After building the first boards, a strange error occurred, which only came up when operating the board via a simple USB power supply. After some research, the error could be isolated to a wrong voltage at the USB-serial IC. In this application the IC must not be operated with USB typical 5V, it must be supplied with 3V3. So the Pins V3 and VCC must be connected to 3V3.
After building the first boards, a strange error occurred, which only came up when operating the board via a simple USB power supply. After some research, the error could be isolated to a wrong voltage at the USB-serial IC. In this application the IC must not be operated with USB typical 5V, it must be supplied with 3V3. So the Pins V3 and VCC must be connected to 3V3.