The 16k FreeRTOS heap originally had all TCBs and stacks dynamically
allocated within it (plus semaphores and some other things). Now that
xTaskCreateStatic is used instead of xTaskCreate, the TCBs and stacks
are allocated statically and no longer use any of the FreeRTOS heap.
Therefore, the FreeRTOS stack can be shrunk by the amount that has been
made static. Furthermore, the TCBs and stack that are now static should
be placed in the .rtos_heaps section of RAM because this RAM is treated
specially by the bootloader (the bootloader executes from the first 16k
of RAM and loads the firmware into the section starting after the 16k).
After this patch the FreeRTOS heap (ucHeap) is 7200 bytes. The memory
available for the MicroPython heap is 54936 bytes (including GC overhead).
Damien George