Use mbed 5.14 For some reason I had to disable mbed-client-cli/ (multiple definition of `cmd' error at link time). Put a .mbedignore file in: $ cd /home/david/.platformio/packages/framework-mbed@6.51504.200716/features $ cat .mbedignore mbed-client-cli/* frameworks/mbed-client-cli/* see https://docs.platformio.org/en/latest/frameworks/mbed.html#ignoring-particular-components