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dm6437 EVM SPI problem

Marta
Prodigy 30 points

Hello to all, I am working with dm355 and dm6437 EVM, and I am communicating both with SPI. So I configure dm355 as Master using SPI0 and dm6437 as Slave. I have a problem on the dm6437 side, I configure SPI so the enable pin (FSX0) is configured as an input, but without the dm355 connected, just using the dm6437 EVM I can see, with the oscilloscope, 1.4 volts in that pin. Does anyone know why am I having 1.4 volts on an input pin with NO input connected?? Thanks in advance. Best regards. Marta

  • 0
    TI__Guru*** 125430 points

    The pin would be high-Z when set as an input, so it would just be a floating voltage.  That pin should be driven/terminated with something so that it's not floating.

  • 0
    TI__Mastermind 41665 points

    This sounds very similar to another thread here (are you working together?), the FSX0 pin should be high impedance with a pull down at power up, so 1.4v just does not make much sense unless something else is connected or the multimeter is miscalibrated.

    Beyond this, perhaps the 1.4v reading is a result of the i/o buffer being powered down by default, though this is just a theory I am throwing out there based on these pins being unique in this case. Perhaps you should try modifying the VDD3P3V_PWDN register as discussed in section 3.2 of the datasheet to see if this has any effect.