bunnie 061284ec5f debugging BOOST mode glitch issue ... Here's an arcane bug for you: When powering down, the Spartan 7 3.3V I/O drivers will output a roughly 800us wide glitch as 3.3V falls below around 1.7V, if the 0.95V core voltage comes down first (which it does because we have an active discharge on 0.95V, but not on 3.3V). In this case, it's just wide and high enough to cause the BOOST mode line to engage, which takes the BOOST output and ties it to VBUS, which is just enough for the system to think you're powering it back on again. Which is not what you want when powering down. The ultimate fix was to put a heftier pull-down on the BOOST line so that it can't trip the BOOST output into the VBUS. Another option could be more active discharge FETs, but that would require a full board spin and we are already at certification, so we'll stick with the stronger pull-down on BOOST. It seems to be a robust fix in the worst corner cases we can find. The downside is that when powering an external USB device, you are burning an extra 30mW of power overcoming the pull-down, but typically, any external USB devices plugged into Precursor will burn far in excess of that, so the delta should be negligible.		2021-04-23 15:33:14 +08:00
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src	debugging BOOST mode glitch issue	2021-04-23 15:33:14 +08:00
Cargo.toml	bring benchmarks to v0.8 and record benchmark results	2021-04-07 00:45:11 +08:00