DIY Compact Microcontroller Board

How to DIY an STC15 microcontroller development board with integrated automatic download function?

Design requirements:

1.To reduce size and space occupation, we can't use the DIP40+ZIF socket design. We can directly solder the TSSOP20 microcontroller, with 18 I/O pins which are sufficient, and use surface-mount components as much as possible.

2.Integrated automatic download function: use an 8-pin microcontroller to monitor download commands, and use a MOSFET to implement power cycling.

3.All I/O pins are led out using 2.54mm pin headers for easy expansion.

4.Use the wide-voltage STC 15W microcontroller, compatible with 3.3V and 5V levels, with jumper settings for switching.

5.Display section includes two 0.36-inch seven-segment displays and eight 0603 LEDs.

Schematic:

PCB:

The completed PCB.

Solder the components, ensuring voltage is normal before proceeding to prevent damage.

Using a neutral pen core is appropriate here.

Main MCU: STC15W408AS

Monitoring microcontroller and MOSFET

Used CH340 for USB to TTL conversion.

Power up after checking for any errors, OK.

Burning indication

Hello world in the microcontroller world!

Adding a seven-segment display is also OK.

After using it for a while, the automatic download function works smoothly. Its compact size makes it convenient to store.