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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.

2
  • Do you have the pl2303 driver (CONFIG_USB_SERIAL_PL2303) enabled?
    – derobert
    Aug 10, 2015 at 20:24
  • I do, which makes me think I'm loading the wrong driver...and I am...doh!
    – MikeBman
    Aug 11, 2015 at 7:35

2 Answers 2

2

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.

-1

the driver is incorrect,ftdi driver is for Future Technology Devices the driver for prolific chip is pl2303 so you would need add the correct module to the kernel using insmod pl2303 or modprobe pl2303, but also confirm that vendor and product are correct according to the id table on the .c driver file, for some devices prolific does not support "fake copies" of the integrated circuits and you will need a patch or just add your vendor and product id numbers to it then compile it and remove the previous driver using rmmod pl2303 or modprobe -r pl2303. In order to get your vendor and product use lsusb, some times the ttyUSBn device is not created so you will need to created mknode and then chmod 666

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