When installing the SMD electrolytic capacitor pay attention to the positive and negative poles
The side of the SMD LED with the green mark is the negative pole
The solid semi-circular side of the electrolytic capacitor is the negative pole
When installing the SCM, make sure the first pin is in the right spot
Install the MCU in the direction of the flat angle on the mounting position of the MCU on the circuit board.
When soldering the SMD MCU, the USB host is mounted on the same side as the SMD component (the side with text), and cannot be mounted on the back side (no text).
J2 is used to select the power supply mode (USB power supply or external power supply). Use short circuit jumper cap to select.
When using external power supply, pay attention to the positive and negative voltages and voltage of the power supply is 5V DC.