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External PMOD pin Grounding

Former Member

Hi All

I am trying to connect up a ADC to the PMOD connections on the ZedBoard but am having trouble with the output pins connections. Through an oscilloscope the pins don't look like they are being driven properly. An output pin takes about 2 seconds to reach 3.3V once toggled.

My XDC file is as follows for each pin.

set_property PACKAGE_PIN "W12" [get_ports "TRIG"]
set_property IOSTANDARD "LVCMOS33" [get_ports "TRIG"]
set_property PIO_DIRECTION "OUTPUT" [get_ports "TRIG"]
set_property slew "fast" [get_ports "TRIG"]
set_property drive "8" [get_ports "TRIG"]

...

If anyone has any suggestions or a list of steps to interface to these pins please let me know.

  • 0

    Hello Alex,

     

    I set up a simple Zedboard design in Vivado 2013.3 with an AXI_GPIO output to the PMOD pin JB1 (W12), first with the simple XDC constraints:

     

    set_property package_pin w12 [get_ports TRIG]

    set_property iostandard lvcmos33 [get_ports TRIG]

     

    Then wrote a simple program in SDK to drive the signal high and low using Xil_Out32. It seems to toggle high and low just fine, with sharp edges and at a rate of ~ 200 nsec. per level change. I added in your other XDC constraints with the same results. I am monitoring the JB1 pin with no load and it is swinging from 0v to 3.3v.

     

    Are you seeing a slow rise time that might indicate the load is more than the 8 mA can drive or an actual 2 sec. delay with a sharp rising edge?

     

    -Gary