- Fri Jul 07, 2017 8:03 am
#68028
OK, I've had to totally rethink this, since the person I'm building it for insists on using an off-the-shelf 4 x 4 matrixed keypad.
So how this is supposed to work: pressing the top left button enables the voltage regulator. The ESP starts up, sets rxd as a high output to latch the voltage reg on. By adding a transistro to the column driver it becomes truly open collector, so no phantom powering or leakage thru protection diodes. I reckon R11 being 50k should be safe enough to avoid damaging GPIO pins.
As before, please point out any obvious flaws.
@philbowles: note I took on board your point about switching the power as opposed to deep sleep.
So how this is supposed to work: pressing the top left button enables the voltage regulator. The ESP starts up, sets rxd as a high output to latch the voltage reg on. By adding a transistro to the column driver it becomes truly open collector, so no phantom powering or leakage thru protection diodes. I reckon R11 being 50k should be safe enough to avoid damaging GPIO pins.
As before, please point out any obvious flaws.
@philbowles: note I took on board your point about switching the power as opposed to deep sleep.
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