Strange FTDI behavior

I suddenly have some very strange problems with the FTDI chip built into the BeagleBone.

It worked great at first.

But I plugged it in today, and it hung up my laptop, giving me errors like:

[ 4.720085] usb 1-2: device not accepting address 2, error -71

Completely locked up the host's USB subsystem too, along with everything connected to it!

So as not to hose up my machine, I instead plugged the beaglebone into an old sacrificial Linksys WRT that had a USB host port on it, and set it up with usbserial. I was able to see the FTDI chip, the tty, and even screen into it, but all that was coming out off the FTDI was an endless stream of ```````````````` characters.

I powered down the beaglebone, removed the SDcard from the board, and powered it back on. And the endless spew of ``````````s was coming out even with no root and no kernel on the board. So it seemed to be not coming from tty0o on the CPU, but rather from the FTDI itself. So I don't know, maybe the FTDI chip is fried, or maybe there's some way to field-reprogram it in case it's somehow lost its mind?

I saw some instructions on the wiki, which talked about changing the VID/PID of the FTDI, implying that the procedure reflashed the device, and also implied that it can only be done from Windows. I don't have any Windows machines so I'm not really able to just try the procedure to see if it fixes it.

I can live without the FTDI chip really; I've got serial dongles around here in case I need a console, and also JTAGs in case I need that too.

But I'm curious. Has anyone seen this particular FTDI failure mode? And, if so, does reflashing the FTDI chip fix it?




FTDI chips are very sensitive to electric noise (also they get burnt very often when working with electric hardware).
To reduce the noise you should reduce the usb cable to the minimun, half a meter is a maximun in most cases if
you don’t want to get into freeze, hung and related stuff.


There is no flashed code in the FTDI chip. You can reflash the EEPROM which tells the FTDI chip what it is supposed to look like. I have not had any reports of this issue.