How can I maximize the UARTLite baud rate beyond 921600 baud?

[ivansavy]

Hello, I am using Vivado and Vitis 2020.2 to build a MicroBlaze application on an Arty S7 development board. At the moment, I have a 300 MHz clock routed to the UARTLite IP and have selected 921600 as my current baud rate. I've read in two Xilinx articles (https://support.xilinx.com/s/article/35903?language=en_US and https://support.xilinx.com/s/article/14760?language=en_US#:~:text=UART%20Lite%20can%20handle%20baud,rate%20will%20be%208%20MBaud) that I can set the baud rate to the AXI clock frequency divided by 16, though neither give a guide on how to do this. I'd like to set the baud rate to 2 MBaud, which is theoretically allowable for a 100 MHz AXI clock. Is this possible? Thank you

[zygot]

921600 baud is the highest value that most terminal applications will run at, and certainly if you don't use hardware flow control. FTDI has a terminal application for its USB-UART bridge devices and that only works up to 921600. I believes that this is the limit of the VCP driver capability that Windows wants ot use by default for USB serial devices. Of course you can do higher baud rates up to the limit of the bridge device which is 3 Mbaud or 12 Mbaud for H devices. For FTDI devices you need to use a different driver, write your own software application, and use hardware flow control. I've don't this but it's tricky. For a device like the FT232H 8 Mbaud is more practical.

I don't know how it works on MicriBlaze, but for a ZYNQ device you can set the UART baud rate in the board design ZYNQ subsystem block. I doubt that the Vitis console supports baud rates of 921600 as the SDK doesn't, but you can always use a different application for UART communications with your FPGA.

While high baud rates via UART connections seems to be desirable there are a lot of issues to address complicating real world application.

[ivansavy]

@zygot Thank you for the info. It seems like a baud rate of 921600 is already sufficiently high so I will just use this setting in my design.