LilyGo-T-SIM7080G Can't run when powered by USB charger / Battery

[Akira]

Hi,

I have tried the example "ModemMqttPulishExample"
I modify the APN, deviceID, Server IP, and some keys for the MQTT server,
Everything is working fine with PC / MAC, The data upload to the MQTT server perfectly.
But these only happen when connected to a PC / MAC
When I unplug the USB cable and plug it into a USB Charger
The board doesn't work anymore. Even I push the PWR key (1 ~ 3 sec.). The board still not running.
And then, I try to use the battery (18650) to power the board ( Switch On and press the PWR key for 3 sec. ). It still doesn't work.

I have tried three different types of USB chargers (USB Type A, Type C) and a power bank.
I checked some voltage ( VSYS = 5V, PMU_DCDC3 = 0.9V )
It seems the ESP32-S3 doesn't run when using the USB charger and the battery.

Any suggestions?

Thanks

[teastain2]

Hi, I do not have a LilyGo-T-SIM7080G but I looked into it and found this advice;
"7. If the power supply of the board cannot be turned on when the battery is connected,
please check that the mechanical switch beside the USB is turned toON,
and then press the board PWR for 2 seconds.
At this time, the board should start to work"

And this section of the schematic:

The main LilyGo-T-SIM7080G support page is here:
https://github.com/Xinyuan-LilyGO/LilyGo-T-SIM7080G

-Terry

[Akira]

@teastain2 Thanks Terry,
I checked the switch and power key, It doesn't work
The modem SIM7080G is still not powered on and the voltage for the SIM7080G remains 0.9V
Therefore I checked the PMU and I found the root cause.
The PMU initial is always failed when using the USB charger or the battery, And it will stuck at the while 1 loop
Just modify the initial procedure and remove the while 1 loop. And then the modem starts working !!

[teastain2]

@akira Great!
Thanks for replying!
-Terry