Hello,
Matt <lists@xxxxxxxxxxxxxxx> has problems to post to the list. So I forward
his mail to the list to check the mailer and perhaps get feedback for him:
msg ->
Hi all,
When reading from or writing to an eeprom connected to channel A on my
ft4232 minimodule via i2c (mpsse mode), I occasionally fail to read the
ack from the eeprom and ftdi_read_data or ftdi_write_data return 0. As a
result the read or write transaction is regarded as a failure. Trying the
same operation again immediately may work ok. Other times, it may only
work ok after a few attempts. There seems no pattern to it at all.
I've set the latency timer to 2 using ftdi_set_latency_timer() and I've
had a look at app note AN232B-04. I understand that the function may
return due to several cases being met but given the fact that it seems
'random' makes me suspicious.
I'm calling ftdi_usb_purge_rx_buffer() after every call to
ftdi_read_data() but not flushing the tx.
Is it recommended behaviour to flush tx and rx after use? If so, wouldn't
this affect reading variable sized data from a peripheral (eg read a known
amount to obtain a data structure including the length of the data, then
read the remainder). I suppose this is another question... :-)
I notice that libmpsse changes the values of (struct
ftdi_context).usb_read_timeout and (struct ftdi_context).usb_write_timeout
directly however the ftdi.h API seems to indicate that you shouldn't need
to mess with these...
I see messages from the kernel relating to auto-suspend of the 4232
device. I'm not sure if these are indicative of something which could be
contributing to what i see or not. Any ideas?
Here's a small example output from dmesg when I'm running my program. It
looks innocent enough.
[28359.356403] usb 1-1.6: usb auto-resume
[28359.393363] usb 1-1.6: finish resume
[28361.391793] usb 1-1.6: usb auto-suspend
I'm using linux 3.1.0, libftdi 0.19 and libusb 0.1.12.
Has anybody seen anything similar?
Thanks,
-- Matt
--
Uwe Bonnes bon@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Institut fuer Kernphysik Schlossgartenstrasse 9 64289 Darmstadt
--------- Tel. 06151 162516 -------- Fax. 06151 164321 ----------
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