Why am I getting only 1v from 3v3 when I unplug ST-LINK

[KAsk.1]

When developing I'm using the ST-LINK to transfer my code to the stm32. All is well when it is plugged in but I'm only getting 1v from the 3v3 pin when I disconnect and run from usb. 5v is still 5v.

I've connected an hx711 with a load cell and also a 2x16 lcd but the lcd shuts down when unplugging the ST-LINK.

Does this mean I need an external power supply or can I use the 5v to get the 3v3?

[Ozone]

> Does this mean I need an external power supply or can I use the 5v to get the 3v3?

I suppose so.

Some while ago, I had the same problem with attached LCD display.

USB delivers up to 100mA to an attached sink. It can deliver up to 500mA if the device explicitly requests it - which your target device surely does not.

I assume you are using a Nucleo ar Discovery board, that has different power sources OR'ed via schottky diodes.

[KAsk.1]

I'm using the blue pill...

Would it be worth trying to add the 3v3 from 5v with a resistor?