Raw pins for UART?

[ttrostel]

So this is probably well known somewhere so ...

If I want to use CMOS 3.3v pins for TX, RX etc from the Uart Lite for my Arty board .... say one of the PMOD ports, how do I get that connected?  I'd also like to do SPI etc etc the same way.

The default seems to want to drop it to the USB FTDI chip ... I think .... I'd like to go straight to something like an RS422 differential transceiver or such.

 

Thanks in advance.

 

Tom

[D@n]

You mean ... you'd like to go from something like a PModUSBUART straight into the Arty?

Have you looked at the OpenArty project at all?  While it is a project in progress, all three USB ports are already working.  (FTDI, PMODUSB, and GPS)  This project takes the bottom PMod port of JC and connects it to a PModUSBUART.  This includes not only the connections themselves (found in the XDC file), but also the logic to run the USB ports.  The logic used is straight 3.3 LVCMOS logic.  The RTS/CTS pins have, for the most part, been ignored.  Still, you might find the design instructive.

Dan

[ttrostel]

Can I do the same thing but with the axe_uart lite?

[D@n]

I don't see why not ...

Dan

[jpeyron]

Hi ttrostel,

I was able to generate a bitstream with this design. In addition i needed to have an xdc file with rx and tx added to the constraint file.

cheers,

Jon

[ttrostel]

I found that after setting the UART to custom, run synthesis and then go look and a new netlist item will appear.  At that point you can assign the ports to pins with the standard tools and then do an implementation and bitstream.  I'm not certain how you got the ports to show on your block diagram.  I am not as familiar with the Vivaldo suite as I'd like to be yet ... very cool.

[jpeyron]

ttrostrel,

I deleted the connection that is automatically made to the uart usb. I then expanded the uart connections and set rx and tx to external.

cheers,

Jon

[pdm]

Hi All,

I too am working with my brand new Arty, and trying to connect an axi uart_lite to an external 3.3v 422 transceiver. Infact, I want to connect 4+ uartlites to trancievers, and control the transmission via a TCP packet. I'm tackling the single uart first and found this thread helpful in exposing the individual uart pins.

Being brand new to Vivado I cant seem to find out how to connect the uart rx and tx to physical pins. I want to use the shield pins for my custom 422 gang shield, and can see how you could drag an axi_gpio controller for shield pins 0-19 onto the schematic but that axi interface is obviously not what I want. Sorry if this process is trivial, but experimenting and searching google hasn't turned anything up for me.

Thanks

Paul

[jpeyron]

Hi pdm,

I used the arty xdc and changed the name of the pins i wanted to use to rx and tx and uncommented the lines used. I then right clicked on the design sourses and created a wrapper. I then made sure that the wrapper used the same names.

cheers,

Jon

Arty_Master.xdc

[pdm]

jpeyron,

Thanks for the pointers. I was able to get it built and verified output on my scope. 

I modified the .xdc you provided, added it to the project, and set it as the main constraint file and saved everything. I wasn't sure how to "create a wrapper" via the design sources menu. I right clicked on the diagram and added a "port" with the appropriate I/O direction and name. I assume that is effectively the same thing. I will try the menu method when I add more uarts.

Thanks,

Paul