CP2102 USB to Serial Modules
OK, these particular modules have been around for a bit and there is simply no reason why they are still popping up all over the place having this overvoltage defect.
What is the issue?
The USB +5.0 volt Vcc line is connected directly to the CP2102 RST line, thus causing the CP2102s +3.3 volt internal regulator to latch horrible wrong. This is causing the regulator to dump out +4.2 volts to the 3v3 IDC pin connector, rather than the expected +3.3v.
Seeing that as most 3.3-volt devices have a maximum rating of +3.6 volts, the +4.2 volts is going to stress the silicon or outright kill the device connected to it.
I have several of these USB to Serial modules as both completely unbranded and as CJMCU types. So, this tells me several batches have been run, or even worse people making copies have all failed to test the design at the end.
• Whoever made these things, failed to build a simple prototype or do a small batch run to correct issues.
• EVERYONE SELLING THEM IS FAILING TO DO EVEN A SIMPLE QC SPOT CHECK or worse they know about the overvoltage issue on the +3.3 volt output and just do not give a fuck and keep selling them.
