I did a few more measurements with a resistive probe: http://downloads.qi-hardware.com/people/werner/m1/rst/m1-5V-rp.jpg
The probe isn't exactly 1:10, so the voltages indicated are a bit too high. While at the desktop, the scope shows 4.91-4.92 V. My voltmeter shows 4.73-4.74 V. I then tried two atusb boards: http://downloads.qi-hardware.com/people/werner/m1/rst/m1-atusb1-rp.png http://downloads.qi-hardware.com/people/werner/m1/rst/m1-atusb2-rp.png Both caused the M1 to reset, as expected. But there are worse killers out there than puny atusb. Here's what a Ben and an Openmoko FreeRunner (both without battery) do: http://downloads.qi-hardware.com/people/werner/m1/rst/m1-ben-rp.png http://downloads.qi-hardware.com/people/werner/m1/rst/m1-gta02-rp.png We can see that it takes about 4 us for the voltage to drop to critical levels. So a current-limiting switch like the AP2142A with a short-circuit response time of 2 us should be able to catch this in time. - Werner _______________________________________________ http://lists.milkymist.org/listinfo.cgi/devel-milkymist.org IRC: #milkymist@Freenode
