Question

Hello,

 

I am working UART receiver project .Project includes receive from PC and display on leds on fpga.But I am facing problem.whether i can be problem with ucf file or code.sceondly i am using PMOD connector.I am connecting ground and receiver pin to PMOD connector pin.anything else need to be connected pls help me .board i am using is basys2

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Hi @Gaurav_Mane, welcome to the forums!

I usually teach building a UART in stages

  1. Stage one: Blinky.  You've got to be able to turn on the LED's and turn them off at will.    You also need to be able to make them blink at a rate that you can "see" it.  These will help you debug your serial port.
  2. Stage two: make sure you have the pins right.  No matter how often I've built UART components, I consistently find schematics that label the serial port from the point of view of the "other" chip.  As the UART is set up, the lines are supposed to idle in the "high" (1'b1, or 3.3V) condition.  If you set up your blinky program so that the LED stays high for half a second following any time a UART wire goes low, you should be able to identify which wire is coming from the PC to your FPGA.  Don't forget to turn off hardware flow control in your terminal program. Make sure that by the time you are done you are sending the inputs into a two flip-flop synchronizer.
  3. Stage three: The wire that isn't coming from the PC should be going to the PC.

At this point you should know the wires and have them set properly in your UCF file.

The next step is harder, and involves getting your logic just right.  For this step, I would recommend getting your logic working with a UART simulator before trying to place it on your board.

For more details, feel free to check out this article.

Dan

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