10 Replies Latest reply on Aug 13, 2019 8:26 PM by bhfletcher

    HD_GPIO voltage issue

    aeiforos

      dear all,

      I'm a newcomer to ultra96's world and I'm facing some issues. My purpose is to connect a led to a HD_GPIO_1 (LS_Header) and turn it on/off. To do that will be used a led I own (not a board's led, PS led) and a breadboard.

      Vivado Implemented design--I/O ports:

      direction=out

      Package Pin=F8

      Bank=26

      I/O Std=LVCMOS25

      VCCO=2.5

      Drive Strength=8(mA)

      PullType=None

      Off chip termination=None

       

      Downloading and running the application I wrote at SDK, led really turns on/off. When I measure the voltage (by a digital multimeter) at pin 5 (HD_GPIO_1 mapped to pin 5 at ultra96 V2) I found it 1.82 Volts. Is that possible? Why voltage isn't 2.5Volts as stated before?

      Even when setup I/O std to LVCMOS33, voltage is still 1.82Volts. Does I/O std and VCCO affects Voltage at all?

       

      Thank you in advance

      Christos

        • Re: HD_GPIO voltage issue
          michaelkellett

          Check (on the schematic) what voltage is actually connected to the chip to power bank 26.

          Telling the design tools that the bank is powered with 2.5V won't affect what it is physically connected to.

           

          MK

          1 of 1 people found this helpful
            • Re: HD_GPIO voltage issue
              jafoste4

              Hi,

               

              Please look into what MK is referring too. Bank 26 is powered with 1.8V.

               

              -Josh

              3 of 3 people found this helpful
              • Re: HD_GPIO voltage issue
                aeiforos

                Dear Joshua thank you for your reply
                What is "MK" that you refered ? I apologize, as a newbie I don't understand many acronyms yet...

                Talking about Bank 26 where did you find that HD_GPIO voltage is 1.8Volts ? I read Ultra96-V2 Hardware User's Guide many times but there is not a clear reference for me. Also I can confirm that HD_GPIO voltage is 1.8Volts because I have measured that by a digital multimeter.

                 

                Best Regards
                Christos

                • Re: HD_GPIO voltage issue
                  aeiforos

                  Dear Michael Hi!

                  I checked Ultra96-V2 Rev1 Schematic. pdf and I found that (please refer to the attached screenshots):

                  I can confirm that voltages on pins 1, 2, 35, 36, 37, 38, 39, 40 are as those at the refered screenshot, because I have measured them. But which one voltage (VCC_PSAUX=1.8V,  VSYS_IN=+12V, +5Volts)  is actually connected to the chip to power bank 26 ? Did I missed something ?

                  At Ultra96-V2 Hardware User's Guide, on page10 said:

                  "Zynq UltraScale+ MPSoc Programmable Logic (PL) provides two types of I/O banks: High density (HD) banks and high performance (HP) banks. HD banks support a limited number of single-ended I/O standards with speeds up to 250Mbps and VCCO voltages up to 3.3V.
                  HP banks support a large variety of high-speed I/O standards, including differantial I/O and support VCCO voltages up to 1.8V"
                  So the user's guide refers that HD banks (as Bank 26 is) support voltages up to 3.3Volts, am I doing right ?

                   

                  Best Regards
                  Christos

                  1 of 1 people found this helpful
                    • Re: HD_GPIO voltage issue
                      jafoste4

                      Hi Christos,


                      The reference your referring to in the HW User Guide is the available voltage levels for that individual MPSOC bank. Its a generic statement saying that the HD bank can support up to 3.3V. In the Ultra96-V2 case we set this voltage to 1.8V. However if you did your own PCB hardware design you could choose to set this voltage up to 3.3V.

                       

                      Also in my above statement I showed how BANK 26 is supplied its voltage.

                       

                      -Josh

                      2 of 2 people found this helpful
                  • Re: HD_GPIO voltage issue
                    dougw

                    Is the LED connected directly from your I/O pin to ground?

                    If so it really needs a resistor in series, otherwise the voltage cannot go above the LED (diode) voltage.

                    1 of 1 people found this helpful