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Bulk transfer of Data via USB (Host side)

Hi everyone,

I am using a LM3S5951 controllers for one of my projects in which I need to implement a host side driver for Dot Matrix printer .

I am done with enumeration of the printer, but now I would like to know how can I send data to printers using bulk transfers. I am using the Stellaries USB Library for the same where I found some host side codes for keyboard and pendrive. I would like to know, how to go about this.

Regards

Dhanush

Parents

0 Chinzei Tsuneo over 11 years ago in reply to Dhanush Nair

> I have one IN endpoint for the printer.

The bulk IN endpoint of the printer interface is optional.
It’s role is specific to each printer model.
Unfortunately, Epson doesn’t open the information of the role (protocol) over the bulk IN.
You may get some printer status, or nothing.
Try it.

ulBytes = USBHCDPipeRead( g_USBHPRNDevice.ulBulkInPipe, pBuffer, sizeof(pBuffer) );

> I would also like to check whether the printer is busy or not like it has been checked using the 25 pin centronics using LPT.

NAK on the bulk OUT endpoint corresponds to the BUSY signal of Centronics.

While the endpoint is NAKing, USBHCDPipeWrite() (and USBHCDPipeRead()) blocks the caller thread. I believe this is the reason why you need "BUSY" signal.

Instead of these blocking calls, you may apply non-blocking USBHCDPipeSchedule() to start transfer over the bulk IN or OUT endpoint.

USBHCDPipeSchedule( g_USBHPRNDevice.ulBulkOutPipe, pBuffer, sizeof(pBuffer) );
or
USBHCDPipeSchedule( g_USBHPRNDevice.ulBulkInPipe, pBuffer, sizeof(pBuffer) );

When the transfer finishes, callback is called for each endpoint.
This callback is registered at USBHCDPipeAllocSize() in your USBHPRNOpen()

static void PRNEndpointCallback(uint32_t ui32Pipe, uint32_t ui32Event);

static void *
USBHPRNOpen(tUSBHostDevice *pDevice)
{
    ...
    ...
                g_sUSBHMSCDevice.ui32BulkInPipe =
                    USBHCDPipeAllocSize(0, USBHCD_PIPE_BULK_IN_DMA,
                                        psDevice,
                                        psEndpointDescriptor->wMaxPacketSize,
                                        PRNEndpointCallback);    // <-------
    ...
    ...
                g_sUSBHMSCDevice.ui32BulkOutPipe =
                    USBHCDPipeAllocSize(0, USBHCD_PIPE_BULK_OUT_DMA,
                                        psDevice,
                                        psEndpointDescriptor->wMaxPacketSize,
                                        PRNEndpointCallback);    // <-------

In the callback,

static void
PRNEndpointCallback(uint32_t ui32Pipe, uint32_t ui32Event)
{
  switch ( ui32Event ) {
    case USB_EVENT_TX_COMPLETE:   // transfer on OUT endpoint finishes
      //
      // notify to the main thread by a flag, or start another transfer
      //
      break;

    case USB_EVENT_RX_AVAILABLE:  // transfer on IN endpoint finishes
      // read out data into a buffer
      USBHCDPipeReadNonBlocking( g_USBHPRNDevice.ulBulkInPipe, pBuffer, sizeof(pBuffer) );
      break;
    default: break;
  }
}

Tsuneo

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