Does FREERTOS require CMSIS? I would like to convert an existing LPC1788 project to use FREEROTS. I cannot find any documentation on adding FREERTOS to an existing project.

No. FreeRTOS has been around much longer than CMSIS.

Do these links help? http://www.freertos.org/Creating-a-new-FreeRTOS-project.html http://www.freertos.org/porting-a-freertos-demo-to-different-hardware.html