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By btidey
#90233 The difference could be down to the capacitor that is normally present on the reset line to ground. This together with a pull up resistor is used to provide a reset on power up.

If the capacitor is higher value on your 01S then the GPIO16 may be struggling to pull it low quickly during the wake up pulse and in some cases failing to pull it low sufficiently for a real reset.

If you are looking on the reset line with a logic analyser then this could show as a shortened pulse. A scope should show the reality of the slowed edges of the pulse.

If this is the case then you either have to replace the capacitor with a lower value, or maybe connect GPIO16 to the Enable (CH/PD) instead as this will have the same effect but there should not be a capacitor on this line. The caution here is to make sure the design uses a pull up on the Enable rather than being connected straight to Vdd.
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By EdHayes3
EdHayes3 wrote:Which orientation should the zener diode be placed, and what zener voltage is recommended? I had the same problem programming once I put this bodge wire on.

Used a high voltage zener (>6v zener voltage, schottky would also work) cathode towards GPIO16. Worked like a charm. Can program and use deepsleep. Strange how this isn't just added to the ESP-01