Fixes #1643 - no more freeze but now I have to understand why we go over

4k there

radio/src/opentx.cpp

@@ -3321,7 +3321,7 @@ uint16_t stack_free(uint8_t tid)
   for (; i<size; i++)
     if (stack[i] != 0x55555555)
       break;
-  return i*4;
+  return i;
 }
 #else
 extern unsigned char __bss_end ;

radio/src/targets/sky9x/syscalls.c

@@ -68,7 +68,7 @@ extern int _getpid ( void ) ;
 unsigned char *heap = (unsigned char *)&_end;
 extern caddr_t _sbrk(int nbytes)
 {
-  if (heap + nbytes < RAM_END-4096) {
+  if (heap + nbytes < RAM_END-8192) {
     unsigned char *prev_heap = heap;
     heap += nbytes;
     return (caddr_t) prev_heap;