The 1.5k pullup to D-

[koolatron]

Just a quick question..

I'm having a hard time getting Linux to recognize that I've got a device attached. The only thing that I know I'm not doing entirely properly is the 1.5k pullup - I've only got a 1k resistor on-hand and I didn't feel like creating a network to produce 1.5k. I surmised that since it's just a pullup, it's the level that matters and not the drive strength.

At any rate, dmesg begins spewing this sort of stuff:

Code: Select all

[18171750.692000] usb 1-6: new low speed USB device using ohci_hcd and address 23
[18171750.872000] usb 1-6: device descriptor read/64, error -110
[18171751.156000] usb 1-6: device descriptor read/64, error -110

I don't get any real feedback from the kernel besides that.

So: How critical is the value of the 1.5k pullup?

[christian]

The spec demands a relatively tight tolerance, but in practice the value does not matter too much.

The messages you see indicate that the host sees ONLY the pull-up resistor. There seems to be no (useful) communication with the device at all.

Are you sure your AVR is running on external clock and not with the internal RC oscillator?