ESP8266 Community Forum

- Thu Jun 02, 2016 2:38 pm #48472 Hi, I've never used the nodeMCU but have seen various posts and will offer some thoughts that may help.
Firstly I don't believe the 3.3V terminals were ever intended to power the unit, they were intended for outputs to sensors etc. They may well accept an input but I'm not sure what the onboard voltage regulator will think about this. I would use the 5V pin for now.
Secondly the ESP only draws about 70mA at boot which is not a lot for your 3A buck converter. I've seen various reports of larger 5V power supplies not working well with the ESPs. It might be worth putting an external load in parallel with the nodeMCU to give the buck converter a bit of work to do at start up see if that helps. Whilst this is not a good long term solution it help you fault find.

- Fri Jun 03, 2016 4:21 am #48500

Hi, I've never used the nodeMCU but have seen various posts and will offer some thoughts that may help.
Firstly I don't believe the 3.3V terminals were ever intended to power the unit, they were intended for outputs to sensors etc. They may well accept an input but I'm not sure what the onboard voltage regulator will think about this. I would use the 5V pin for now.
Secondly the ESP only draws about 70mA at boot which is not a lot for your 3A buck converter. I've seen various reports of larger 5V power supplies not working well with the ESPs. It might be worth putting an external load in parallel with the nodeMCU to give the buck converter a bit of work to do at start up see if that helps. Whilst this is not a good long term solution it help you fault find.

SOLVED! But no wiser which is not encouraging???

So you might want to look at the image below and the very ordinary 2N2222 circuits attached to the DIO. I disconnected the resistor on D10 (Native pin 3 mapped to TXD0 and GPIO1) and voila, normal boot. Something to do with leaving GPIO1 floating I guess. I am not an electronics person at all but I guess the resistor in series with the NPN transistor base was just pulling the pin a little close to ground. I have not seen anything written about a low logic in this pin at boot but I will put some code on the board this weekend and see if theGPIO is working OK!



Thanks for your input guys, much appreciated

Garry

- Sun Sep 30, 2018 3:36 pm #78446 Garry,

Did you ever figure out the underlying issue? I'm running into the exact same situation. D1 NodeMCU module boots and runs perfectly when powered through USB. When I apply power through to the +5V pin, and leave USB disconnected, it won't boot.
The power supply connected to +5V is regulated and capable of 2A. When powered with USB, I can use a basic 500mA charger and a thin-gauge USB cable, and it still boots and runs fine.

My module is the basic D1. The only IO pins that are connected to anything are D4 and D5.

When powered externally, I see a brief blinking from the blue LED every second or so, and that's it.
Thanks!

- Mon Oct 01, 2018 7:18 am #78449 Things I can think of:

• Power noise.
  Make sure power supply is regulated, stable and not too near to the antenna of the ESP.
• State of GPIO0, GPIO2, GPIO15 and or RESET is undetermined or wrong.
  GPIO0, GPIO2 and RESET have to be logically high (though pull up resistors) and GPIO15 logically low (pulled down) at boot.

The USB-serial convertor controls the RESET and GPIO0-lines with the auto program circuit; there's a possibility that it messes these up when not active or powered through the USB-port.

Assumption is the mother of all f*ckups. At least: that's what I'm assuming.