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Altera_Forum's avatar
Altera_Forum
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11 years ago

pin assignment - unused GPIO pins

Hi there,

I´m using the GPIO pin header of the DE2 - 115.

I´m finished with the pin assignment, but there are several pins unused. But i don`t want to have them floated, so i want to define them.

I already read, that it is possible to connect them via 0 ohm resistor to gnd or Vcc. But in that case, they used a standard routing file from altera.

I cannot use this file, but i want to define the gpio pins completely, to avoid damaging the board and the connected module.

Is it possible to:

- find the unused pins automatically

- define their states, but without using them in the project

or is it necessary to include I/O pins in the project to assign the unused pins to a state?

Perhaps there is an other way to assign unused pins?

Thank you in advance.

kind regards

1 Reply

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    11 years ago

    You have two options;

    1. Define all pins used in a schematic as port in your top-level HDL file, and drive them with valid values.

    2. Use the device option to "tri-state unused pins", or "enable weak pull-up on unused pins"

    Given that a design may not use all FPGA pins on a device, I generally use both options.

    Run the scripts associated with this DE0-nano design

    http://www.alteraforum.com/forum/showthread.php?t=45927

    and you'll see an example of;

    1. A top-level design file that includes all I/O pins used on the DE0-nano board

    2. A constraints.tcl script that assigns all the pins on the top-level, and some default constraints (including the weak pull-ups on unused pins constraint).

    3. A synthesis script synth.tcl that automates the build.

    This approach allows me to create a new project by copying the top-level HDL and synth.tcl script, making a few minor path adjustments for the new project, and then synthesize a new design.

    I never have to worry about whether I have forgotten to assign pins correctly.

    Cheers,

    Dave