Wemos D1-Mini USB connection issues

[SpasT]

I bought few Wemos D1-Mini boards and all of them have connection to USB problems.
Found some posts over the internet, but no real solution. When I look in datasheet of CH340 I see that at pin16 of chip is VCC (5v from USB), but on the board this pin is connected to 3,3V. The simplest modification is to rise this pin from the board and connect it to USB VCC pin.
Now the connection is stable and no more disconnections.
I hope this can be usefull for others with the same issues.

[ThomasB]

Interesting solution. Your 5V conversion should also change the V3 pin, per the data sheet.

Why? The CH340 chip supports 3.3V VCC if the "V3" pin is also connected to 3.3V. When using 5V VCC, the V3 pin must be only connected to a .1uF cap (V3 is not connected to VCC).

ch340-1.jpg (67.75 KiB) Viewed 15380 times

ch340-2.jpg (102.08 KiB) Viewed 15380 times

- Thomas

[TD-er]

That's good info.
Maybe you could add this also to the Wiki, as I guess a lot more people will run into this.

Sounds like a new batch of so called Wemos D1-mini units has been sold to a number of AliExpress sellers so we will hear a lot more about these issues the upcoming weeks/months.

[grovkillen]

I added a link to this thread to the list of ESP "hardware": https://www.letscontrolit.com/wiki/inde ... P_hardware

I'm sorry for not being fast on the documentation, the GUI has been taking it's time + I have tried to get myself some income. It will be changing soon I hope.

[davecason]

Hi Guys,
I just read SpasT post about the voltage issue with newer Wemos D1 Mini's.

So is it safe to assume that newer boards need to have a jumper run from
the Wemos D1 Minis 5vdc input pin to a .1uF cap and then over to ....?

pin 4 labeled V3 on the CH340 chip itself or to
pin 16 labeled VCC on the CH340 chip itself

For that matter my existing board that I have are from 2018 so do you think
that might be the problem I'm having when trying to see the Wemos on my
USB port?

Cheers'
Dave

[TD-er]

A few things to check:

- Test other USB cable (!!) as some may have different lengths of the pads inside the connectors.
- Test in another USB port of the PC. Especially USB-3 ports may sometimes have connection issues due to shorter pad lengths inside the connector. Though the USB3 ports are capable of delivering higher currents, so switching from USB2.0 to USB 3.x ports may also make a positive difference.
- Does the USB device show up in Windows device manager?
- Is there a lot of stuff connected to the board? (thus drawing higher currents, or keeping GPIO-0 in a specific state during boot)