Powering STM32 Blue pill through external source via micro USB

[Mshar.2]

Hello, I've a strange problem and I can't find the answer on internet.

I'm transmitting a data from UART2 of my STM32 Blue pill.

Its just one line :-

HAL_UART_Transmit(&huart2, (uint8_t*)Tx_msg, sizeof(Tx_msg), 100);

While using with ST-Link, it works.

When i connect micro usb from my laptop to Bluepill, it also works and transmits the data,

But when i connect micro usb from 5V charger/adapter to Bluepill, it doesn't work.

Bluepill is powered because LED is glowing but data isn't transmitted.

I tried with various chargers of different power, but it doesn't work.

Am i missing something?

[gbm · Accepted solution]

Check the GND connection between the BluePill and whatever you transfer the data to.

[Mshar.2]

Hello @gbm​ , thank you