nRF52840 undefined reference to `Serial'

[tamberg]

On MacOS with nRF52840 and Board Manager nRF52 v1.1.0 compiling

void setup() {
  Serial.begin(115200);
}

void loop() {
  Serial.println("hello");
}

results in

/Users/tamberg/Library/Arduino15/packages/adafruit/tools/arm-none-eabi-gcc/9-2019q4/bin/../lib/gcc/arm-none-eabi/9.2.1/../../../../arm-none-eabi/bin/ld: sketch/sketch_sep27c.ino.cpp.o: in function `setup':
/Users/tamberg/Documents/Arduino/sketch_sep27c/sketch_sep27c.ino:10: undefined reference to `Serial'
/Users/tamberg/Library/Arduino15/packages/adafruit/tools/arm-none-eabi-gcc/9-2019q4/bin/../lib/gcc/arm-none-eabi/9.2.1/../../../../arm-none-eabi/bin/ld: /Users/tamberg/Documents/Arduino/sketch_sep27c/sketch_sep27c.ino:10: undefined reference to `Adafruit_USBD_CDC::begin(unsigned long)'
/Users/tamberg/Library/Arduino15/packages/adafruit/tools/arm-none-eabi-gcc/9-2019q4/bin/../lib/gcc/arm-none-eabi/9.2.1/../../../../arm-none-eabi/bin/ld: sketch/sketch_sep27c.ino.cpp.o: in function `loop':
/Users/tamberg/Documents/Arduino/sketch_sep27c/sketch_sep27c.ino:22: undefined reference to `Serial'
collect2: error: ld returned 1 exit status
exit status 1
Error compiling for board Adafruit Feather nRF52840 Express.

[tamberg]

Add #include "Adafruit_TinyUSB.h"; to fix this issue (via S. Tiziano, A. Ambühl).

[tamberg]

Some background adafruit/Adafruit_nRF52_Arduino#653