"Serial" USB output not working for atmelsam/arduino


I have a problem getting the Serial output on an adafruit feather M0 (atmelsam) up and running using platformio. I created a very simple sketch:

#include <Arduino.h>
int n=0;

void setup()

void loop()

Compiling and uploading this sketch using the Arduino GUI yields the expected result (fast running list of numbers) in the serial console.

Compiling and uploading using platformio in general works as well:

pio run -t upload
[Sat Jan 28 20:00:07 2017] Processing adafruit_feather_m0_usb (platform: atmelsam, board: adafruit_feather_m0_usb, framework: arduino)
Verbose mode can be enabled via `-v, --verbose` option
Collected 6 compatible libraries
Looking for dependencies...
Project does not have dependencies
Linking .pioenvs/adafruit_feather_m0_usb/firmware.elf
Checking program size
text	   data	    bss	    dec	    hex	filename
9712	    256	   1784	  11752	   2de8	.pioenvs/adafruit_feather_m0_usb/firmware.elf
Looking for upload port...
Auto-detected: /dev/cu.usbmodem1D1151
Forcing reset using 1200bps open/close on port /dev/cu.usbmodem1D1151
Waiting for the new upload port...
Uploading .pioenvs/adafruit_feather_m0_usb/firmware.bin
Atmel SMART device 0x10010005 found
Erase flash
done in 0.627 seconds

Write 9968 bytes to flash (156 pages)
[==============================] 100% (156/156 pages)
done in 0.067 seconds

Verify 9968 bytes of flash with checksum.
Verify successful
done in 0.007 seconds
CPU reset.
=========================================== [SUCCESS] Took 5.42 seconds ===========================================

But: Theres no output in the serial console.

Everything else seems to work fine if I upload code which does other things like blinking a LED.

I verified the described behaviour under MacOS and Linux using IDE 1.7.1 | Core 3.2.1.

What am I missing here?

Thanks & BR


Platform versions:

Platform atmelsam
Updating atmelsam @ 1.6.0: 	[Up-to-date]
Updating framework-arduinosam @ 1.10611.0: 	[Up-to-date]
Updating toolchain-gccarmnoneeabi @ 1.40804.0: 	[Up-to-date]
Updating tool-bossac @ 1.10601.0: 	[Up-to-date]

Please report an issue to Issues · platformio/platform-atmelsam · GitHub