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markmark9125
markmark9125
Associate II
February 15, 2013
Question

Reset bus power

  • February 15, 2013
  • 2 replies
  • 791 views
Posted on February 15, 2013 at 20:48

I use my STM32F0 to communicate with an SPI slave device, which is powered by the 3V bus on the STM32F0.

My problem is that when I reset the STM32F0, the bus power is not interrupted, which leaves the SPI device in an unrecoverable state. I need to drop power to the device momentarily in order to re-initialize it.

Is there a way to forcibly disable the 3V power of the STM32F0 momentarily? If not, can you suggest an alternative solution? I tried powering the device from an I/O pin but it behaved erratically- it looked like the I/O pin was only outputting 500 mV.
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    2 replies

    Tesla DeLorean
    Tesla DeLorean
    Guru
    February 15, 2013
    Posted on February 15, 2013 at 21:37

    That the 3V is the input power rail, it would be hard to control. Some external regulators have an enable pin.

    The internal regulators can be switched off in STANDBY mode.

    External synchronous parts should have a reset, and you should have a POR circuit to reset them. Some POR solutions include a button or watchdog type reset.

    Are you sure you can't clock this SPI device out of it's odd state, or inquire with the vendor? Gate the supply to the SPI part?
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    markmark9125
    markmark9125Author
    Associate II
    February 15, 2013
    Posted on February 16, 2013 at 00:08

    Thanks for the help! I ended up powering the device off of one of the GPIO pins, which I know is generally taboo, but it only draws a few dozen uA, so it hasn't been a problem yet.

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