Wemos D1 powered by 5V pin won't boot

I am trying to build a simple LED strip driver with 2 PIR's on it. I created a little prototype board with some mosfets and a buck converter to go from 12v to 5v. The PIR sensors also need 5V so I thought it made sense to use that.

So eventually I want to hoop up a 12V power supply, so I won't be powering the Wemos through the USB connector.

I read about the pins that define how the wemos should be booted. So I connect D3 and D4 to 3.3V to have these pins high, and D8 to GND to have this low. This should enable boot from flash right?

I have tried three different Wemos board but they all won't boot. If I connect them with the usb cable everything is fine, esphome is started, to problem. But as soon as I want to use the external power supply it's all quited.

I measured between 5V and G on the wemos as well as D3 and G and D4 and G. All voltages seem to be good.

So what am I missing? Why wouldn't it boot?

It should make no difference how it is powered, if this schematic matches your board.

However, it is not correct that you must do anything special with the pins to upload software. It is a development board. Those instructions may apply to a raw ESP8266 module

You're right. I accidently connected one wire to TX instead of D1.

ESP chips can't read 5V. They are all 3.3V devices. Did you measure your dev board without anything attached other than USB and have a pin go high? That should tell you what voltage they output and accept as input.