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ADS8688EVM-PDK: Chip select is not getting low

Abishek V
Prodigy 175 points
Part Number: ADS8688EVM-PDK
Other Parts Discussed in Thread: ADS8688

Hi

We have connected the ADS8688EVM to AST2600EVB(Processor) through SPI interface. Even after enabling the drivers in kernel and in device tree, the chip select is always high. How should we bring it to low? Any other step we have missed here?

Thanks

Abishek V

  • 0
    TI__Guru**** 181751 points

    Hi Abishek,

    The /CS input to the ADS8688 is connected to J4 pin 7 with only a series resistor between the connector and pin 38 of the chip.  There is nothing on the ADS8688EVM that should be preventing you from toggling /CS low.  Please double check your hardware connections and verify that the output pin from your processor toggles as expected when disconnected from the EVM.

  • 0 in reply to Tom Hendrick
    Prodigy 175 points

    Hi Tom

    We have checked Hardware side. We have connected CS,CLK,SDI,SDO,GND from our board

    These are the changes we have made in dts file of linux repo in openbmc.

        #address-cells = <1>;
            #size-cells = <0>; 
            adc@0 {
                compatible = "ti,ads8688";
                reg = <0>;
                spi-max-frequency = <1000000>;
            };

     We have also enabled the drivers for ads8688 in kernel menuconfig

     Even after this, CS is high. There is no signal for CS from the host.

    Please suggest how can we resolve this issue

    Thanks

    Abishek V

  • 0 in reply to Abishek V
    TI__Guru**** 181751 points

    Hi Abishek,

    I'm sorry, but I'm not familiar with that driver.  Are you able to verify your CPU pin mapping?