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<Xogium>
here's a fun question... I've got a board which has 4 pins for uart. I'm not quite sure what the 4th pin means though... Typical gnd, rx, tx of course is there, but the 4th pin is a wakeup pin ? How does that even work ?
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<rfs613>
PMIC datasheet shows the PONKEYn connects to a "user push button" tied to GND
<rfs613>
pin described as "User power ON key (acrtive low with internal pullup)"
<Xogium>
hmm, makes sense
<rfs613>
there are some timing diagrams, showing how long it takes for various power rails to come up, after pressing PONKEYn
<Xogium>
really have to wonder why seeed exposed that one as a male header literally in the same row of pins as the 3 uart pins :D
<Xogium>
unless it means one can plop down a button on that male pin and somehow have a wake up button
<Xogium>
but I doubt it is that simple
<Xogium>
very intriguing design choice
<rfs613>
all this does is turn on power rails, from what I see
<rfs613>
i guess you can use this to put the board into very low power state, and have the button wake it back up
<Xogium>
yeah... Cause you can instruct the pmic to not immediately power the hardware and to require a button press. I've done it with another board of theirs which has an actual power button
<Xogium>
it makes sense this would be the same. Just the pin is... Well, I never expected that
<rfs613>
looks like it is someting like 15 ms to power up all the rails
<Xogium>
that, and it can also be used to resume from suspend
<Xogium>
I'm just having a really hard time picturing how you'd use that single pin, that's all
<rfs613>
i guess it was just easier to put a 1x4 pin header, rather than a separte 1x1 and 1x3...
<Xogium>
yeah, that must be it
<Xogium>
first time I saw that and I was really unsure what it was for