Hi, I have written a driver for Cypress EZ USB FX based device. To test ISO Writes, I have written a firmware where in, in the SOF ISR, I am copying the contents of OUT8DATA to IN8DATA. (in my firmware, I have created two ISO pipes - one IN and one OUT and I am trying to loopback all the data written to the OUT pipe onto the IN pipe. The Problem I am facing is I never get the exact data back which I had written to the ISO OUT pipe. I have initialized the registers properly and my Sof()looks like this Sof() { for (i=0; i<62; i++) { IN8DATA = OUT8DATA; } EZUSB_IRQ_CLEAR(); USBIRQ = bmSof; } could anyone suggest me how can I achieve the desired thing ... Thanks Rahul Gupta