I have the lpc3131 embedded artists board and I am working on a USB driver. I first converted the Keil example code to IAR code and got the USB working. I then tried to port it over to a different syntax and for some reason the following code does not reset the ep_QH (end point queue head) to make dQH (device queue head) values zero:
DQH_T* const ep_QH = (DQH_T*)DQH_BASE;
//memset fills the first n bytes of the memory area //pointed to by s with the constant byte c. //void *memset(void *s, int c, size_t n);
/* Zero out the Endpoint queue heads */ memset((void*)ep_QH, 0, EP_NUM_MAX * sizeof(DQH_T));
/* dQH Queue Head */ typedef volatile struct { Int32U cap; Int32U curr_dTD; Int32U next_dTD; Int32U total_bytes; Int32U buffer0; Int32U buffer1; Int32U buffer2; Int32U buffer3; Int32U buffer4; Int32U reserved; Int32U setup[2]; Int32U gap[4]; } DQH_T;
//Here's the memset function: #define _DLIB_STRING_SKIP_INLINE_MEMSET #pragma inline void * memset(void * _D, int _C, size_t _N) { __aeabi_memset(_D, _N, _C); return _D; }
It goes into the function and passes the correct parameters but it doesn't seem to change the value of dQH to zero. Anyone know why this is happening or a work around.
Just more thing - any reason for memset() of 16 bytes? Is that the only part of the *ep_QH entry you want cleared?
It will only clear the fields cap, curr_dTD, next_dTD and total_bytes. Not to many queues, lists etc would like some outsider to clear private fields. The next_dTD field might possibly chain the entries in the queue in which case a clear of it would break the queue.
Thank you so much for all the help. I realized the problem was that another programmer had commented out my SDRAM initialization function and so I was trying to read an address that was not memory mapped. My solution was to just change the address I was selecting to an internal onchip SRAM memory location instead.
Thanks again.