ch343g serial communication four-level version

The optocoupler isolation used in the multi-level version of CH343
is a bit opportunistic to be honest. It can even be said to be a cult
because VIO can support 1.8V, 2.5V, 3.3V and 5V. Just connect it directly and it can be achieved without optocoupler isolation. Multi-level
, but the problem is that some people reported that the equipment burned when using 1.8v. In actual measurement, the level was fine. I just didn’t know why it burned, so I made an optocoupler version.

In addition, it must be emphasized that the version without optocoupler must be connected to the select level shorting cap, otherwise the CH343G will most likely be burned directly in the access device! Please pay attention!

The size of the reduced version is 41mm * 15mm, which is already the smallest version I can shrink to.

In addition, the new version has no optocoupler and has cut off USB for the sake of size.

New content 0: The version without optocoupler adds a 100R current limiting resistor to prevent excessive IO current from burning the chip.

New content 1: The reduced version adds multiple 4.7K pull-up resistors to prevent annoying ESD phenomena.

New content 2: The reduced version and the version without optocoupler using RT9011-JGPJ6 LDO level are added to facilitate welding.

Make corresponding changes after a period of testing

A reduced version is as follows

There is no optocoupler as follows (the current limiting resistor is on the back, which may not be safe and can be easily damaged by knocking, so more soldering is required)