Guru
Joined: 13/10/2014
Location: AustraliaPosts: 715
| Posted: 05:51am 04 Jul 2019 |
I went over the published circuits of the ZI and ZI2 boards to compare the reset circuits and it appears that (as they are currently setup up) the reset is derived from the ST-LINK controller in both V1 and V2 boards. The circuits appear almost identical and I'm no closer to understanding why the ZI2 board doesn't have a Power UP reset, I can only put it down to a change in the ST-Link function.
FYI I've been using the V2 (ZI2) board all day running at 480MHz, powering it on and off dozens of times and it's been faultless with the crude reset cap added, even the USB keyboard initialises every time now. So I've added a 22uf cap and plug-in link to the controller interface board in another unit I've built for someone else. If it ever fails and needs a new board then the ZI2 board will just plug straight in with only the reset link position needing to be changed. I now have a couple of spare ZI2 boards for the future.
It's all too hard.