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I recently designed my first Arduino Mega board with a CH340G as the serial IC. 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 full design including layout files, and a schematic excerpt showing the USB-to-Serial conversion:

USB to serial schematic

Currently only the SMD parts are on the board which got pick and placed (except the FE1.1s which will be soldered later.) Also the USB1 socket and the 5V input is soldered.

Any help would be appreciated.

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  • \$\begingroup\$ You need a CH340G driver in the target PC (which you may or may not have loaded). Try using a commercial Arduino which uses a CH340. If that works then you have a CH340 driver. Note that the FTDI drivers specifically do not work with alternative ICs. \$\endgroup\$
    – Russell McMahon
    Feb 1, 2021 at 11:32
  • \$\begingroup\$ @RussellMcMahon I have several arduinos with CH340 wich work so it is not a driver issue \$\endgroup\$
    – littlecat
    Feb 1, 2021 at 11:39
  • \$\begingroup\$ @RussellMcMahon I think the drivers automatically install on Win/Mac as of a few years ago. I set up an Ubuntu system a couple weeks ago and the drivers were already there (tested it on a clone Nano). There's an extra step adding permissions to the serial port, but that's nothing to do with the CH340. \$\endgroup\$ Feb 1, 2021 at 11:40
  • \$\begingroup\$ @SpehroPefhany Adding permissions to the serial port where? A general WIN permission or ...? \$\endgroup\$
    – Russell McMahon
    Feb 2, 2021 at 0:11
  • \$\begingroup\$ @RussellMcMahon Under Ubuntu, "sudo usermod -a -G dialout <username>" so that /dev/ttyACM0 can be accessed. Because ... \$\endgroup\$ Feb 2, 2021 at 0:20

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So you should confine your attention to the CH340G chip and immediate support components for present, as that is all that is required for it to enumerate.

I notice your schematic is missing the load capacitors for the crystal.

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  • \$\begingroup\$ Do you think that the load caps can be the issue? I have found articles which said I can use it without those but that might be the case. I can try to solder ceramic capacitors to each oscillator pin and ground, could that work? \$\endgroup\$
    – littlecat
    Feb 1, 2021 at 11:30
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    \$\begingroup\$ I would try that. You should also add them to the MCU, but that's not the issue. If the crystal circuit is okay, the 340G is getting power and the connections to the USB port are correct it should enumerate. \$\endgroup\$ Feb 1, 2021 at 11:36
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    \$\begingroup\$ Thanks, the caps were the issue \$\endgroup\$
    – littlecat
    Feb 1, 2021 at 11:46
  • \$\begingroup\$ Feedback appreciated! \$\endgroup\$ Feb 1, 2021 at 11:47

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