I have designed a USB to a serial circuit that allows me to debug my circuit serially using a micro-USB connector.

The circuit is shown below.

enter image description here

However when I connect it to the PC, the device manager does say CH340G under ports, so I know it's not the drivers.

However, when I probed my TX line I found the following:

enter image description here

I see the TX line never goes "low". So that could be the reason why when I open up a serial monitor I do not get any data.

Does anyone know why this is happening? Why I cannot get my serial data displayed on my serial monitor?

EDIT 2: Output waveform for TX with the CH340G desoldered

enter image description here

  • 2
    \$\begingroup\$ You can re-assign the serial port pins in your code, but that doesn’t help with downloading new code. Best be getting the xacto knife out and patching the pcb. How the possibility of crossing the rxd and txd pins escaped you suggests you are way too optimistic for this type of work! \$\endgroup\$
    – Kartman
    Commented Oct 1, 2022 at 9:11
  • \$\begingroup\$ @Kartman last-minute additions are never a good idea! I probably misread the datasheet pinouts and somehow missed the schematic pinout too. Late-night designs are awesome... :( \$\endgroup\$
    – JoeyB
    Commented Oct 1, 2022 at 9:40

1 Answer 1


You have connected the TXD output of the CH340 to the TXD output of the ESP32.


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