Dear Hartmut,
I increased SysTick to 10khz and the unwanted “sync to systick” (sympthom description, not description of found and understood error) reduced to 100us.
This is my config, can you see something missconfigured that explains the behaviour?
#define configUSE_PREEMPTION 1
#define configUSE_IDLE_HOOK 1
#define configUSE_TICK_HOOK 1
#define configCPU_CLOCK_HZ (SystemCoreClock)
#define configTICK_RATE_HZ ((TickType_t)10000)
#define configMAX_TASK_NAME_LEN (16)
#define configUSE_TRACE_FACILITY 0
#define configUSE_16_BIT_TICKS 0
#define configIDLE_SHOULD_YIELD 1
#define configUSE_MUTEXES 0
#define configQUEUE_REGISTRY_SIZE 8
#define configCHECK_FOR_STACK_OVERFLOW 0
#define configUSE_RECURSIVE_MUTEXES 0
#define configUSE_MALLOC_FAILED_HOOK 0
#define configUSE_APPLICATION_TASK_TAG 0
#define configUSE_COUNTING_SEMAPHORES 1
#define configGENERATE_RUN_TIME_STATS 0