ESP8266 Community Forum

- Thu Jun 25, 2020 7:46 am #87648 Hi there!

I have a Wemos D1 Mini with an NTC and voltage divider. I have elaborate code that runs fine when the Wemos is stand alone and attached to my PC's USB. I also have a battery shield attached to a 3,7 LiPo battery. Whenever I hook this up to the Wemos D1 I observe the following behavior.

- First boot goes fine.
- After a few seconds I do a reset or interrupt the power and then the boot fails with:

Code: Select allFatal exception (0):
epc1=0x40100003, epc2=0x00000000, epc3=0x00000000, excvaddr=0x00000000, depc=0x00000000

I have tripple checked the solderings and tried pulling Hi GPIO0 and GPIO2, this aside from GPIO15 which I pulled low already.
I have used different sets of hardware, to no avail.

Please see attached a schema and a picture for reference.

Green wire is pulling GPIO15 low
Battery + is connected to shield out of view via underside of shield, minus can be seen
Purple wires is NTC.

Any suggestions would be very much appreciated.

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- Thu Jun 25, 2020 9:46 pm #87660 I suspect the initial boot up current draw is pulling your LiPo voltage too low.

Put a big fat capacitor in there as a buffer for the initial spike and see how you go

- Fri Jun 26, 2020 6:51 am #87665 Hi Davy,
Thanks, that sounds like something for me to explore. However, and I didn't mention this earlier: When i connect the ESP to USB/PC and I hook up the battery shield; i get the same erroneous behavior.

on your suggestion & as I am not an electronics guy by education; You are referring to a capacitor over input from battery into batt. shield, right? any suggestions on size (F)? Will investigate myself as well

Thanks a lot!

I suspect the initial boot up current draw is pulling your LiPo voltage too low.
Put a big fat capacitor in there as a buffer for the initial spike and see how you go

- Thu Jul 09, 2020 12:50 am #87822 Why repeated mentions of GPIO15? Its GPIO0 that controls booting or flashing. Yes 15 is involved and needs to be at the correct level too, but I have never know anybody have any problems with gpio15 when leaving it alone.

Google "ESP8266 boot pins" and make sure you are fully aware of the function of each.