Re: [gentoo-user] USB device (ATtiny86 w. mcronucleus bootloader) not recognized ?

[Stefan Mark]

On Mon, 7 Aug 2017 17:44:31 +0200
tuxic@××××××.de wrote:

> On 08/07 11:29, Stefan Mark wrote:
> > On Sun, 6 Aug 2017 19:04:09 -0500
> > R0b0t1 <r030t1@×××××.com> wrote:
> >
> > > On Sun, Aug 6, 2017 at 11:50 AM,  <tuxic@××××××.de> wrote:
> > > > When I plug in such a little board into my PC, demesg
> > > > reports:
> > > > [ 1429.834140] usb 7-4: new low-speed USB device number 15 using
> > > > ohci-pci [ 1429.965142] usb 7-4: device descriptor read/64,
> > > > error -62 [ 1430.203151] usb 7-4: device descriptor read/64,
> > > > error -62 [ 1430.438161] usb 7-4: new low-speed USB device
> > > > number 16 using ohci-pci [ 1430.569151] usb 7-4: device
> > > > descriptor read/64, error -62 [ 1430.803174] usb 7-4: device
> > > > descriptor read/64, error -62 [ 1431.038184] usb 7-4: new
> > > > low-speed USB device number 17 using ohci-pci [ 1431.456157]
> > > > usb 7-4: device not accepting address 17, error -62
> > > > [ 1431.582204] usb 7-4: new low-speed USB device number 18
> > > > using ohci-pci [ 1432.000209] usb 7-4: device not accepting
> > > > address 18, error -62 [ 1432.000244] usb usb7-port4: unable to
> > > > enumerate USB device
> > >
> > > >
> > > > My first thought was: The micronucleus bootloaed is missing or
> > > > is defective...
> > > >
> > > > But plugging in the board into my Android tablet (the tablet
> > > > runs Lollipop and is nothing special at all beside being
> > > > rooted) via an OTG cable and using lsusb after that, it shows
> > > > Bus 001 Device 003 ID 16d0:0753 MCS Digistump DigiSpark
> > > >
> > >
> > > What the dmesg output is saying is that your USB hardware has
> > > reported a communication error to the driver. It is my guess that
> > > the ATtiny85 is not meeting the timing requirements for USB.
> > >
> > > Looking at the board there does not seem to be a crystal
> > > oscillator which most people would consider necessary for doing
> > > USB communication. This is an oversight on DigiStump's part and
> > > it is very likely you will not be able to fix the communication
> > > issues. You should contact them and tell them that your computer
> > > will not recognize their device and that you suspect it is
> > > because the clock is too inaccurate.
> > >
> > > >
> > > > What can I do to make this Digispark being correctly recognized?
> > > >
> > > > Thank you VERY much for any help in advance!
> > > >
> > >
> > > Three things:
> > >
> > > 1) Return the one you bought and get a new one. The ATtiny85's
> > > internal oscillator might be at the end of the bell curve but
> > > within manufacturer tolerance, which isn't enough to produce a
> > > USB signal close enough to the specified frequency. Expect the
> > > seller to pay for return shipping.
> > >
> > > 2) You can calibrate the oscillator using instructions in this
> > > application note:
> > > http://www.atmel.com/Images/Atmel-2555-Internal-RC-Oscillator-Calibration-for-tinyAVR-and-megaAVR-Devices_ApplicationNote_AVR053.pdf.
> > > This process still might not get you close enough.
> > >
> > > 3) Add a crystal oscillator to the ATtiny85 and change its fuses
> > > to use the oscillator. You will need to recompile the firmware if
> > > the crystal is a different frequency from the internal oscillator.
> > >
> > > It might work on your phone and not your desktop because of
> > > differences in the USB hardware (your phone's serial decoder in
> > > the USB hardware performs clock recovery but your PC does not) or
> > > because there are multiple things on a USB hub in your PC and the
> > > ATtiny85 is less accurate than those already present devices.
> > > Admittedly I'm surprised it gets most of the way to registering
> > > as a device and then fails, but I don't think the problem is with
> > > the drivers or your kernel.
> > USB uses a variant of non-return-to-zero for clock synchronisation,
> > that should™ take care of timing issues.
> > Actually, using microcontrollers without crystal for soft-usb is
> > fairly common (i have a bunch myself). As far as i understand (but
> > im no expert), trouble usually arises more from the improvised
> > level shifters than timing issues.
> > Anyway, i neither think there is a driver problem, i had a fair bit
> > of the messages myself, usually fixed by fixing the level shifter.
>
>
> Level shifters? What level shifters??? ;)
Oh, i see. Then i have to correct me, it seems that your board runs on
3v3 anyway (Which means i did not know those, only ones that look much
alike). A level shifter wont be necessary then.