Abstract: A system and method for transferring data over an external transmission medium. A host computer is coupled to a device through a serial bus. A transfer object is configurable to encapsulate data transfer-related functionality, providing a generic interface for transmission of data over a variety of external transmission media and protocols. A user makes one or more transfer requests. Transfer objects corresponding to each request are built and linked together to form a sequential chain. The requests of the transfer objects are executed sequentially. If the current transfer object is the first in the chain, the request is executed on a current thread at passive level or higher, otherwise the request is executed on a system (kernel) thread at dispatch level. When a response to the request returns, control is returned to the current transfer object. The process is repeated until all transfer objects are processed.

Abstract: A system and method for transferring data over a communications medium using data transfer links. A host computer may couple to a device through a serial bus. A buffer of contiguous virtual memory addresses may correspond to non-contiguous physical addresses, which may be stored in a linked list of transfer nodes, preserving the order of the original virtual buffer elements. Each transfer node specifies a data transfer between the host and device, and may be executed by the device DMA Controller. Each node may contain source and/or destination address information, size of the data to be transferred, and a link to the next node. The transfer nodes may be transferred to the device using a double-buffering scheme wherein the device executes the nodes from one half of the link buffer while the host computer transfers further nodes to be executed to the other half of the link buffer. The buffer halves may be switched back and forth between these two processes until all links are executed.

Abstract: A system and method for transferring data over a communications medium. A host is coupled to a device through a serial bus lacking error handling capabilities, such as an IEEE 1394 bus. The host may control the device by sending requests accessing its memory registers. The host generates a first request to the device to access a memory address location of the device, and which includes an address and status information indicating whether a prior request to the memory address location returned successfully. The device examines the status information to determine if it is a retry of a prior request, and if so, determines if the prior request completed successfully to the memory address location by comparing the address and data transfer size of the first request to those of the prior request. If identical, then the prior request completed successfully to the memory address location, and the request is ignored. Otherwise, the device retries the prior request.

Abstract: A USB-based data acquisition system including virtual DMA software which increases USB data transfer rates with minimal changes to DAQ driver level software. The virtual DMA software operates to receive or intercept DMA instructions provided by the DAQ driver level software to program a DMA controller to acquire data from the device. The virtual DMA software intercepts the DMA instructions and emulates operation of the DMA controller in software. The virtual DMA software operates to request the data in bulk packets from the device. The virtual DMA software then stores the received packets of data in the addresses specified in the DMA instructions. The virtual DMA software thus emulates operation of a DMA device, thus “fooling” the DAQ driver level software into thinking the data is being acquired using real DMA transfers. Thus, the present invention allows for much faster data transfers, while requiring minimal or no changes to the existing DAQ driver level software.