updated on the falling edge. Typically, these devices interface with an FPGA or a controller which allows for precise timing of the SCLK edges to latch the data.

    If your MCU must use one of the standard SPI Modes, one solution would be to add a flip-flop circuit that "reclocks" the data. Please see Luis' response in this related post:

    e2e.ti.com/.../1797162

    Best regards,

  • 0 in reply to Ryan Andrews
    Prodigy 70 points
    Hello Ryan,

    As per your suggestion we have added positive edge trigger D-flipflop at the output of SDO_A pin and SPI clock is configured for 1MHz, CPOL = 0 and CPHASE = 1.
    But with these settings we are not able to get proper response for CFR read operation.
    Following is sequence for CFR read operation from our SPI driver

    Sequence of operation :
    Write CFR register (0x804000000000)
    Read CFR register (0x300000000000)
    Dummy sequence (0x000000000000)
    Note : Slave select pin made high and then low before starting every sequence mentioned

    after dummy sequence command in response we get data as shown below (in hex):
    0 0 20 a0 0 0

    Please help us to understand if there is any missing configuration from our side

    Regards,
    Sachin Dighe
  • 0 in reply to Sachin Dighe
    TI__Guru**** 182601 points
    Hi Sachin,

    Since this issue is being worked off line, I'll close the post for now.