H743Zi2 Board


Author Message
KeepIS

Guru

Joined: 13/10/2014
Location: Australia
Posts: 715
Posted: 08:36am 03 Jul 2019      

Just got back to the workshop and looked at the reset line on the V1 ZI board:

At power up there is a tiny pulse and then the Reset line is held LOW for a delay of over a second before the Reset line is taken HIGH, in other words, it's in reset for a second or more after power up.

The ZI2 board goes instantly HIGH at power on = NO reset!

And yes, having the USB port connected causes a Reset at power UP, so it works under that condition, as does giving it a manual reset. The 22uf CAP from reset to ground holds the reset line low at initial power up and as the CAP charges the line goes high, and of course the Board starts up fine. Now to find out why this is different, I've rechecked my links and they all look ok but I'll go over it again
It's all too hard.