0xbadcaffe

You are limited by how the board is designed.
You can configure an FPGA with a software application of your own design. Here's a nifty project that shows how: https://forum.digilent.com/topic/17096-busbridge3-high-speed-ftdifpga-interface/
Of course, there are multiple are multiple tools for configuration via a USB cable.. Vivado Hardware Manager, Digilent Adept Utilitites, etc.
Most FPGA boards have a button to accomplish the same thing.
You threw me off with the reference to reset. 

Hi @0xbadcaffe,
I checked with the other engineer who submitted the Digilent board files to the Xilinx Board Store; essentially, the .xdc files are not able to be added.
There was a much longer reasoning on why they couldn't be added / how the files potentially could be added but then we couldn't control if they got downloaded, etc. For what it's worth, Xilinx doesn't add the .xdc files to their own files on their Board Store either (https://github.com/Xilinx/XilinxBoardStore/tree/2022.2/boards/Xilinx) which lends to the idea that simply adding the files is not as straightforward as it might seem.
Thanks,
JColvin

Hi @0xbadcaffe,
Yes, that is entirely possible to do; simply just have the Rx assigned on one particular Pmod pin and the Tx on a different pin. An external wire like a breadboard jumper wire would be needed to make the electrical connection the two pins of course, but whether the Rx and Tx are part of the same UART core or not (or same board) doesn't matter.
So long as the setups are expecting the same baud rate and word length and the logic is in place to handle when data comes in at unexpected times (presuming you aren't using clear-to-send, etc, signals) it'll work. The harder portion is any extra application material to correctly process the data at more than one byte at a time (option 1 or option 2 style) to enable different types of functionality.
Thanks,
JColvin

Hi @0xbadcaffe,
The Pmod RS232 and Pmod RS485 can be used with the Arty S7 without any special crossover cables. This is because FPGAs can have their internal logic be "assigned" to any compatible IO pin (unlike microcontrollers or microprocessors where their UART or SPI cores are hardwired to only particular pins; the PIC32 microcontrollers that Digilent used to sell had a change in the architecture where the hardwired locations of the Rx and Tx pins changed).
Otherwise you could use the UART VHDL implementation that is used as part of the Arty S7 GPIO demo, https://digilent.com/reference/programmable-logic/arty-s7/demos/gpio; the UART_TXD port that is defined in the "top" file (in this case GPIO_Demo.vhd) is set to the corresponding RX port on the USB-UART interface in the .xdc file. This could easily be "assigned" to a different pin on one of the Pmod ports instead.
Let me know if you have any questions.
Thanks,
JColvin

Hi @0xbadcaffe,
Digilent does not have a demo using the both the Pmod RS232 and the Pmod RS485 (a singular design that seamlessly supports both devices would not be super straightforward either as the Rx and Tx pins on the two Pmods are on different pin locations on the 6-pin header).
I have made an external UART loopback on Digilent boards that takes serial terminal data from the host computer, sends the UART data out one of the Pmod port pins, receives that UART data via a breadboard jumper wire to a different Pmod port pin, and then sends the received data back to the serial terminal on a host computer. The general process of how to set this up in Vivado block design is described here:
The corresponding Vitis code that facilitates the described communication would be similar to this:
To be clear, this does not implement any of the control signals used in the Pmod RS232 and Pmod RS485, though otherwise are communicated with via standard UART.
Let me know if you have any questions.
Thanks,
JColvin

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