ESP8266 Boards under investigation.

This is just a list of boards we have been looking at for various projects.

LILYGO-T-OI

This board combines an 18340 rechargeable battery holder with a D1 mini board. There is a charging circuit for the battery. For our needs though, we are concerned with the following points:

The battery is connected via a transistor diode drop to the input of an ME6211 LDO circuit. The ME6211 has a dropout of 100mV. Assuming 300mV drop on the transistor there is basically no headroom on the battery (3.3V output + 300mV transistor drop + 100mV LDO drop = 3.7V = battery nominal charge voltage).
The circuit above wastes all voltage above 3.3V as heat
we would prefer to see a switcher circuit which allows the battery to run down to as low as 2V before shutting down.

D1 Mini Pro

https://ezmation.com/wifi/13-40-esp8266-d1-mini-wifi-with-usb.html

https://www.wemos.cc/en/latest/d1/d1_mini_pro.html

No components on the rear side makes this an interesting board to use as a module in a larger board. We would have preferred to see castellated holes for easy soldering to a main board.

ESP-01F

https://ezmation.com/wifi/44-esp-01f-ultra-miniature-wifi-module.html

The ESP-01F is the smallest wifi board implementation we have seen. It uses the ESP8285 for build in flash memory instead of using an external spi flash. It measures only 10mm x 11mm.

Trying to decide what firmware to run on your ESP board? Take a look at our ESP8266 firmware comparison.