STM Blackpill doesnt work with external power supply
Hi, I know this might be a basic question, but I'm facing an issue while building my soldering station.
My setup consists of an STM32 Black Pill board connected to an SPI TFT display based on the ILI9341 controller.
The problem is that when I power the Black Pill through its USB port, the TFT initializes correctly and the UI is displayed every single time. However, when I power the board externally by supplying 5 V to the Black Pill's 5 V pin from a linear regulator, the display does not initialize. The TFT remains completely white with only the backlight turned on.
To verify that the STM32 is actually booting, I added a simple LED blink routine to the same firmware. Even when powered externally, the onboard LED blinks as expected, confirming that the MCU is running the code. The only issue is that the display never initializes and remains a blank white screen.
I'm trying to understand why the exact same firmware works perfectly when powered over USB but fails to initialize the ILI9341 when the board is powered through the external 5 V supply.
post regulator - 7805
preregualtor- a switching PSU.
essesntially the 5v regulator poweres the onboard LDO on the stm blackpill so I dont know where the problem arises from.