The improved reset circuit for M1rc4 consists of two parts: the first part is the reset chip (APX803-40-SA), which is referenced to the 5V rail (in M1rc3, it was referenced to the 3V3 rail) and has a nominal threshold voltage of 4.0 V.
In my experiments with an M1rc3, I used the APX803-44-SA, which has a nominal threshold voltage of 4.38 V. This chip turned out to be too trigger-happy and would reset the M1 also when bus-powered USB devices were hotplugged. To test if the lower threshold voltage alone would protect us from such upsets, I reworked my M1rc3 to use the APX803-40-SA as well, then sent it rendering, and connected various USB devices. None of the mice (4) and keyboards (2) I tried would upset it. Also Bens and atusbs didn't bother it. Even most of my MIDI devices (3) cause no harm. The only device I tried that still makes it reset is the iCon i-Creativ. This shows that lowering the threshold had a beneficial effect, but it also shows that the second measure we took, namely the addition of a current-limiting power switch for the USB ports, is indeed necessary to ensure stable operation. - Werner _______________________________________________ http://lists.milkymist.org/listinfo.cgi/devel-milkymist.org IRC: #milkymist@Freenode
