Content originally posted in LPCWare by fjrg76 on Thu Oct 11 13:04:35 MST 2012
Hi
Hope my answer is still valid for your project.
In order to use the alternate SWD pins you first need, through serial ISP, to upload a tiny program that (only) reprogram the alternate pins, so the next time, the microcontroller is aware of its new location.
After that, you need to include that tiny program (couple of source lines) in your application, so each time you reprogram the MCU, it always use the alternate location.