Nios behaving erratically?

Thanks BadOmen.

You are correct about the volatile functionality. My recollection was wrong as I hadn&#39;t looked at that topic in over a year. I guess my memory is going http://forum.niosforum.com/work2/style_emoticons/<#EMO_DIR#>/laugh.gif

As I said, the closest I&#39;ve gotten to "working" software has been with the non-cached processor. I&#39;m presently trying to cut out code to test a non-optimized version of code.

Your loop looks very similar to what I&#39;m doing. My proof of concept involved a Cypress-based USB interface for our product. I got as far as doing a simple loopback test and stalled out there due to my mysterious printf/variable problem. Below is the simple section of code. It reads until the USB chip&#39;s status shows empty. IIRC (long time since working on this problem), removing the no_activity assignment or incrementing through the data array rather than using only data[0] would break the loopback. Furthermore, I believe that if I separated the loop into two loops (read and write) using the variable j to keep track of the number points read and making that the terminal count for the writeback, the code would no longer work unless I put a printf statement in there somewhere. I could never get the two loops running. My hope was to eventually get a DMA transfer running so I could test throughput.

Sorry for my vague recollections. Like I said, I abandoned the USB interface feature to finish other system features upon which I encountered the FIFO/state machine problem.

Here&#39;s my loop:

void USB_data_loopback(void)

{

volatile alt_u8 i,j;

alt_u16 data[128];

alt_u16 len;

no_activity = 1;// clear flag

if (got_out_data) //The FLAGS int tells us we have out data

{

got_out_data = 0;

if (IORD_ALTERA_AVALON_PIO_DATA(USB_STATUS_PIO_BASE)&0x02)

{

j = 0;

while(IORD_ALTERA_AVALON_PIO_DATA(USB_STATUS_PIO_BASE)&0x02)

{

data[0] = IORD(USB_SX2_BASE, 0x00);

// j++;

IOWR(USB_SX2_BASE, 0x02,(alt_u16)data[0]);

}

.

.

.

I am resuming my quest for a functional USB interface today. While it is not essential for our product, I need to understand this behavior as it may reappear in the essential code. I have learned a lot about the Nios tools over the past year and plan to use them, including the debugger and breakpoints. Hopefully i will find more clues.

thanks.

steve