I have question about freertos Fat I’m using iar compiler and stm32f427 scheduling method is preemptive, I‘m using the hal library, I’m using sdcard (sandisk extreme 16g)

The graph below relates to the execution time of the SDCARDWRITETask , X-axis is program execution time, Y-axis is the time which the SDCARDWRITETask is complete

http://imgur.com/a/MPYMX

As shown in graph SDCARDWRITETask is run every 80ms using vTaskDelayUntil,

http://imgur.com/P64neiK

As shown in graph SDCARDWRITETask is run every 40ms using vTaskDelayUntil

As you can see in the graph, This increased to periodically run time (incase 80ms is every 18 second, incase 40ms is every 9 second)

**My question this How is this problem occurs when any part of the problem?

This is the problem of the code? Or is it a hardware problem ?**