Xiaofan Chen skrev: > On 7/4/06, palam.c wrote: > >> Hi all, >> >> I completed a PIC18F2550 USB board and it worked well >> with my desktop and few more desktops also. >> ** But It is not detected by my acer Laptop. (winxp) ** >> Its giving error that 'Unrecognized USB Device" >> Its a self powered device, i am not drawing any power from >> laptop also. >> How can i debug the issue ? >> > > Some possible problems/solutions: > 1) Insufficient Vusb bypass capacitors, at least 220nF but 470nF or > 1uF is recommended. > > 2) Try a different USB cable > > 3) Try to insert the device slowly to the USB port. I sometimes > have problem with PICkit 2 and the solution is to insert it slowly. > > What is the driver used (HID/CDC/customized/...)? Do you have > the service packs installed (SP1/SP2 )? > Just a note on 3/: If you look closely on the USB connector (cable end) you see that the two outer pins are longer than the two in the middle. The outer pins are +5V and ground, so the usbdevice are getting power a few milliseconds before the data signals in the middle gets connected. Maybe the device needs to settle after power up before it can establish a proper usb communication? -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist