UsbStartIsoTransfer

Description
Starts asynchronous Isochronous Transfers with a specific endpoint.

Syntax
ulrc = UsbStartIsoTransfer(Handle,ucEndpoint,ucAltSetting,ulEvent,pucParm,pucData,usFrameLength,usFrameCount)

Parameters

 * Handle : the Device Handle received from the previous UsbOpen.


 * ucEndpoint : the Endpoint Number appropriate for the data transfer.


 * ucAltSetting : the Alternate Setting of the interface having this endpoint.


 * ulEvent : the handle of the event semaphore to be posted on completion.


 * usFrameLength : the maximum number of bytes in an isochronous frame.


 * usFrameCount : the number of isochronous frames in the Data Buffer.


 * pucParm : the address of the Parm Buffer with usDatalength and usStatus.


 * usDataLength : the variable to specify/receive the number of data bytes.


 * usStatus : the variable to receive the asynchronous Completion Status.

For device-to-host data transfer:


 * pucData : the address of the Data Buffer to receive the bytes transferred.

For host-to-device data transfer:


 * pucData : the address of the Data Buffer with the bytes to be transferred.

Return Code
0x0000 - NO_ERROR

Errors
0x0057 - ERROR_INVALID_PARAMETER 0x1B58 - USB_NOT_INIT 0xFF0D - ERROR_INVALID_DATA 0xFF13 - ERROR_I24_INVALID_PARAMETER 0xFF13 - USB_IDC_PARMERR 0xFF18 - USB_IDC_ADDRINV 0xFF37 - ERROR_DEV_NOT_EXIST 0xFF5D - EROR_NO_ITEMS 0xFFA7 - ERROR_LOCK_FAILED

Status Code
0x0000 - USB_IORB_DONE

Errors
0x4000 - USB_IORB_REQUEST 0x80XX - USB_IORB_FAILED

Remarks
Concatenated Payloads are being used when usFrameCount equals zero. When UsbStartIsoTransfer is issued and Concatenated Payloads are being used then usDatalength in the Parm Buffer must be set to the number of bytes to be transferred. When the transfer request has been completed then usDataLength in the Parm Buffer contains the number of bytes transferred.

Individual Iso Frames are being used when usFrameCount is larger than zero. When UsbStartIsoTransfer is issued and Individual Iso Frames are being used then each element of the additional usFrameSize[FrameCount] array in the Parm Buffer must be set to usFrameLength. When the transfer request has been completed then each element of the additional usFrameSize[FrameCount] array contains the number of bytes transferred. Individual Iso Frames are stored in the usFrameData[FrameCount][FrameLength] array in the Data Buffer.

Example Code
//Code Snippet - UsbStartIsoTransfer // Individual Iso Frames { APIRET ulrc; PUCHAR pucData; UCHAR ucAltSetting = 1; UCHAR ucData[FrameCount][FrameLength]; UCHAR ucEndpoint = 0x86; ULONG ulTimeout = 8000; USHORT usFrameLength = FrameLength; USHORT usFrameCount = FrameCount;
 * 1) define FrameCount 60
 * 2) define FrameLength 0x44

HEV hIsoComplete; PHEV phIsoComplete; typedef struct { USHORT usStatus; USHORT usDataLength; USHORT usFrameSize[FrameCount]; } USBCALLS_ISO_RSP, *PUSBCALLS_ISO_RSP; PUSBCALLS_ISO_RSP pIsoResponse; USBCALLS_ISO_RSP IsoResponse; int i;

//acquire semaphore phIsoComplete = &hIsoComplete; ulrc = DosCreateEventSem(NULL,phIsoComplete,DC_SEM_SHARED,FALSE); printf("\nDosCreateEventSem - ulrc: 0x%04X (%hu)",ulrc,ulrc);

//start isochronous data transfer IsoResponse.usDataLength = sizeof(ucData); pIsoResponse = &IsoResponse; pucData = &ucData[0][0]; for (i=0;i<usFrameCount;i++) IsoResponse.usFrameSize[i] = usFrameLength; ulrc = UsbStartIsoTransfer(Handle,ucEndpoint,ucAltSetting,hIsoComplete,(PUCHAR)pIsoResponse,pucData,usFrameLength,usFrameCount); printf("\nUsbStartIsoTransfer - ulrc: 0x%04X (%hu)",ulrc,ulrc);

//await isochronous data transfer complete ulrc = DosWaitEventSem(hIsoComplete,ulTimeout); printf("\nDosWaitEventSem - ulrc: 0x%04X (%hu)",ulrc,ulrc); if (!ulrc) //success {   ulrc = IsoResponse.usStatus; printf("\nCompletion Status - ulrc: 0x%04X (%hu)",ulrc,ulrc); if (!ulrc) //success {     int j; printf(" - isochronous data:"); for (j=0;j<usFrameCount;j++) {       if (IsoResponse.usFrameSize[j]) printf("\n"); for (i=0;i<IsoResponse.usFrameSize[j];i++) {         printf("%02X",ucData[j][i]); }     }    }  }  else {   // failure awaiting isochronous data transfer completion UsbCancelTransfer(Handle,ucEndpoint,ucAltSetting,hIsoComplete); }

//release semaphore ulrc = DosCloseEventSem(hIsoComplete); printf("\nDosCloseEventSem - ulrc: 0x%04X (%hu)",ulrc,ulrc); }

Related Functions

 * UsbCancelTransfer
 * UsbIsoOpen
 * UsbOpen