Hello Zen,
Please find the snippet below which contains the code for creation of DMA channel from U Port to P Port and from P Port to U Port.
This can be found in the file cyfxslfifoasync.c file. Here,
The dmaCfg.size gives the buffer size associated with the DMA channel. Note that size is same for both the channels here.
The dmaCfg.count gives the number of such buffers that are allocated to the DMA channel. This is also same for both the channels.
According to the code, currently the size of the DMA buffer is set based on the USB speed. That is it is 64 bytes for Full Speed, 512 for High Speed and 1024 for super speed. You can try varying the DMA buffer size. As you might be knowing that this example project makes use of default memory mapping for the 512 KB SRAM. That is, only 224 KB out of the available 512 KB SRAM of FX3 can be used for the creation of DMA Buffers. Out of this, some amount of memory is used for the creation of Control channel and UART debug channel. So, to be on the safe side, ensure that the total size of DMA buffers allocated is less than 218 KB. If this is not met, then the device will not enumerate. So when you are increasing the DMA Buffer size, if the total size of allocated DMA buffers for both the channels go beyond 218 KB, please reduce the number of buffers or the size of DMA buffer.
Best Regards,
Jayakrishna
