On Sun, 6 Aug 2017 19:04:09 -0500 R0b0t1 <r03...@gmail.com> wrote: > On Sun, Aug 6, 2017 at 11:50 AM, <tu...@posteo.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.
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