Tx2 SPI is not stable

Autonomous Machines Jetson & Embedded Systems Jetson TX2
#1

Hi

Now I’m using Tx2. And try to send data through SPI communication.

// Receive Data From SPI
	for(int loop = 0 ; loop < TESTLOOP; loop++)
	{
	
		iStart = cpuTimer();	// Check Time	
		ioctl(fd, SPI_IOC_MESSAGE(1), &tr);	// Send Data 

	}
	printf("Average elapsed time on CPU : %f\n",ElapsedTimeOnCPU/TESTLOOP);	// Print Time
	close(fd);

but the Time always different. 0.004 s , 0.002 s …

My test environment is short with SI SO (Loop back test)

Am I missing some code or need other HW ?

Thanks

#2

The SPI message is schedule by kernel scheduling process.
Could you run the jetson_clocks.sh to check if any improve.

#3

The timer you are using may not be precise enough for below 10 milliseconds. You can use the timer out of loop and calculate average value to have a more stable timing.