Ultra96-v2 pin function assignment

Question

Hello All,

I'd like to as you if is it possible to change function assigned to pin (in Vivado I/O planning) related with MIO.

E.g. change assignment of user LEDs from MIO to EMIO.

Or do I understand something wrong and MIO connections are fixed and cannot be changed?

How constraint files affect those assignments? Can you elaborate about it?

Part of constraints for the board are commented out, there is information that they are applied by FSBL.

Where in FSBL can I find those constraints?

Thank you in advance for your support!

narrucmot · Accepted Answer

GPIOs wired to MIO pins are fixed. The MIOs assigned to the user LEDs (MIO[17:20]) cannot be changed to EMIO. However, in the current Ultra96-V2 Vivado design that underlies the PetaLinux BSP there are 30 bits of GPIO assigned to EMIO and constrained to the I/Os on the high-speed mezzanine connector. With careful planning and rearranging or removal of other peripherals these GPIO could be re-constrained to I/Os on the low-speed mezzanine connector (this might make it easier to connect to them for prototyping). Keep in mind, though, that most of the I/Os on the low-speed mezzanine are constrained to "standard" peripherals that are specified to be at certain locations per the 96boards "Consumer Edition" specification. If you don't plan to use the low-speed mezzanine with any off-the-shelf mezzanine card, or are designing your own mezzanine card, you are free to arrange the I/Os (and accompanying peripherals in the underlying Vivado hw platform) to almost anything you wish.

--Tom

bhfletcher · Answer

You can and should change the I/O assignments for the flexible things -- like the Low-Speed and High-Speed expansion slots. However, for the fixed peripherals, you should not change those I/O location assignments. You could modify the other I/O characteristics for your design, like slew rate and drive strength.

Bryan