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MaaxBoard-RT: external power, decoupling diodes?

tjaekel

Does anybody know a bit of the schematics of the MaaxBoard-RT?

I want to power the board with external 5V, but the USB-C should be also connected.
The USB-C, actually, provides the power for the board. So, on the 5V J1 pins (p2, p4) should be the 5V power (from USB-C).

Is there a decoupling diode from 5V USB-C in a way, so that I can also feed 5V (with decoupling diode) from external?

external power on MaaxBoard-RT

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  • While powering the board with the USBC measure the voltage at J1.  If it's 5V then I would say that there is no diode.  Remember if a diode is present there would be a voltage drop so you might measure something like 4.35V at J1.

  • in reply to dang74

    I did this "trick" (which I know).

    It shows me this:
    Voltages on 5V pins are 5.04V (on 3V3 pins it is 3.26V).
    So, it tells me:

    There is NOT any diode (even with a Schottky diode - it should be 5V USB minus 0.3V).

    This is bad:
    I cannot power board with external power supply (conflicting with power via USB-C, not decoupled).

  • in reply to tjaekel

    Remains the question: if I would provide 5V on 5V pins, driving against the USB-C power - is there any protection in PC (on USB-C)?
    Or would I "damage" the laptop USB-C port?

  • in reply to tjaekel

    I was wondering that too.  I probably wouldn't risk a PC USB port myself though.  If the only purpose is to configure the  board with USB I wonder if it's an option to carefully  'dissect'a USB cable to expose the individual wires... and then cut the 5V wires altogether so that they don't make it to the board.  Read up first on USBC because I think there's some fancy 'handshaking'' built in to support the USBC connectors ability to be plugged in two different ways.  Also disturbing the cable in this manner could adversely affect the characteristic impedance and cause communications errors.

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  • in reply to tjaekel

    I was wondering that too.  I probably wouldn't risk a PC USB port myself though.  If the only purpose is to configure the  board with USB I wonder if it's an option to carefully  'dissect'a USB cable to expose the individual wires... and then cut the 5V wires altogether so that they don't make it to the board.  Read up first on USBC because I think there's some fancy 'handshaking'' built in to support the USBC connectors ability to be plugged in two different ways.  Also disturbing the cable in this manner could adversely affect the characteristic impedance and cause communications errors.

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