Glad it worked!
If the TMCC receive test is successful, you can try transmitting a very simple 3-byte TMCC command - the emergency stop command (FE FF FF). Get something running on your layout, then run this program (again assuming the serial adapter is connected to Serial1:
#define TMCCPort Serial1
void setup() {
Serial.begin(115200);
Serial.println("E-stop test starting");
TMCCPort.begin(9600);
TMCCPort.write(0xFE);
TMCCPort.write(0xFF);
TMCCPort.write(0xFF);
}
void loop() {
}
If successful everything TMCC on the layout should shut down.