Need help with custom board design (CH340G not working)

Hi, I recently designed my first arduino mega board with CH340G as a serial IC, but when I try to plug it into the computer (using USB1 on the board) I do not get a sound and the board is not recognised. I have burnt the bootloader already and I am getting the hearbeat blink on pin 13.
Here is my design

Any help would be appreciated

I have been thinking about using a CH340 on some of my own boards.

Did you breadboard the CH340 circuit before incorporating it into your design ?

No I have not, I used reference designs I could find on the internet.

Can you scope the Resonator and see if it's running.

Sadly I do not own a scope, but one of my friends suggested that I forgot the load capacitors, and I think that is the issue

Did the open pnp plans not have them?

Sometimes there is enough stray capacitance to make an oscillator circuit work without capacitors, but not always.

The datasheet for the CH340 would have been a good place to check before omitting components from a standard design. The datasheet does clearly show the capacitors in the recommended schematics.

You will also need to do this on the MCu and USB hub chips.

Are those resonators with internal caps ?

You will also need to do this on the MCu and USB hub chips.

The MCU works totally fine without it, and I have read somewhere that I don't need caps for it, and tha's why I forgot to add it to the other ones. Fortunately I can solder caps to those to fix it.

The only reason you would not need caps is if you are using resonators that already have them internally.

Are you using a crystal or a resonator?

Tom.. :slight_smile:

  • You have the chip's 3.3V output shorted to a 3.3V supply, which isn't good practice or what it's intended for.
  • Normally the chip's VCC is powered with 5V from the USB.
  • I think more research is needed. Check google's images here:

Thanks TomGeorge! +1 :astonished:

When I go to the link for the OPs schematic, I get this as the CH340G part of the circuit.

Tom.... :slight_smile:


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