ESP8266 Community Forum

That makes CE even less interesting to use.

I'd recommend using an external FRAM if frequent writing is required, they're absolutely cheap.

btidey wrote:Using deep sleep only is OK when timed operation is used but can make hardware a bit messy if external wake up is needed.

based on what references?
especially if external wake up is available this seems to be the most reliable solution.

It may be less interesting to use CE if you want to use state but as I said earlier there are many instances when this is not required. Over many different battery powered apps I have only needed to reference state once.

The reason I said this can get messy are as follows. If using timed as well as external then this must be combined with GPIO16. The rst input is pulled up via a medium size resistor plus a capacitor to ground. This further complicates driving it compared with the high impedance EN input which is totally under your control. For example if the external signal is level based then it can be low most of the time and a significant current is drawn through the pull up. Alternatively it has to be converted into a pulse. Of course it is not that difficult to deal with these if required, but my point is there are many cases where a simple external EN connection provides an elegant solution.

btidey wrote:For example if the external signal is level based then it can be low most of the time and a significant current is drawn through the pull up.

then you have chosen wrong polarity of external wake-up source ...
same holds true for CE: if wrong polarity you have to invert, drawing additional current ...