CDA CD 60 Especificaciones descargar pdf (Pagina 13)

PCI CD and PCI CDa

Document Number: 008-00965-06 EDT Public Revision: I December 2004

Template: edt.dot

Page 13

EdtDev *edt_p = edt_open_channel("pcd", 1, 2) ;

char buf[1024] ;

int numbytes, outfd = open("outfile", 1) ;

* Because read()s are noncontinuous, unless is there hardware

* handshaking there will be gaps in the data between each read().

while ((numbytes = edt_read(edt_p, buf, 1024)) > 0)

write(outfd, buf, numbytes) ;

edt_close(edt_p) ;

}

You can use ring buffer mode for real-time data capture using a small number of buffers (usually four

of 1 MB) configured in a round-robin data FIFO. During capture, the application must be able to

transfer or process the data before data acquisition wraps around and overwrites the buffer currently

being processed.

The example below shows real-time data capture using ring buffers, although it includes no error

checking. In this example, process_data(bufptr) must execute in the same amount of time it

takes DMA to fill a single buffer or faster.

#include "edtinc.h"

main()

{

EdtDev *edt_p = edt_open("pcd", 0) ;

/* Configure four 1 MB buffers:

* one for DMA

* one for the second DMA register on most EDT boards

* one for "process_data(bufptr)" to work on

* one to keep DMA away from "process_data()"

edt_configure_ring_buffers(edt_p, 1*1024*1024, 4, EDT_READ, NULL) ;

edt_start_buffers(edt_p, 4) ; /* start 4 buffers */

for (;;)

{

char *bufptr ;

/* Wait for each buffer to complete, then process it.

* The driver continues DMA concurrently with processing.

bufptr = edt_wait_for_buffers(edt_p, 1) ;

process_data(bufptr) ;

edt_start_buffers(edt_p, 1) ;

}

Check compiler options in the EDT-provided make files.

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CDA CD 60 Especificaciones Pagina 13