Using a CP2103 to program an ATMEGA328-PU

[Grumpy_Mike]

@revolt_randy

Table 1 suggests it will handle 5.8V on any I/O pin.

The data sheet says about that value

Stresses above those listed may cause permanent damage to the device. This is a stress rating only, and functional operation of the devices at or exceeding the conditions in the operation listings of this specification is not implied. Exposure to maximum rating conditions for extended periods may affect device reliability.

Which is not the same thing as handling it. It might not work under those conditions, I fact it might not work with anything above the supply voltage.

You will see Table 3 doesn’t have a maximum input voltage, that doesn’t mean there is none, it means at the power rail.

I would also check that the DTR line is high when the converter is connected to a USB line and selected in a serial monitor.