The Teensy boards are great, but as they are they are not really useful for real development, as they lack proper SWD debugging. In “Modifying the Teensy 3.5 and 3.6 for ARM SWD Debugging” I have found a way to get SWD debugging working, at that time with Kinetis Design Studio and the Segger J-Link. This article is about how debug the Teensy with free MCUXpresso IDE and the $20 NXP LPC-Link2 debug probe:
Looking for a small, inexpensive ($25-30) ARM development board (say 120-180 MHz ARM Cortex-M4 with FPU, 512kB-1MB of FLASH and 256 KByte of RAM? Then have a look at the Teensy 3.5 and Teensy 3.6 by PJRC/Paul Stoffregen:
The only problem? it is not possible to debug it :-(. At least not in the traditional sense. This article is about how to change the board to use it with any normal SWD debugging tool e.g. Eclipse and the Segger J-Link :-).
For a project I want to use the Teensy 3.1 board (see “Hacking the Teensy V3.1 for SWD Debugging“) in USB CDC mode: that way the Teensy board can connect to the host and exchange data or attach a console to the Teensy board: that way I can connect the Teensy over USB to the host use the USB as communication interface: