FreeRTOS FAT question

e12 wrote on Thursday, August 04, 2016:

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 SDCARD_WRITE_Task ,
X-axis is program execution time,
Y-axis is the time which the SDCARD_WRITE_Task is complete

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

As shown in graph SDCARD_WRITE_Task 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 ?**

rtel wrote on Thursday, August 04, 2016:

Sorry - I don’t understand your question. Could you try re-phrasing it,
although as this is your application, and we don’t know its structure,
what is being written, how good the driver is, whether the driver is
polling or interrupt driven, or what else the application is doing, it
is unlikely we will be able to provide an answer.

In the graphs I think I see a periodic write with a fairly fixed write
time, with a few longer writes that in between which are not on the same