Posted on May 17, 2011 at 14:28How many bytes do you send with single USB_SIL_Write() call?
Above code supposes up to 64 bytes for single call.
To send just 64 bytes, the second USB_TX() call is required to terminate the transfer with ZLP (Zero-Length Packet)
USB_TX( buffer, 64 ); // send 64 bytes transaction
USB_TX( NULL, 0 ); // send ZLP
To send more than 64 bytes, the transfer is split into transactions.
For example of 100 bytes,
USB_TX( buffer, 64 ); // send the first 64 bytes
USB_TX( buffer + 64, 36 ); // send the next 36 bytes
But if you need to call multiple USB_TX() contiguously to send large data, like above examples, the endpoint interrupt (callback) gives better implementation.
//
// send greater than 64 bytes, too
//
#define CDC_BULK_IN_EP_SIZE 64
typedef struct {
struct {
unsigned occupied : 1;
unsigned send_ZLP : 1;
};
u8 * buffer;
int length;
} t_CDC_bulk_IN;
volatile t_CDC_bulk_IN cdc_bulk_IN;
void CDC_Block_TX(u8 * sendData, int length)
{
int len;
while (cdc_bulk_IN.occupied); // wait until the last transaction finishes
// now, the endpoint is available for this routine
// send ZLP, when the transfer size is
// just the multiple of the wMaxPacketSize of the EP
cdc_bulk_IN.send_ZLP = ((length & (CDC_BULK_IN_EP_SIZE - 1)) == 0);
// calculate the first transaction size
len = (length < CDC_BULK_IN_EP_SIZE) ? length : CDC_BULK_IN_EP_SIZE;
cdc_bulk_IN.buffer = sendData + len; // for the next transaction
cdc_bulk_IN.length = length - len;
cdc_bulk_IN.occupied = TRUE;
// send the first transaction
USB_SIL_Write(EP1_IN, sendData, len); // copy data to the endpoint buffer
SetEPTxValid(ENDP1); // make the endpoint ready for transaction
}
usb_conf.h
/* CTR service routines */
/* associated to defined endpoints */
// #define EP1_IN_Callback NOP_Process // <------ comment this line
usb_endpoint.c
// send the second and later transactions
void EP1_IN_Callback( void )
{
int len;
if (! cdc_bulk_IN.occupied) return;
// calculate the next transaction size
len = (cdc_bulk_IN.length < CDC_BULK_IN_EP_SIZE) ? cdc_bulk_IN.length : CDC_BULK_IN_EP_SIZE;
if ( (len != 0) || cdc_bulk_IN.send_ZLP) {
USB_SIL_Write(EP1_IN, cdc_bulk_IN.buffer, len); // copy data to the endpoint buffer
SetEPTxValid(ENDP1); // make the endpoint ready for transaction
} else {
cdc_bulk_IN.occupied = FALSE; // finish transfer
return;
}
// for the next transaction
if ( len == 0 ) {
cdc_bulk_IN.send_ZLP = FALSE;
}
cdc_bulk_IN.buffer += len;
cdc_bulk_IN.length -= len;
}
usb_prop.c
void Virtual_Com_Port_SetConfiguration(void)
{
DEVICE_INFO *pInfo = &Device_Info;
if (pInfo->Current_Configuration != 0)
{
/* Device configured */
bDeviceState = CONFIGURED;
cdc_bulk_IN.occupied = FALSE; // initialize variables for USB communication
}
}
Tsuneo
