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Zybo: how to configure the PS to only use UART


Hi all,

    I am pretty new to FPGA design and wanna follow this tutorial(http://ece.wpi.edu/~rjduck/Microblaze MCS Tutorial v5.pdf) to create a "hello world" program through UART on Zybo.

    Basically, I wanna instantiate a microblaze MCS processor in PL and output its RX and TX signals to my laptop through UART.

    However, comparing Zybo with other board like Nexys4, there is no UART connection in XDC. (In XDC of Nexys4, there is TX/RX of UART connections.)

    For Zybo, TX/RX signals of UART is tied to PS MIO pins(read from chapter 6 of the Zybo manual).


    I tried to instantiate the ZYNQ7 Processing System and configure the "MIO configuration" part of this IP. I chose "UART 1"and selected IO to be MIO12/MIO13.

   Should I put MIO12 and MIO13 in the XDC file to tell vivado here is the ports for TX and RX of UART?

   Or I need to add some logic and configure "PS-PL configuration" in PS to connect the TX RX signals from microblaze to PS?


   I am stuck on this problem and any help is well appreciated!


   Thank you!




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MIO pins are in fixed locations and do need to to be specified in an XDC file. In fact, specifying them in an XDC file has no effect. In addition, you cannot connect programmable logic directly to the MIO pins -- they are owned by the PS7. You can connect the UART to your logic via EMIO. If the microblaze contains a UART, then you would need to cross over the RX and TX lines (like a null modem).

Alternatively, you can route the microblaze UART signals to a PMOD connector so that it is independent of the PS7.

Or you could connect the second PS7 UART via EMIO and null modem crossover to the microblaze UART and run minicom on the PS7 processor so you can see the serial output from the microblaze.

I do not know what you would like to do with your Zybo board, but it already contains a processor faster than the microblaze, so perhaps there is something else you would like to use the programmable logic for? There are many Zybo and Zedboard tutorials out there. Have you tried the Digilent Zybo tutorial?


More information about how you want to use the Zybo would help with suggestions on how to proceed.

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