Universal Serial Bus Controller User's Guide

1.6 Industry Standard(s) Compliance Statement
Introduction www.ti.com
Example 4. Programming the USB DMA Controller (continued)
// Increment descriptor counter
tx_desc[ch]++;
}
// Routine to start the RX DMA for a given channel
void start_rx_dma(int ch) {
int index_save;
index_save = usbRegs->INDEX; // Save the index to restore later
// Must have at least 3 descriptors to receive anything
if (rx_desc[ch] < 2) {error++;} else {
usbRegs->INDEX = ch+1;
usbRegs->RCPPICR = 1; //Enable Rx CPPI DMA
usbRegs->CHANNEL[ch].RCPPIDMASTATEW1 = (Uint32)( & rx_bufferDesc[ch][0]);
CSL_FINS(usbRegs->PERI_RXCSR,USB_PERI_RXCSR_DMAEN,1);
// Update the buffer count register. This ADDS to the existing value, does not
overwrite.
switch (ch) {
case 0: usbRegs->RBUFCNT0 = rx_desc[ch]; break;
case 1: usbRegs->RBUFCNT1 = rx_desc[ch]; break;
case 2: usbRegs->RBUFCNT2 = rx_desc[ch]; break;
case 3: usbRegs->RBUFCNT3 = rx_desc[ch]; break;
}
}
usbRegs->INDEX = index_save; // Restore the index to previous value
}
//Function to build Rx DMA descriptors
void add_rx_descriptor(int ch, unsigned char * outBuf, int bytes) {
int index_save;
index_save = usbRegs->INDEX; // Save the index to restore later
if (bytes < 1) {bytes = 64; error++;}
usbRegs->INDEX = ch+1;
// Link previous buffer to this one if this is not the first descriptor of the channel
if (rx_desc[ch] > 0) rx_bufferDesc[ch][4*(rx_desc[ch]-1)] =
(Uint32)( & rx_bufferDesc[ch][4*rx_desc[ch]]);
rx_bufferDesc[ch][4*rx_desc[ch]+0] = (Uint32)(0x00000000); // Next descriptor
rx_bufferDesc[ch][4*rx_desc[ch]+1] = (Uint32)outBuf; // Buffer address
rx_bufferDesc[ch][4*rx_desc[ch]+2] = (0x0000 < < 16) | bytes; // Rx buffer size in bytes
rx_bufferDesc[ch][4*rx_desc[ch]+3] = OWNER | 0; // OWNER
rx_desc[ch]++;
usbRegs->INDEX = index_save; // Restore the index to previous value
}
This device conforms to USB 2.0 Specification and On-The-Go Supplement to the USB 2.0 Specification
Rev 1.0a.
22 Universal Serial Bus (USB) Controller SPRUGH3 – November 2008
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