6748 USB 32Bit FIFO and 8 BIT DATA

Mark Bends

I am having trouble enumerating a USB device on the USB0 channel of a 6748. I receive and correctly decode the GET_DESCRIPTOR packet. My response is not recognized by the host.

I believe the problem is in writing to the TXFIFO0. In order to use the RX fifo, I had to read the data 32bits at a time (I tried declaring the RXFIFO as a char, to no effect). I assume the data written to the TXFIFO must be written as a 32bit value. What happens in the case with 18 bytes of data? I can find no register the allows me to set the TX data length in bytes.

This is my intended descriptor:

const USB_DEVICE_DESCRIPTOR DeviceDescriptor = {
    sizeof(USB_DEVICE_DESCRIPTOR), /* bLength */
    TYPE_DEVICE_DESCRIPTOR,        /* bDescriptorType */
    0x0020,                        /* bcdUSB USB Version 1.1 */
    2,                             /* bDeviceClass */
    0,                             /* bDeviceSubclass */
    0,                             /* bDeviceProtocol */
    64,                             /* bMaxPacketSize 64 Bytes */
    0x045E,                        /* Test Board */
    0x930A,
    0x0000,                        /* bcdDevice */
    1,                             /* iManufacturer String Index */
    0,                             /* iProduct String Index */
    0,                             /* iSerialNumber String Index */
    1                              /* bNumberConfigurations */
};

This is the trace data that is written to the FIFO:

78 Write Endpoint 0 Bytes-18

79 EP0-00200112

80 EP0-40000002

81 EP0-930A045E

82 EP0-00010000

83 EP0-11800100

Thanks for the help.

over 15 years ago

0 Mark Bends over 15 years ago

Prodigy 250 points

The following code, while ugly, does write to the tx buffer correctly:

void usb_WriteEndpoint(unsigned char Endpoint, const uint8_t *Buffer, unsigned char Bytes)
{
#define FIFO0_Offset 0x420
uint8_t i;
// uint8_t w = 0;
uint8_t * fifo_addr = (uint8_t *)USB_OTG;

fifo_addr += (FIFO0_Offset + (Endpoint * 4));

   LOG_printf(&trace, "Write Endpoint %i Bytes-%i",Endpoint, Bytes);
USB_OTG->INDEX = Endpoint;
if (Bytes > 0)
{
  for (i = 0; i < Bytes; i++){
   *(fifo_addr + (i % 4)) = Buffer[i];
        LOG_printf(&trace, "EP0-%.2X (%X) ", Buffer[i], fifo_addr + (i%4));
  }
}
USB_OTG->CSR |= (USB_TXPKTRDY);
}

Remove the LOG_printf() if not using DSP BIOS

Processors

Processors forum

6748 USB 32Bit FIFO and 8 BIT DATA