ESP8266 Community Forum

- Mon Oct 23, 2017 11:21 am #71132 What sort of decoupling capacitors would you recommended? The Lipo goes from 4.2v to 3.2v.

Also I still have not got any reply for my question. Would esp have any issues if the Lipo battery is kept on the back side of the board?

- Mon Oct 23, 2017 2:16 pm #71136 The Lipo (or any conductors) need to be kept away from the antenna section. If the Lipo is on the back of the module, behind the shielded area, it will have the minimum negative affect.

As far as bypass caps. I use surface mount components. Some ceramic. Tantalum, and least often electrolytic. Sometimes size is an important factor so it depends on what you can fit.

- Mon Oct 23, 2017 9:19 pm #71152

the esp8266 draws the max. current during rf-calibration.
during standard wifi-tx you can limit the current drawn by setting a lower tx-power.
If you use deep-sleep you can decrease current draw by using "RF_NO_CAL" and only use one RF_CAL cycle if wifi-connect fails.

Hey Schufti!

This is really useful to know - do you have links to examples? I want to add this to my own code!

- Tue Oct 24, 2017 12:47 am #71155 there is nothing much for examples.

In my sketch at a certain point I initialize WiFi and transfer my data.
If it is successful, I enter deepsleep with
ESP.deepSleep((945600000ull - micros()), RF_NO_CAL);
if it wasn't successful, I do it like this
ESP.deepSleep((945600000ull - micros()), RF_CAL);

If you use RF_DEFAULT it does (re)calibration only each n-th (10?) time according to soe text of espressif I can't find at the moment, but I never tried to verified this. I don't know where they store the count, so maybe a power cycle will reset or even a deep-sleep, maybe not a restart.
There is a report that since sdk 2.0 the RF_NO_CAL doesn't work any more, but I didn't find the time to verify that issue.