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RXD and TXD 150 ohm series resistors on the Prop Plug and Prop Clip — Parallax Forums

RXD and TXD 150 ohm series resistors on the Prop Plug and Prop Clip

kpadams3kpadams3 Posts: 1
in General Discussion
Hi,

I am assuming the 150 ohm series resistors for RXD and TXD on the Prop Plug and Clip are there to protect the FTDI232R pins from being connected to something they shouldn't be connected to. Otherwise, if the FTDI232R (or the FTDI231X for that matter) were on the same circuit board as the prop the series resistors wouldn't be needed.

Just checking....

Thanks,

Kevin

Comments

  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2017-02-13 00:25
    kpadams3 wrote:
    I am assuming the 150 ohm series resistors for RXD and TXD on the Prop Plug and Clip are there to protect the FTDI232R pins from being connected to something they shouldn't be connected to.
    They're there to prevent over-currents in a bus conflict condition in case it's plugged into a Propeller board that has P31 and/or P30 enabled as outputs.
    Otherwise, if the FTDI232R (or the FTDI231X for that matter) were on the same circuit board as the prop the series resistors wouldn't be needed.
    For the same reason, it would be advisable to include those resistors on the same board, unless other buffering options were utilized.

    -Phil
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