Texas Instruments TMS320DM357 manual While usbRegs-PERITXCSR

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Example 4. Programming the USB DMA Controller (continued)

usbRegs->CHANNEL[i].RCPPIDMASTATEW6 = 0; tx_desc[i] = 0;

rx_desc[i] = 0;

}

//Routine to flush TX fifo.

//Must call this routine twice for double-buffered FIFO void flush_tx_fifo(int ep) {

int index_save;

int status;

index_save = usbRegs->INDEX;	// Save the index to restore later
usbRegs->INDEX = ep;	// Set the index to the desired endpoint
status = usbRegs->PERI_TXCSR & 3;	// Isolate the TxPktRdy and FIFONotEmpty bits
if (!(status)) {	// Nothing showing in FIFO
usbRegs->PERI_TXCSR = 1;	// Set TxPktRdy in case there is a partial
packet already in FIFO
}
usbRegs->PERI_TXCSR = ((usbRegs->PERI_TXCSR & 0xFFFC) 8);		// Write TXCSR with flush
bit set, FIFONotEmpty=0, and TxPktRdy=0.
while (usbRegs->PERI_TXCSR & 8);	// Keep looping until the flush bit clears
usbRegs->INDEX = index_save;	// Restore the index to previous value
}

//Routine to start the TX DMA for a given channel void start_tx_dma(int ch) {

//Must have at least one descriptor before turning on TX DMA if (rx_desc[ch] < 1) {error++;} else {

//Flush FIFO (2 times in case it is double-buffered) flush_tx_fifo(ch+1);

flush_tx_fifo(ch+1);

// Start the DMA

usbRegs->TCPPICR = 1; //Enable Tx CPPI DMA usbRegs->CHANNEL[ch].TCPPIDMASTATEW0 = (Uint32)(&tx_bufferDesc[ch][0]);

CSL_FINS(usbRegs->PERI_TXCSR,USB_PERI_TXCSR_DMAEN,1);	// TXCSR, bit DMAReqEnab
}
}

// Routine to add a TX descriptor

void add_tx_descriptor(int ch, unsigned char * inBuf, int bytes) { if ((bytes < 0) (bytes >65535)) {bytes = 64; error++;}

//Link previous buffer to this one if this is not the first descriptor of the channel if (tx_desc[ch] > 0) tx_bufferDesc[ch][4*(tx_desc[ch]-1)] =

(Uint32)(&tx_bufferDesc[ch][4*tx_desc[ch]]);

// Set up DMA buffer descriptors
tx_bufferDesc[ch][4*tx_desc[ch]+0] = (Uint32)(0x00000000);		// Next Descriptor pointer
tx_bufferDesc[ch][4*tx_desc[ch]+1] = (Uint32)inBuf;		// Buffer pointer
tx_bufferDesc[ch][4*tx_desc[ch]+2] = (0x0000 << 16) bytes;		// [31:16] Buffer offset
[15:0] Buffer length
if (bytes == 0) bytes = ZERO_BYTE 1;	// Set the ZERO_BYTE bit and size 1 byte
tx_bufferDesc[ch][4*tx_desc[ch]+3] = SOP EOP OWNER bytes;		// [31]=SOP, [30]=EOP,
[29]=owner, [28]=EOQ, [23]=zero-byte, [19]	= rxabort, [15:0]=packet length

//If DMA already enabled and has stopped, write this to the TX Queue head pointer if ((usbRegs->TCPPICR == 1) && (usbRegs->CHANNEL[ch].TCPPIDMASTATEW0 == 0))

usbRegs->CHANNEL[ch].TCPPIDMASTATEW0 = (Uint32)(&tx_bufferDesc[ch][4*tx_desc[ch]+0]);

SPRUGH3–November 2008 Universal Serial Bus (USB) Controller 21

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