Yep, the ftdio_sio driver was loaded. 'sudo rmmod ftdio_sio' before
running my program to bang the bits resolved the 'usb bulk write
failed' failure.
I have some follow on question(s) for the list in light of this:
I have a regular uart serial port that I do want to use (need
ftdio_sio / usbserial modules loaded).
What is the desired way to ...
(a) ... allow ftdi_sio and libftdi to coexist peacefully? ... that
is, without having to unload the driver to do libftdi stuff, and
reload the driver to do usbserial (uart) stuff.
(b) ... allow bitbanging on one interface via libftdi as a regular user?
I added a new 'ftdi' group and did 'sudo chgrp ftdi
/dev/bus/usb/001/*' (there are 5 usb devices on this system -
which happens to be centos 6) and made sure the users I want to
have access are in group ftdi. Then I can use my program as a
regular user. I changed the permissions of all the usb devices
since ftdi_usb_open() tries them all looking for the device id.
It fails if it can't open one of the usb devices before a positive
match.
There's probably a better way? (yes, I could configure sudo
for a specific command or make my program setuid-root, but
those both seem less useful than my above hack - except
for adding permissions to _all_ usb devices)
As far as the -16... I'm guessing that is -1 * EBUSY.
The return value of ftdi_write_data is documented as:
Return values:
-666 USB device unavailable
<0 error code from usb_bulk_write()
>0 number of bytes written
Probably an EBUSY is getting returned somewhere if you drill into the
libusb code (possibly from poll(2) somewhere?).
Eric Schott wrote at 12:05 -0500 on Feb 10, 2017:
> *On Fri, Feb 10, 2017, John Hein wrote:*
> >
> > I'm trying to use bit bang on the fourth interface of the FT4232H.
> > See program below.
> >
> > I get an error I don't understand yet:
> >
> > write err: -16, usb bulk write failed
> >
> > What am I missing?
>
> I could not find -16 in my libusb.h.
>
> I have BITMODE_BITBANG working on FT4232H.. Things I have done
>
> - If using Linux, make sure the ftdi_sio driver is not loaded.
> You can blacklist the device (0x0403, 0x6011) or change the
> vendor/product values so Linux does not associate the
> chip with ftdio_sio kernel module.
>
> - I call ftdi_set_interface before calling ftdi_usb_open.
>
> > #include <ftdi.h>
> > #include <stdio.h>
> > int
> > main()
> > {
> > struct ftdi_context *ftdicx;
> > int rc;
> > unsigned char buf[1];
> >
> > ftdicx = ftdi_new();
> > rc = ftdi_init(ftdicx);
> > if (rc != 0)
> > printf("err: %s\n", ftdi_get_error_string(ftdicx));
> > rc = ftdi_usb_open(ftdicx, 0x0403, 0x6011);
> > if (rc != 0)
> > printf("err: %s\n", ftdi_get_error_string(ftdicx));
> > rc = ftdi_set_interface(ftdicx, INTERFACE_D);
> > if (rc != 0)
> > printf("err: %s\n", ftdi_get_error_string(ftdicx));
> >
> > /* 0xe => pin 0 is an input, pins 1-3 are outputs */
> > rc = ftdi_set_bitmode(ftdicx, 0xe, BITMODE_BITBANG);
> > if (rc != 0)
> > printf("err: %s\n", ftdi_get_error_string(ftdicx));
> >
> > buf[0] = 0x6; /* pin 1 & 2 => 1 */
> > rc = ftdi_write_data(ftdicx, buf, 1);
> > if (rc < 0)
> > printf("write err: %d, %s\n", rc, ftdi_get_error_string(ftdicx));
> > return 0;
> > }
>
> --
> libftdi - see http://www.intra2net.com/en/developer/libftdi for details.
> To unsubscribe send a mail to libftdi+unsubscribe@xxxxxxxxxxxxxxxxxxxxxxx
>
--
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