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I'm using a raspberry pi to control a LED matrix display with a Prolific USB to serial cable (067b 2303). Using the default raspian image it works perfectly, however with a custom buildroot image (using rpi-buildroot) I'm unable to configure or use it.

Here are my steps thus far:

Linux recognizes the device but does not automatically load any drivers or attach it to /dev/ttyUSBx, so I use:

modprobe ftdi_sio

Which yields:

usbcore: registered new interface driver usbserial
usbcore: registered new interface driver usbserial_generic
usbserial: USB Serial support registered for generic
usbcore: registered new interface driver ftdi_sio
usbserial: USB Serial support registered for FTDI USB Serial Device

I don't see anything at /dev/ttyUSB* so I echo to new_id with prod and vendor IDs:

echo 067b 2303 > /sys/bus/usb-serial/drivers/ftdi_sio/new_id

Which yields:

ftdi_sio 1-1.2:1.0: FTDI USB Serial Device converter detected 
usb 1-1.2: Detected FIBU232AM 
ftdi_sio ttyUSBO: Unable to read latency timer: -32 
ftdi_sio ttyUSBO: Unable to write latency timer: -32 
usb 1-1.2: FTDI USB Serial Device converter now attached to ttyUSB0

When I try to change baud rate with:

stty -F /dev/ttyUSB0 115200

Which fails with:

ftdi_sio ttyUSBO: ftdi_set_termios FAILED to set databits/stopbits/parity 
ftdi_sio ttyUSBO: ftdi_set_termios urb failed to set baudrate 
ftdi_sio ttyUSBO: urb failed to clear flow control 
ftdi_sio ttyUSBO: failed to get modem status: -32
ftdi_sio ttyUSBO: ftdi_set_termios urb failed to set baudrate
ftdi_sio ttyUSBO: urb failed to clear flow control
ftdi_sio ttyUSBO: failed to get modem status: -32
ftdi_sio ttyUSBO: error from flowcontrol urb  

I found nothing for usb serial to configure.

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  • Do you have the pl2303 driver (CONFIG_USB_SERIAL_PL2303) enabled? – derobert Aug 10 '15 at 20:24
  • I do, which makes me think I'm loading the wrong driver...and I am...doh! – MikeBman Aug 11 '15 at 7:35
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Turns out ftdi_sio is the incorrect driver, I should be using pl2303. The following solved everything:

modprobe pl2303

And the device mounted and setup properly.

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