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I've tried several different programs. A simple blinking program results in nothing. It works when connected into the programmer:

enter image description here

The ESP12 has a blue LED. The LED blinks only when connected to the programmer:

void setup() {
  pinMode(LED_BUILTIN, OUTPUT);
}

void loop() {
  digitalWrite(LED_BUILTIN, HIGH);level)
  delay(1000);                       // wait a second
  digitalWrite(LED_BUILTIN, LOW);
  delay(1000);
}

Other programs work as well (when plugged into the programmer). Although, when I take it off and attach a 3.2V LiFePO4 battery, the LED turns on faintly (no blink with the blink program uploaded). And other programs also do not work.

Is there something needed with the LiFePO4 battery? It measures a steady 3.34 V. Seller claims, "Continuous Discharge Current : 0.1A-1.0A." I measure 0.12 A.

Edit: Also tried connecting the battery to an ESP8266 dev board and the same no results happen.

enter image description here

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  • \$\begingroup\$ This may seem obvious or silly, but have you measured the cell voltage (under load) to ensure it is in range (3-3.6 V)? Or tried different cells? \$\endgroup\$
    – JYelton
    Sep 3, 2023 at 0:48
  • \$\begingroup\$ It measures a steady 3.34 V under load. I'll try a different battery in a second... \$\endgroup\$
    – adamaero
    Sep 3, 2023 at 1:03
  • \$\begingroup\$ Tried another battery. Measures 3.33 V and the same under load. \$\endgroup\$
    – adamaero
    Sep 3, 2023 at 1:06
  • \$\begingroup\$ Given that one of the pins is marked "5V" are you sure it will run off 3.3? \$\endgroup\$
    – Finbarr
    Sep 3, 2023 at 11:35
  • \$\begingroup\$ Update: works with ESP8266 dev board with the Vin pin powered off 3.3 V bench power supply. I tried the same with two ESP12Fs and again no result. So now I just read this: maciejmalecki.github.io/blog/…. \$\endgroup\$
    – adamaero
    Sep 3, 2023 at 14:37

1 Answer 1

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For the bare ESP to work, the enable pin needs to pulled high and pin 15 pulled low.

For the enable or CHPD pin, I soldered 10kΩ between Vcc and EN. For pin 15, I soldered a bridge to ground:

enter image description here

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    \$\begingroup\$ It is great to see you posting the solution; it may well help someone else with the same/similar problem. \$\endgroup\$
    – JYelton
    Sep 3, 2023 at 17:25

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