Hi, the code I use is based on the example code reduced to the minimum: 2 tasks that make 2 LEDs blink. The task using vTaskDelay(100) works as expected but the task using vTaskDelayUntil( &xLastWakeTime, xDelayMyTaskms) shows an unpredictable behaviour with 16bit ticks. With 32bit ticks also vTaskDelayUntil works on my system. The last time I used FreeRTOS on a similar uC before was with FreeRTOS7.x and i believe that it worked that days. But FreeRTOS tasks.c changed a lot in between. Did anyone else try the 16bit ticks with FreeRTOS9 on a 16bit uC? Hardware:  Microchip dsPIC33EV128GM104 Software:  MPLAB X IDE v3.30  XC16 (v1.26) compiler  FreeRTOS 9.0 FreeRTOSConfig.h ~~~

define configUSE16BIT_TICKS            1

~~~ Bug description:  vTaskDelay(100); // works as expected  vTaskDelayUntil( &xLastWakeTime, xDelayMyTaskms); // unpredictable behaviour FreeRTOSConfig.h ~~~

define configUSE16BIT_TICKS            0

~~~ -> Everything is ok. Task: ~~~ static void ledTask( void pvParameters ) {     TickType_t xLastWakeTime;     const TickType_t xDelayMyTaskms = pdMS_TO_TICKS(100);         int ledStatus = 0;         / Remove compiler warnings. */     ( void ) pvParameters;     /* Initialise xLastExecutionTime so the first call to vTaskDelayUntil()     works correctly. */     xLastWakeTime = xTaskGetTickCount();         for( ;; ) {         vTaskDelayUntil( &xLastWakeTime, xDelayMyTaskms);                 //vTaskDelay(pdMS_TO_TICKS(500) );                 if (ledStatus) {             LED1 = 0;             ledStatus = 0;         }         else {             LED1 = 1;             ledStatus = 1;         }     } } ~~~ Regards  Michael  

For some reason my reply to your post created a new thread, rather than replying here. This was my reply: Can you confirm that: 1) Your configTICKRATEHZ value is valid for using with pdMSTOTICKS (it is 1000 or less). 2) The calculation pdMSTOTICKS( 100 ) gives the expected value in both cases, and is not over/under flowing in one case.