7 Replies Latest reply on Apr 29, 2020 2:39 AM by VasanthR_91

    SIO vref configuration

    BrKo_3931586

      My config:

      I am using the 059 kit to program external highspeed SBI devices at 1.8V levels.  I don't want to cut tracks or remove VDDIO series resistor so I am trying to use the SIO pins to lower the Voh to 1.8V.  I am able to configure all of the P12 SIO pins using the Vref to 1.8V successfully and have working performance on all SIO pins except the I2C hardware dedicated pins P12[0],P12[1].  I get slow rising signals that go over the Vref level.  In the documentation there is a comment about configuring the output drive to 25mA sink to configure the pin as an SIO but I have found this made no difference.  I am correctly setting the drive level to Vref and I have a Vccd (1.8V SIO Only) reference in the design.

       

      My Issue:

      Are the I2Cx:SDA and I2Cx:SCL pins able to be reconfigured as standard SIO pins for other uses?

       

      Thanks

      Brian

        • 1. Re: SIO vref configuration
          VasanthR_91

          Hi Brian,

           

          The pins 12[0] and 12[1]  are hardware connected to the kitprog of the device.

          You can see the pull-ups given to these lines on the board. Could you please remove those resistors and measure again ?

           

          Best Regards,
          Vasanth

          • 2. Re: SIO vref configuration
            LePo_1062026

            Brian,

             

            Vasanth is correct about the source of the ~5V pull-ups.  I know you don't want to remove series resistors.

             

            Suggestion #2:

             

            Breakoff the KitProg board from the Target KIT-059.  This will eliminate the VDD pull-ups on P12.0 and P12.1.

             

            If you need to program the Target board later, you can connect the 5-pin interface between the KitProg (J7) and Target (J3).  NOTE: Breaking off the KitProg board:

            • disconnects the KitProg I2C functions to the Target.  (This solves your problem for this discussion).
            • disconnects the KitProg UART functions to the Target. (Loss of KitProg UART functions for debugging or control).  To regain use of the KitProg UART you can connect P12.6 and P12.7 between (J1 and J9).
            • disconnects KitProg supplied power to the Target.  (Requires you to provide power through the edge connector pins or through the onboard Target USB connector @ 5V.)

            Consult the CY8CKIT-059 schematic.

             

            Len

            • 3. Re: SIO vref configuration
              BrKo_3931586

              Vasanth and Len,

               

              Thanks for the feedback/help.  Yes you are correct and this does fix the 1.8V SIO.  I choose to remove the resistors, so that I can keep the original 059 functionality for programming and additional serial port.  I should know better than question the documentation because its been great so far. 

               

              An additional question, I have not used the programmer for any additional functions (GPIO,I2C) but I do use the programmer sometimes for the debugger and UART serial port.  I know I can download and debug the programmer code, however I don't see any need for the I2C lines on the programmer which is why I removed the resistors.  Since you guys understand all of the other potential applications, is these any need to the I2C lines except if you were going to combine them with target I2C lines.  That would tie the programmer and target on the same communications bus.  Might be useful, but my guess is the kit designer just decided to pass over the lines just for additional flexibility.  I have not worked with the bootloader either are these lines used for any thing that you can think of?

               

              Brian

               

              PS thanks again for the fast reply

              • 4. Re: SIO vref configuration
                BrKo_3931586

                I've had negative effects to removing the two pullup resistors on the 059 kit (R9,R7).  While they do fix my original problem of not being able to use the SIO ports (P12.0 and P12.1) in 1.8V ref volt supply, I now have serial port issues with the USBUART on the target device.  Before this modification I could program thru the programmer UART and use the USBUART for serial port control.  This worked nicely because I don't need to start and stop the terminal program when turning off or reprogramming (saves 10 seconds and lots of frustration when I forget).

                 

                Issue:

                Now the problem without R7 and R9 is my USBUART locks up all the time.  Strange how two lines that I thought were doing nothing is effecting my target USBUART?  Interesting enough the debugger UART appears to function properly. With the two pullup resistors removed the I2C inputs are now floating, however I do not have the I2C lines on the target configured (they are doing 1.8V SPI communications).  So is it possible the use of the 1.8V logic on the target that is still connected to the programmer PSOC and this somehow messes up the USBUART on the target?  My solution is to not use the programmer until I understand the issue. I'm going to load the kitprog code and see if I can understand what is causing the instability.

                • 5. Re: SIO vref configuration
                  BrKo_3931586

                  so much for that idea, the kitprog software isn't available so my best bet is to isolate the two I2C lines between the kitprog and target and see if this fixes the problem

                   

                  Brian

                  • 6. Re: SIO vref configuration
                    LePo_1062026

                    Brian,

                     

                    There are 4 other SIO lines on the Target board (P12.2, P12.3, P12.4 and P12.5).  Can you use two of them instead of P12.0 and P12.1 for I2C comm?

                     

                    Len

                    • 7. Re: SIO vref configuration
                      VasanthR_91

                      Hi Brian,

                       

                      Len's suggestion was better for re-using the board in other configurations. Unfortunately kitprom firmware is not available in public domain, only the hex file is available. Are you still facing issues with the USBUART lines ?

                       

                      Best Regards,
                      Vasanth