Mon Oct 22 16:46:26 EDT 2012
Next: board powered from USB
- Power board form USB and disconnect PK2/FTDI.
- Drive the interpreter
Power from USB works with serial loopback. However, I need to unplug
it for about 5-10 seconds before replug. Maybe needs brown-out reset?
Hmm... it worked for a bit now not at all. Ok it does work when I
wait 5 seconds and plug it into a different hub, facing down. Maybe
solder issue, or a voltage issue. Maybe I should try with an LF?
It's very picky about the port it goes into. Plugging it directly
into the tower doesn't work either.. Only the powered hub.
I don't think it's the voltage. Very unpredictable behavior.
Probably some soldering issue.
It all works fine as long as its powered by the PK2. It seems really
just to crash. Maybe a pause at bootup would work?
I checked on the scope. Don't see much on the outside except for the
3.3V VUSB signal. It stays on for about a second, then discharges to
about 1V over a little over 2 seconds. This cycle repeats
indefinitely. I don't see anything happening to the supply voltage or
the reset. The device descriptor is received OK.
This might be related to the thing not working with just a serial
EDIT: Trying again using interactive PK2 it works for a bit, then it
Maybe it's time to switch back to uart and see what is actually going
EDIT: Trying some more things.
Added a startup delay: 0 for 0 for 0 for next next next, which seems to work.
EDIT: When I connect just the ground from PK2, it seems to run without
Disconnecting the ground then keeps it running. Nope, this is not
consistent. I just switch the hub's switch (unplug/replug) and it
starts OK. What can this be?
Touching the solder joints makes it crash.
If I don't send any data it lives longer.
Running from with PK2 with USB power disconnected works fine.
I can only make it crash by touching the oscillator connections.
Can this be caused by a floating input pin?
More weirdness. PK2 is now supplying 3V. I noticed this when trying
to close the USB 5V jumper while running.
After programming, pk2 give 4.3V
Running with that, after a while it gives up.
Stopping PK2, then starting again runs it at 3V.
First time no proper comm (bad-reply) 2nd time it works.
Could it be that the regulator is enabled, but the signalling voltage
is not 3.3V? EDIT: It is.
So everything seems to work at 2.7 and 3.6 V, but 4.3V doesn't work.
Maybe the power is just too unstable?