I am using the softwareserial library with RX=TX for Pin 0 on XIAO Seeed but I get no output signal. When I am spliting the RX / TX on PIN 0 and PIN 2 e.g. it works as expected.
//RX=TX
#include <SoftwareSerial.h>
SoftwareSerial mySerial(0, 0, true); // RX, TX, true =inverted