use the uart port in nexys 4ddr board

[Javier olmos]

hello!! i want use the uart port, but when i send the data with the RS-232 interface its not appear in the virtual COM of my PC, i was try using the RTS and CTS pins but doesn´t work

[jpeyron]

Hi @Javier olmos,

Do you have the board files installed as shown in this tutorial? Are you using Microblaze and the uartlite ip core or using a pure HDL(Verilog/VHDL) project?  What version of Vivado are you using? What OS are you using on your PC? Here is the Nexys-4-DDR-GPIO VHDL project that sends data over the usb uart bridge.

thank you,

Jon

[Javier olmos]

Yes i have install they programs, I using HDL, i have the most recent version of vivado

 

[D@n]

@Javier olmos,

Welcome to the difficulty of getting your first design up and running!

Have you looked at or tried any of these techniques to figure out what's going wrong?

Have you tried running a known good design through the port?  Does your design pass simulation?

Dan

[Javier olmos]

this is the simulation, for now, only was using the transmisor for the experimentation. this design was test in the nexys 2 and its worked.

the value of Fbaud was modified for the simulation

[D@n]

So the design worked on your Nexys 2 board?  Does it still work through the same terminal on your Nexys-2 board?  Just to rule that out as a possibility.

One common problem with any new serial port is that the TX and RX lines are switched.  Digilent likes to mark them as TX or RX, but doesn't usually annotate on the schematic from whose perspective they are TX and RX.  For example, on my Nexys Video board, the XDC file labels the output of the serial port coming from the FPGA as "uart_rx_out".

An easy way to tell is to create a counter that controls an LED.  Examine one of the two ports, TX or RX.  Set the counter to start counting from zero any time the line is low.  Once the counter saturates, stop.  Now, as long as the counter hasn't saturated, set the LED.  This LED will now blink any time you send a character to your board--independent of having the right baud rate.  Only one of the two pins will respond properly.  (Make sure you have flow control "off" for this test)  The pin that properly responds is the RX input.

Next, create a simple design where you just connect the RX input to the output.  You should now be able to read (in double) from your board everything you type.  This will confirm that you have the proper wires selected for transmit and receive.

Dan

[Javier olmos]

yes, its worked in the nexys 2 board, but the difference is that the nexys 2 board has a  db-9 conector and the nexys 4 board has a UART port

[D@n]

@Javier olmos,

Sure!  That was why I was asking about pin mapping.  What pin are you using to output from your Nexys 4 board to your PC?
Dan

[Javier olmos]

Only four pines..look the picture.

[D@n]

@Javier olmos,

Hence, my recommendation would be that you work your way through your design, pin by pin, making sure you have the mapping right.  C4 is probably the easiest pin to test.  D4 is the next easiest.  Once you know you have these two pins working, then you can turn on flow control and check CTS and RTS.

While I'd love to offer a better recommendation than this, and to point you directly at the problem you are having, you haven't provided me with enough information (yet) to answer that question.

Dan

[Javier olmos]

Ok, would like more information but its is all that have. thank you by the atention and I'm sorry by my bad english.

[jpeyron]

Hi @Javier olmos,

Here is the resource center for the Nexys 4 DDR. Here is the master XDC. I would suggest to look at this demo as a reference on how to set up the xdc as well as the USB UART bridge. Are you using Verilog or VHDL? Can you attach your HDL code?

thank you,

Jon

[Javier olmos]

Hi! thank you by the atention. I could resolve the problem.its was in the pins designed in the user manual and in the sampling frequency ....thanks!!