Today, a little parcel with my atben/atusb boards arrived from tuxbrain. Among the boards were three atusb that had failed testing.
I had a quick look at them and spotted what are likely causes for the failures. Fortunately, each of them had a different problem. Nothing would be more boring than to have to see the same error over and over again ;-) The first board looks strong and healthy: http://downloads.qi-hardware.com/people/werner/wpan/tmp/atusb-bad1.jpg There's just one small flaw: the MCU should face the other way, as shown here: http://downloads.qi-hardware.com/people/werner/wpan/prod/atusb-compor.png That's not impossible to fix but it would be rather messy, so I think I'll save myself the trouble :) One to the second board: http://downloads.qi-hardware.com/people/werner/wpan/tmp/atusb-bad2.jpg Pick and place strikes again. This time by not placing a small resistor. The USB D+ signal goes through this resistor. Without it, the board can be flashed, it will power on when plugged into USB, but it won't be able to communicate. Should be easy to fix. The third one was a bit more difficult. All looked well until its troubles were revealed by the spectrum test, which checks the signal strength across the board's frequency range. [1] Closer examination revealed this: http://downloads.qi-hardware.com/people/werner/wpan/tmp/atusb-bad3.jpg You have to look at it from the right angle or the gap is hardly visible. A continuity test with a multimeter confirmed that the pin is not connected. This pin should connect to one half of the differential RF signal, between transceiver and antenna. Without it, a tiny bit of RF still makes it to or from the transceiver, but it's not really usable. Again, should be easy to fix. [1] http://downloads.qi-hardware.com/people/werner/wpan/prod/test.html#procedure If you're now examining your boards for undetected problems, please note that atben and atusb each have one unpopulated component. On atben it's C12, on atusb it's C16: http://downloads.qi-hardware.com/people/werner/wpan/tmp/atusb-c16-ok.jpg These are places where capacitors could be added for antenna tuning, just like the 0 Ohm resistors R1 (atben) or R3 (atusb) could be replaced with inductors. - Werner _______________________________________________ Qi Hardware Discussion List Mail to list (members only): [email protected] Subscribe or Unsubscribe: http://lists.en.qi-hardware.com/mailman/listinfo/discussion
