How to directly power T-Beams with 3,3 V?

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21

Of course you’re right, I’ve jumped to the compiling without reading that thread carefully :roll_eyes:

22

I’ve replaced

https://github.com/meshtastic/AXP202X_Library.git

with

https://github.com/lewisxhe/AXP202X_Library.git

in platformio.ini, but now building fails saying:

src/Power.cpp:40:8: error: 'HasBatteryLevel' does not name a type
 static HasBatteryLevel *batteryLevel; // Default to NULL for no battery level sensor
        ^
src/Power.cpp:46:1: error: expected class-name before '{' token
 {
 ^
src/Power.cpp: In member function 'void Power::readPowerStatus()':
src/Power.cpp:151:9: error: 'batteryLevel' was not declared in this scope
     if (batteryLevel) {
         ^
src/Power.cpp: In member function 'bool Power::axp192Init()':
src/Power.cpp:245:13: error: 'batteryLevel' was not declared in this scope
             batteryLevel = &axp;
             ^
*** [.pio/build/tbeam/src/Power.cpp.o] Error 1
23

Did I say a quick round of tests? I think I meant to say an exhaustive round of tests followed by debugging and maybe reworking some code.

Lol

Pre production open source is sometimes hairy.

1 Like
24

Hi, I just wanted to say thanks for the valuable information on the PMIC and its use in the t-beam.
My use case is something completely different, but it helped a lot solving it.

I’m combining a t-beam with a pi zero W in a prototype (portable networked camera) and thus need to power the Pi and the t-beam from the battery. The pi needs 5V, but the 5V pin on the t-beam is VBAT as written in another thread (TTGO TBeam: Off-board USB? - #5 by dafeman) and therefore is not usable to power the Pi, especially if battery gets emptier.
So I soldered an external DC/DC buck converter (like those found in powerbanks) parallell to the t-beam and use that to power the pi.
To communicate with the t-beam, I connect it to the Pi’s USB host port. This worked well, but the DC/DC converter got very hot, basically because I fabricated a “charging loop”.

Adding
axp.enableChargeing(false);

to the t-beam firmware should fix the loop. That was actually what I was looking for, I’m still able to read out battery voltage and other info through the PMIC. The other solution would have been to physically disconnect the battery from the t-beam.