Hi Alan,
Am 09.09.2012 15:00, schrieb Alan Stern:
But it now still works when afterwards plugging it into the 12.04 desktop.
Any clue? I'm not that into driver development...
Is this a firmware thing? The device is powered by USB only. Why does it
work on Ubuntu 12.04 after plugging it in once on Ubuntu 10.04?
Clearly the device doesn't like your RPi system. There's some sort of
hardware-level incompatibility; it may even be a question of available
power as Greg suggested. You should try adding a powered hub between
the computer and the device, just to see if it helps.
As for the desktop systems, there's no way to tell what's happening.
As far as I can see, the device should work okay with both of them all
the time. The only reason I can imagine for it not working with Ubuntu
12.04 is that the RPi somehow left it in a weird invalid state. But
that doesn't explain why plugging it into the other computer would
clear out that state.
By the way, I also get the impression that what matters is the computer
hardware and not the kernel version. That is, I bet if you would use a
different kernel on the RPi the device would still fail, and if you
would switch the kernels on the desktop machines then the behavior
would follow the machine, not the kernels.
Alan Stern
I don't think, that it was the RPi - because now it even works on the
RPi. Furthermore I had the problems before RPi with Ubuntu 12.04 on the
same desktop machine I used to run with 10.04.
Now with my RPi:
# dmesg:
[95542.802826] usb 1-1.3: new full-speed USB device number 34 using dwc_otg
[95542.907487] usb 1-1.3: New USB device found, idVendor=04d8,
idProduct=000a
[95542.907531] usb 1-1.3: New USB device strings: Mfr=1, Product=2,
SerialNumber=0
[95542.907550] usb 1-1.3: Product: CDC RS-232 Emulation Demo
[95542.907564] usb 1-1.3: Manufacturer: Microchip Technology Inc.
[95542.914838] cdc_acm 1-1.3:1.0: This device cannot do calls on its
own. It is not a modem.
[95542.915160] cdc_acm 1-1.3:1.0: ttyACM0: USB ACM device
[95543.000841] USB Serial support registered for FTDI USB Serial Device
[95543.004692] usbcore: registered new interface driver ftdi_sio
[95543.004721] ftdi_sio: v1.6.0:USB FTDI Serial Converters Driver
I still think, that some change in the code is responsible.
So - how can the kernel/drivers change the behavior of the device on
other machines? I don't get it. Is there some kind of firmware uploaded
by the drivers? It seems like some driver coming with 3.2.x left the
Board in a strange state. Maybe the newer driver(s) contain a new
"feature" introduced for other boards (initialization / firmware upload)
that doesn't jar with my "older" board ?
Do you think it's possible to get the "faulty state" if the board is
unplugged for a while? I think I never tried to plugin the device within
seconds after using it with my Ubuntu 10.04 machine. Can the "good
state" be lost if the board has no power for some time? Will try that
over night...
Whats the purpose and functionality of firmware in that case? Has that
chip some kind of Flash ROM? Afaik there's some basic "programming" on
the board because the chipset needs programming. (
http://www.microchip.com/pagehandler/en-us/family/8bit/)
I'll now continue with programming the interface with python and
pySerial - to see if it's stable.
Best regards,
Florian
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