T-beam: Reset After Power Loss (again)

1

reference:
https://meshtastic.discourse.group/t/solar-node-mounted-in-a-tree/5283/47
https://meshtastic.discourse.group/t/solar-powered-node-protected-vs-unprotected-li-ion-cel-does-it-always-need-a-reset/6343/11

setup:
t-beam is powered via usb on solar system.with other network gear. see: New User (sigh..) No MSGs Sent? MQTT and Other Qs - #2 by 65nw
to clarify, It is running off 110vac via a usb wall adapter so the power is on or off, no dc-dc or connection to batteries besides the 18650 on the tb. basically its on an unstable grid.

with clouds and winter, it has lost power several times. each time, after the 18650 dies, the tb requires a manual button push to bring back (even after the battery has recharged).

I have seen talk in the referenced threads that there is a 1 year time out that has been adjusted to something smaller.
its not off but in a deep sleep.
its still working but the screen is off.

I may be misunderstand that and not familiar with the definitions but it is not showing up on my network after all the other gear, routers etc. came back online a few days ago.

what is causing it?
Is there a setting to change this behavior ?
what if I take out the battery and power directly from a dc/dc converter:
…will it boot automatically when power is restored?
…will noise on the dc rail (without battery) cause rf interference?

when I went up and push the middle button, it said “Resuming…” for a few moments before going to the info screen.

signal-2024-01-12-223128
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2

There exist dedicated simple supervisory and reset ICs that provide a clean reset signal when power is restored and stable: https://www.instructables.com/Supervisor-Circuit-for-Your-Embedded-Projects/

3

Yes but not sure what to use from the t beam as a watchdog. An led pin, but nor sure if they are connected to an external pin. Will have to look at schematic.

Was hoping there was a setting to adjust that im not understanding. Is this really a limitation of the hardware?

4

Oh, figured it out.

Just pull the battery and let run off usb supply.
If you have external battery and a 5v regulator this should work as well.

Then when power is reatored, it just does a normal boot and there is no low battery standby recovery.

Lights out, lights on.

5

You didn’'t check the link provided. A dedicated supervisor IC works standalone. It monitors battery voltage and generates a reset signal all on its own. which you simply connect to the reset pin on the T-beam, no coding or free GPIO necessary. If you use the USB port for power, you power the USB+serial and the charging circuitry for the absent battery and a LED permanently, that’s a waste of sunshine. I have not seem a schematics for the T.Beam, but I presume it uses a linear regulator to supply 3.3V. Just presuming, but you’ll likely need twice the energy powering it through the USB port.