2 Replies Latest reply on Jan 16, 2010 1:20 AM by john.gulbrandsen

    PSoC 3 Cut-through USB/DMA mode example?

    john.gulbrandsen
              I need to use the cut-through USB/DMA mode in my design. Is there any example or more detailed appnote available?   
         
      Background: I want to use two 512 byte ISO endpoints. The maximum endpoint buffer in the PsoC 3 is in total 512 byte so i can only use a 256 byte endpoint buffer per endpoint. By using cut-through USB mode, the PSoC 3 will only keep part of the endpoint data in the endpoint buffer such that up to 1023 byte endpoint buffers can be simulated. As data is being sent to the host, more data is being DMAed from RAM to the endpoint buffer. Very nice but very little documentation available.   
        • 1. Re: PSoC 3 Cut-through USB/DMA mode example?
          content.librarian
                  There are a few app notes on using USB, and one app note on DMA (AN52705), but I am unaware of one that covers exactly what you are looking for. The DMA app note was just recently released (1/13).   
             
          Have you reviewed any of the existing DMA & USB app notes?   
             
          -Bobby   
          • 2. Re: PSoC 3 Cut-through USB/DMA mode example?
            john.gulbrandsen
                    Yes, I have combed through all app notes but nothing covers cut-through USB mode. It is clear that the firmware needs to setup the DMAC to "prime" the endpoint with data and that the DMAC needs to send more data to the USB block as data is being sent to the host (USB IN EP). It is, however, completely undocumented HOW to configure the TDs to work with cut-through mode.   
               
            I am trying to figure this out the hard way but i would very much appreciate if an example could be produced that would cut down on the guesswork.   
               
            Thanks.