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My Teensy++ 2.0 is showing some slow fall times, around 1ms, when I set a pin to low (via DigitalWrite). It looks like there's capacitance on the line, but the rise time is pretty much zero, so that can't be it.

Has anyone had the same sort of issues? Is it possible that my Teensy is broken? I looked at the AT90USB datasheet but I couldn't find rise time and fall time on general purpose IO.

Thanks for your help!

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  • \$\begingroup\$ What does your circuit on the pin look like? How long are the lines, what are attaches to the output etc. \$\endgroup\$ – Trygve Laugstøl Jan 21 '13 at 20:03
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    \$\begingroup\$ Are you sure you aren't toggling the tri-state enable pin? ;) \$\endgroup\$ – W5VO Jan 21 '13 at 20:16
  • \$\begingroup\$ @W5VO ... you mean bit (i.e. DDRx.y) \$\endgroup\$ – vicatcu Jan 21 '13 at 20:37
  • \$\begingroup\$ @vicatcu Sure - whatever they call that pin on Atmel products... same concept with practically every microcontroller but everything is named differently \$\endgroup\$ – W5VO Jan 21 '13 at 20:39
  • \$\begingroup\$ @W5VO yea, pin makes it sound like it's configured in the 'real world' instead of 'in software' \$\endgroup\$ – vicatcu Jan 21 '13 at 20:51
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Turns out this happens when the DDR register is set to input instead of output.

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