5 Replies Latest reply on Nov 7, 2014 4:57 AM by pavankumar.vibhute

    Passthrough

    alun.evans

       I have a design where I have a SPI Master proxying for several SPI Slaves which is working well.

         

      I was wondering about being able to directly connect one of the Slaves' pins to the Master's pins, so that the PSoC isn't involved as all, i.e.:

         

      Slave---[SPI_M, SPI_S0]---Master_0

         

      to =>

         

      Slave---[~~~]---Master_0

         
          Any thoughts on this? I can just directly connect the pins, but I wonder if I need to change their properties?   
         
              
         
              
         
          thanks,   
         
              
         
              
         
          A.   
        • 1. Re: Passthrough
          ki.leung

          That depends on the purpose of the orginal design. 

             

          You need to check if there is any conversion(I.E. chage of content by the PSOC) being done. 

          • 2. Re: Passthrough
            alun.evans

            The PSoC is only doing "magic" to enable the 1:N connection, the two devices communicate fine in a 1:1 configuration (with direct connection.

               

             

               

            A. 

            • 3. Re: Passthrough
              ki.leung

              If the SPI master can access multiple slaves (controlling the CS lines to the slaves itself), then you do not need the PSOC      

               

                 

              If you only use one slave and talk to one slave, you don’t need the PSOC.      

               

                 

              If you need PSOC to talk to multiple slaves and the master cannot control the CS lines, then there must be communication between the PSOC and the master to know which CS line to assert. If this true, directly connection the master to the slave means all messages to the “SLAVES” would go to that slave that is now directly connected to the master.      

               

              • 4. Re: Passthrough
                alun.evans

                I realize that I have not written my statement very clearly:

                   

                I have a design where I have a single SPI Slave device connected to a PSoC SPI Master, which proxies for several PSoC SPI Slaves connected to several SPI Master devices.

                   

                 

                   

                One PSoC, one SPIS Device, multiple SPIM Devices.

                   

                 

                   

                I had been thinking of putting in sets of multiplexers to directly connect the phsyical SPI Slave device through to the zero-th SPI Master physical device, thus bypassing the PSoC's SPI Master and SPI Slave(s).

                • 5. Re: Passthrough
                  pavankumar.vibhute

                   I didn't understand completely your requirement. If you can put block diagram then it is helpful (now that you can paste pictures in forum posts). 

                     

                  Also, note that there are digital mulitplexers in PSoC. You can use those to multiplex lines between multiple SPI devices.