Hello,
when doing MPSSE transfers, e.g. for JTAG, there is a constant need to read
back a fixed amount of data caused be the last write.
ftdi_read_data() doesn't guarantee to read back all requested data, but can
also return from a timeout, a short read and probably more causes.
In my code I have a wrapper readusb() around ftdi_read_data() to only return
when all data has been read, or some hard error happened:
unsigned int readusb(unsigned char * rbuf, unsigned long len)
{
int length = (int) len, read = 0;
int timeout=0, last_errno, last_read;
last_read = ftdi_read_data(&ftdi_a, rbuf, length );
if (last_read > 0)
read += last_read;
while ((read <length) && ( timeout <1000))
{
last_errno = 0;
last_read = ftdi_read_data(&ftdi_a, rbuf+read, length -read);
if (last_read > 0)
read += last_read;
else
last_errno = errno;
timeout++;
}
if (timeout >= 1000)
{
if (last_errno)
{
fprintf(stderr,"error %s\n", strerror(last_errno));
return EXIT_FAILURE;
}
}
if (read <0)
{
fprintf(stderr,"Error %d str: %s\n", -read, strerror(-read));
return EXIT_FAILURE;
}
return EXIT_SUCCESS;
}
Shouldn't some code like this be included in libftdi?
Bye
--
Uwe Bonnes [email protected]
Institut fuer Kernphysik Schlossgartenstrasse 9 64289 Darmstadt
--------- Tel. 06151 162516 -------- Fax. 06151 164321 ----------
--
libftdi - see http://www.intra2net.com/en/developer/libftdi for details.
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