AWR1843: Timer delay implementation using Timer_create() Sysbios timer => not accurate

Good afternoon,

I implemented the solution shown in the following discussion:

AWR1642: Using watchdog function, but encountered a problem. - Sensors forum - Sensors - TI E2E support forums

I replaced the interrupt routine with the following:

void PeriodicFunc(UArg arg0)
{
     TmrMsgObj msg;
     msg.value = (unsigned long long) Cycleprofiler_getTimeStamp();
     Mailbox_post(gMmwMssMCB.tmrMsgsMbxHandle, &msg, BIOS_NO_WAIT);
}

And, in my reading task, I wrote the following:

Mss_createBiosTimer(400); // 400ms

int i;
TmrMsgObj msg;

for (i=0; i<10; i++) {
     Mailbox_pend(gMmwMssMCB.tmrMsgsMbxHandle, &msg, BIOS_WAIT_FOREVER);
     System_printf("msg.value=%u\n", (uint32_t) msg.value);
}

Then, using Excel, I setup this summary table, from the System_printf output to compute the difference between the machine cycles read, assuming each value is a machine cycle read after 400ms timer delay.

My question is why the values in the "value in ms" column are not that close to 400 ms as expected?

Trying other delays below 400ms leads to even worse results.

Thanks in advance.