Cypress EX-USB FX3, Руководство программиста

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94 FX3 Programmers Manual, Doc. # 001-64707 Rev. *C
FX3 Application Structure
}
8.1.2.6 USB Event Callback
The USB events of interest are: Set Configuration, Reset and Disconnect. The slave FIFO loop is
started on receiving a SETCONF event and is stopped on a USB reset or USB disconnect.
/* This is the callback function to handle the USB events. */
void
CyFxSlFifoApplnUSBEventCB (
CyU3PUsbEventType_t evtype,
uint16_t evdata
)
{
switch (evtype)
{
case CY_U3P_USB_EVENT_SETCONF:
/* Stop the application before re-starting. */
if (glIsApplnActive)
{
CyFxSlFifoApplnStop ();
}
/* Start the loop back function. */
CyFxSlFifoApplnStart ();
break;
case CY_U3P_USB_EVENT_RESET:
case CY_U3P_USB_EVENT_DISCONNECT:
/* Stop the loop back function. */
if (glIsApplnActive)
{
CyFxSlFifoApplnStop ();
}
break;
default:
break;
}
}
8.1.2.7 DMA Setup
■
The Slave FIFO application uses 2 DMA Manual channels. These channels are setup once a Set
Configuration is received from the USB host. The DMA buffer size is fixed based on the USB
connection speed.
/* Create a DMA MANUAL channel for U2P transfer.
* DMA size is set based on the USB speed. */
dmaCfg.size = size;
dmaCfg.count = CY_FX_SLFIFO_DMA_BUF_COUNT;
dmaCfg.prodSckId = CY_FX_PRODUCER_USB_SOCKET;
dmaCfg.consSckId = CY_FX_CONSUMER_PPORT_SOCKET;
dmaCfg.dmaMode = CY_U3P_DMA_MODE_BYTE;