Here you can find the setup, scripts and results of EMC testing.

Content

Hardware configuration
Test description
Test results - Radiated emission
Test results - Conducted emission
How to prepare the test
Standard test
Heavy test

Hardware configuration

iMX6 Rex EMC measurement - setup - cables 680px

Connected cables/devices

Power jack: +12V from an isolated source
SD card 1 (the one on the PCB edge): preloaded with Filesystem and used for booting
SD card 2 (the one under heatsink): used for read/write testing
RTC Battery: inserted in the holder
Ethernet: Ethernet loopback cable connected. Forced to 100Mb and used for ping test.
HDMI monitor: during the test, the monitor is connected but turned off.
2x USB memory stick: each connected through an extension cable. Both used during read/write test.
RS232: a null modem cable connected. During the test, the cable was terminated with an RS232 to USB converter.
SATA CFAST card (without the metal card holder): used for read/write testing
Headphones & Microphone: standard headphones connected to the headphones and microphone jack
Audio loopback: a cable connected between Line in and Line out
Wifi PCIE mini card: inserted, but not actively used. No antennas connected.
Modem: inserted, but not actively used. No antennas connected, no SIM card inserted.

Test description

The goal of this test was to check Radiated and Conducted emission of iMX6 Rex board while running at very high load. What was running:

CPU stress test
Memory stress test
GPU stress test (running a Full HD graphics test at rate 150 frames per second)
Linux GUI
Playing a video file
Playing an audio file
SD card test (SD card read & write stress test)
2x USB test (USB memory stick read & write stress test)
SATA test (CFAST SSD card read & write stress test)
Ethernet ping

Results

Radiated emission

*Note: Tested for EN55022B

Vertical polarization	Horizontal polarization
Running Linux Only	Running Linux Only
Vertical polarization	Horizontal polarization
Heavy Testing	Heavy Testing

Conducted emission

*Note: tested with VEP36US12

Power cable L1	Power cable N
Heavy Testing	Heavy Testing

Appendix

How to prepare the test

1. Download this file system (created based on Jasbirs blog), download this kernel and follow these steps to prepare SD card. 2. Insert the SD card to the edge SD card slot. 3. Update the u-boot to boot up from SD card and set few other parameters:

> setenv bootargs_mmc 'setenv bootargs ${bootargs} ip=192.168.10.91:::255.255.255.0 root=/dev/mmcblk1p1 rootwait video=mxcfb0:dev=hdmi,1920x1080M@60,if=RGB666 vmalloc=400M fbmem=28M fbcon=28M'
> setenv bootcmd_mmc 'run bootargs_mmc ; mmc dev 1; ext2load mmc 1 0x10800000 imx6rex-uImage-gpu-en-audio-fix-03-APR-2014 3915972; bootm 0x10800000'
> saveenv

4. Run test scripts (they are included in the file system, or you can download them here: Download Standard Test or Download Heavy Test). As script parameters use the directories where the devices are mapped (without /dev/) "./name-of-the-test.sh SATA_DIR USB0_DIR USB1_DIR MMC0_DIR" Here are examples how to run the scripts (in this example /dev/mmcblk1p1 is a filesystem device):

# ./emc-test1.sh sda1 sdb1 sdc1 mmcblk0p1

and the heavy test

# ./emc-test-all.sh sda1 sdb1 sdc1 mmcblk0p1

*Note: you may need to check where your devices are mounted. Use "fdisk -l". Here is an example:

# fdisk -l

Disk /dev/sda: 7998 MB, 7998455808 bytes
108 heads, 63 sectors/track, 2296 cylinders, total 15621984 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x001c2022

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1            2048    15621983     7809968   83  Linux

Disk /dev/mmcblk0: 3904 MB, 3904897024 bytes
4 heads, 16 sectors/track, 119168 cylinders, total 7626752 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0xc44e7f69

        Device Boot      Start         End      Blocks   Id  System
/dev/mmcblk0p1            2048     7626751     3812352   83  Linux

Disk /dev/mmcblk1: 1977 MB, 1977614336 bytes
61 heads, 62 sectors/track, 1021 cylinders, total 3862528 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

        Device Boot      Start         End      Blocks   Id  System
/dev/mmcblk1p1              62     3861421     1930680   83  Linux

Disk /dev/sdb: 16.2 GB, 16219373568 bytes
256 heads, 48 sectors/track, 2578 cylinders, total 31678464 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0xc3072e18

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1              48     7372799     3686376    6  FAT16

Disk /dev/sdc: 16.0 GB, 16008609792 bytes
255 heads, 63 sectors/track, 1946 cylinders, total 31266816 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

   Device Boot      Start         End      Blocks   Id  System
/dev/sdc1              32    31266815    15633392    c  W95 FAT32 (LBA)

The Standard test script

#!/bin/sh

mountDevice() {
  mount /dev/$1 /media/$2
  cat /etc/mtab | grep -F "/dev/$1 /media/$2"
  if [ "$?" -eq "0" ]; then
    echo "$2 mounted"
  else
    echo "$2 not mounted"; exit 2
  fi
}

# mount devices a test a status
mountDevice $1 sata
mountDevice $2 usb0
mountDevice $3 usb1
mountDevice $4 mmc0

# tell the X applications where they should run
export DISPLAY=:0

# run X window - wait for the procces
service lightdm start

# connect ethernet loopback and force the ethernet to 100Mbit
mii-tool -F 100baseTx-HD

# play a video file in an infinite loop
echo 0 > /sys/class/graphics/fb2/blank
sudo -u "ubuntu" xfce4-terminal --geometry=70x20+100+10 -x mplayer -vo fbdev2:/dev/fb2 -vf scale -zoom -loop 0 -xy 1024 /home/ubuntu/Clou$

# ping
sudo -u "ubuntu" xfce4-terminal --geometry=70x25+100+600 -x ping 192.168.10.1 &

# top
sudo -u "ubuntu" xfce4-terminal --geometry=90x50+900+10 -x top &

proceed=1
file1="blackbird.wav"

while [ $proceed -eq 1 ]
do

  cp1_done=`ps cax | grep $cp1_pid | grep cp`
  if [ -z "$cp1_done" ]; then # run cp only if previous cp is done
    cp /media/usb0/$file1 /media/sata &
    cp1_pid=$!
    echo "started cp from usb0 to sata"
  fi

  cp2_done=`ps cax | grep $cp2_pid | grep cp`
  if [ -z "$cp2_done" ]; then # run cp only if previous cp is done
    cp /media/usb1/$file1 /media/mmc0 &
    cp2_pid=$!
    echo "started cp from usb1 to mmc0"
  fi

  aud_done=`ps cax | grep $aud_pid | grep aplay`
  if [ -z "$aud_done" ]; then
    aplay -D hw:0,0 /home/ubuntu/blackbird.wav &
    aud_pid=$!
    echo "started play audio"
  fi

done

# kill all procceses if Ctrl+C detected
trap '$precced=0; kill $cp1_pid $cp2_pid &aud_pid;' 2
sleep 10000

The Heavy test script

#!/bin/sh

mountDevice() {
  mount /dev/$1 /media/$2
  cat /etc/mtab | grep -F "/dev/$1 /media/$2"
  if [ "$?" -eq "0" ]; then
    echo "$2 mounted"
  else
    echo "$2 not mounted"; exit 2
  fi
}

# mount devices a test a status
mountDevice $1 sata
mountDevice $2 usb0
mountDevice $3 usb1
mountDevice $4 mmc0

# tell the X applications where they should run
export DISPLAY=:0

# run X windows - wait for the procces
service lightdm start

# connect Ethernet loopback and force the ethernet to 100Mbit
mii-tool -F 100baseTx-HD

# gpu test
cd /root/gpu-viv-bin-mx6q-3.10.9-1.0.0-hfp/opt/viv_samples/vdk
./tutorial7 &
gpu_pid=$!
cd

# play a video file on the lvds display
echo 0 > /sys/class/graphics/fb2/blank
mplayer -vo fbdev2:/dev/fb2 -vf scale -zoom -loop 0 -xy 1024 -really-quiet /home/ubuntu/Clouds.avi &
vid_pid=$!

# stressapptest - testing sata, 2x usb, sd card, 1 thread CPU, 1 thread memory
stressapptest  -f /media/sata/tmp-file1 -f /media/usb0/tmp-file1 -f /media/usb1/tmp-file1 -f /media/mmc0/tmp-file1  -s 600000 -M 50 -m 1 $
str_pid=$!
echo "Stressapptest: " $str_pid

# play a audio file
mplayer -loop 0 -really-quiet /home/ubuntu/blackbird.wav &
aud_pid=$!

# ping
ping 192.168.10.1 &
ping_pid=$!

# top
top
top_pid=$!


# kill all procceses if Ctrl+C detected
trap '$procced=0; kill $gpu_pid $vid_pid $aud_pid $str_pid $ping_pid;' 2
sleep 10000

Note: If the LVDS monitor is not included in the setup comment out these lines:

#echo 0 > /sys/class/graphics/fb2/blank
#mplayer -vo fbdev2:/dev/fb2 -vf scale -zoom -loop 0 -xy 1024 -really-quiet /home/ubuntu/Clouds.avi &

And add this line (to disable LVDS):

# echo 1 > /sys/class/graphics/fb2/blank

iMX6 Rex Projects

FREE Schematic & PCB for Download

EMC testing (including the script examples)