In my program I did exactly as instructed here: http://www.freertos.org/a00127.html
I include FreeRTOS.h and Task.h. I did #define INCLUDE_vTaskDelay 1 as well.
I want MS, and not ticks, so I have to use portTICKPERIODMS, but the program doesn't recognise portTICKPERIODMS. Why?
Which version of FreeRTOS are you using? If it is a version prior to V8 then the macro is called portTICKRATEMS.