iMX8M Industrial EMC testing

Electromagnetic compatibility results for iMX8M Industrial Development Kit are presented on this page. Test setup and scripts are described in details.

These tests were performed with setups using the standard hardware and software configurations of the web shop development kits.

The certificate measurements were carried out on the iMX8M Industrial Development Kit in Pro version as this configuration delivers the best price-performance ratio and is the most popular amongst the customers. Other configurations - Max and Basic were also tested both passing the EMC radiated and conducted emmissions Class B norm. As the differences in the results were negligible, this web page focuses on the certificated measurements of the Pro configuration of the development kit.

The certificate document contains numerous different measurement as described in the ETSI EMC standards. This wiki page highlights and discuses only the most important results. All the details can be found in the EMC certificate and dedicated downloads folder.

The measurements were performed in an accredited test laboratory. After passing all the requirements described in the harmonised standard ETSI EN 301 489-17, the EMC certificate with conformity assessment and test reports was issued for the iMX8M Industrial Development Kit.

Connected cables/devices

• Power source: +5V 40W power supply used for input voltage
• Storage device: eMMC Flash memory soldered on module used for booting, filesystem operation and script storage
• Ethernet: 1m long CAT Ethernet loopback cable connected. Forced to 100Mbps and used for ping test
• one of these video output options was used at a time:
  • DisplayPort (M) interface used with LCD monitor connected: Full-HD output video stream generated and sent to LCD monitor via 1.5m long DisplayPort cable, with ferrite beads added (Würth Elektronik P/N: 742 711 32). The output signal forced to be continuously generated, contributing to EMC spectrum, monitor was plugged into mains, turned on, and laid flat on the floor to minimise its impact on results. Used LCD monitor: 24" LG LG24BK550Y 1920×1080 px
  • HDMI interface used with LCD monitor connected: Full-HD output video stream generated and sent to LCD monitor via 1.5m long HDMI cable, with ferrite beads added (P/N: Würth Elektronik 742 758 15). The output signal forced to be continuously generated, contributing to EMC spectrum, monitor was plugged into mains, turned on, and laid flat on the floor to minimise its impact on results. Used LCD monitor: 24" LG LG24BK550Y 1920×1080 px
  • LCD Display: Newhaven LVDS Capacitive Display Set with 1024x600 resolution. The display was mounted on top of the development kit with metal standoffs, active and displaying continued video stream coming from the camera thus contributing to EMC spectrum. LCD P/N: NHD-10.1-1024600MB-LSXV-CTP
• 2x USB 3.0: SanDisk Ultra Flair 16GB USB 3.2 Gen 1, each connected through a 1m long USB 3.2 Gen 1 extension cable (Molex P/N: 0687890035). Both used during read/write test
• USB-C: Kingston DataTraveler 80 32GB USB 3.2 Gen 1, connected through USB-C extension cable (Cable P/N: FCR72003)
• Camera: Digilent MIPI-CSI Camera Set plugged to the baseboard, recognised by the kernel, active and capturing video stream. Ferrite bead added on the ribbon cable connecting the kit and the camera module (P/N: Würth Elektronik 742 721 1)
• CAN: CANbus Module inserted, not actively used during testing. CAN cable not connected
• WiFi and Bluetooth: Soldered directly on COM, placed in active scanning and discoverable mode, contributing to EMC spectrum. Depending on the temperature range, the default CM-276NF or alternative SPB228-D-3 module was populated. Two antennas plugged in and connected
• Console cable: Micro USB extension cable used only to setup the development kit, not plugged in during the measurements
• SD card: SD card (SanDisk) plugged in and used during read/write test
• Microphone: Microphone connected via 1.5m long cable, not actively used
• Headphones: Headphones connected via 2m long cable, not actively used
• Speakers: Line Out connected via 2m long cable, plugged into the mains and not actively used

Testing conditions and results

All the results were measured in compliance with the emission limits for FCC / ETSI Class B (EMC standards EN 55032B and EN 61000). Class B devices are suitable for both residential and industrial applications as the norm standards use more restrictive limits.

iMX8M Industrial Development Kit Pro - Testing peripherals and external LCD display – PASSED

Test description:

• development kit in standard webshop Pro configuration:
  • iMX8M Industrial Module Pro in Commercial temperature range
  • iMX8M Development Baseboard in Extended temperature range
• CPU heavy testing threads using stressapptest
• DDR4 memory heavy testing threads using stressapptest
• Ethernet loopback cable used for network testing
• running heavy read/write testing for USB devices and SD card
• Digilent MIPI-CSI Camera Set capturing video stream
• LCD Newhaven LVDS Capacitive Display Set actively used
• two antennas with cables
• cables and devices plugged in but not actively used:
  • USB-C
  • Audio jacks
• peripherals heavy testing script used
  
  

Radiated Emissions

The measurement starts with peak detection by scanning the whole frequency spectrum. This initial detection is plotted with the red curve. Afterwards the highest peaks were pointed and measured more thoroughly by quasi-peak method. These real measured values of the radiation are displayed with the red crosses. The graph shows the setup passed the strict residential 55032-B limit represented by the red highlighted line.

These results prove that iMX8M Industrial Development Kit, even under heavy load, meets the stricter limits even if no enclosure is used.

Radiated emissions in lower band 30MHz - 1GHz

Antenna used: ETS Lindgren 3143B BiConiLog Antenna 30 MHz to 1GHz

Horizontal polarisation		Vertical polarisation

Radiated emissions in higher band 1GHz - 6GHz

Two plots displaying the power density are used to show results in higher bands. Similar to lower frequencies red curve represents quasi-peak values. Class B limits applied for quasi-peak measurements are plotted as the higher placed red line 55032,RF,1-6GHZ,PK,B.LIN.
Green curve depicts average-power values. Threshold for average-power measurement is shown with the lower placed limit line called 55032,RF,1-6GHZ,AV,B.LIN.

Antenna used: ETS Lindgren 3119 Horn Antenna 400MHz to 6GHz
Note: Emissions in the 2.4 and 5 GHz band are part of the working frequency band, they will be disregarded from the evaluation of results.

Horizontal polarisation		Vertical polarisation

Conducted Emissions

The measurement was performed by a clamp indirect method.
Enhanced input power protection on the iMX8M Development Baseboard does not allow direct line impedance stabilisation network (LISN) method to be used.

iMX8M Industrial Development Kit Pro - Testing module and DisplayPort output - PASSED

Test description:

• development kit in standard webshop Pro configuration:
  • iMX8M Industrial Module Pro in Commercial temperature range
  • iMX8M Development Baseboard in Extended temperature range
• CPU heavy testing threads using stressapptest
• DDR4 memory heavy testing threads using stressapptest
• Ethernet loopback cable used for network testing
• running heavy read/write testing for USB devices and SD card
• Digilent MIPI-CSI Camera Set capturing video stream
• DisplayPort output tested in Full-HD 1920x1080 resolution
• two antennas with cables
• cables and devices plugged in but not actively used:
  • CANbus Module
  • USB-C
  • Audio jacks
  • JTAG programmer
• module heavy testing script used
  
  

Radiated Emissions

The measurement starts with peak detection by scanning the whole frequency spectrum. This initial detection is plotted with the red curve. Afterwards the highest peaks were pointed and measured more thoroughly by quasi-peak method. These real measured values of the radiation are displayed with the red crosses. The graph shows the setup passed the strict residential 55032-B limit represented by the red highlighted line.

These results prove that iMX8M Industrial Development Kit, even under heavy load, meets the stricter limits even if no enclosure is used.

Radiated emissions in lower band 30MHz - 1GHz

Antenna used: ETS Lindgren 3143B BiConiLog Antenna 30 MHz to 1GHz
Note: Results in higher band 1GHz - 6GHz were very similar to the measurements performed on the previous testing setup

Horizontal polarisation		Vertical polarisation

iMX8M Industrial Development Kit Pro - Testing module and HDMI output - PASSED

Test description:

• development kit in standard webshop Pro configuration:
  • iMX8M Industrial Module Pro in Commercial temperature range
  • iMX8M Development Baseboard in Extended temperature range
• CPU heavy testing threads using stressapptest
• DDR4 memory heavy testing threads using stressapptest
• Ethernet loopback cable used for network testing
• running heavy read/write testing for USB devices and SD card
• Digilent MIPI-CSI Camera Set capturing video stream
• HDMI output tested in Full-HD 1920x1080 resolution
• two antennas with cables
• cables and devices plugged in but not actively used:
  • USB-C
  • Audio jacks
• module heavy testing script used
  
  

Radiated Emissions

The measurement starts with peak detection by scanning the whole frequency spectrum. This initial detection is plotted with the red curve. Afterwards the highest peaks were pointed and measured more thoroughly by quasi-peak method. These real measured values of the radiation are displayed with the red crosses. The graph shows the setup passed the strict residential 55032-B limit represented by the red highlighted line.

These results prove that iMX8M Industrial Development Kit, even under heavy load, meets the stricter limits even if no enclosure is used.

Radiated emissions in lower band 30MHz - 1GHz

Antenna used: ETS Lindgren 3143B BiConiLog Antenna 30 MHz to 1GHz
Note: Results in higher band 1GHz - 6GHz were very similar to the measurements performed on the previous testing setup

Horizontal polarisation		Vertical polarisation

Immunity - Radio frequency electromagnetic field 80MHz - 6GHz

		Test results / EUT side exposure results
Frequency range (MHz)	Antenna polarization	Front	Back	Left	Right
80 – 1000	V	PASS	PASS	PASS	PASS
1000 – 6000 (*)	V	PASS	PASS	PASS	PASS
80 – 1000	H	PASS	PASS	PASS	PASS
1000 – 6000 (*)	H	PASS	PASS	PASS	PASS

Note (*): The exclusion bands are applicable in this frequency range.

Conducted emission - wired network ports

Immunity - Electrostatic discharge

Discharge type	Discharge level (kV)	Discharge location	Number of discharges per location for each polarity (number of locations)	Performance criterion	Test result
Direct air discharge	±8	Non metallic parts	10 (17)	B	PASS
Direct contact discharge	±4	Metallic parts	10 (9)	B	PASS
Indirect contact discharge	±4	HCP - Front	10	B	PASS
Indirect contact discharge	±4	HCP - Left	10	B	PASS
Indirect contact discharge	±4	HCP - Right	10	B	PASS
Indirect contact discharge	±4	HCP - Rear	10	B	PASS
Indirect contact discharge	±4	VCP - Front	10	B	PASS
Indirect contact discharge	±4	VCP - Left	10	B	PASS
Indirect contact discharge	±4	VCP - Right	10	B	PASS
Indirect contact discharge	±4	VCP - Rear	10	B	PASS

Note (*): The EUT was without exposed conductive surfaces.
Abbreviation: HCP - Horizontal coupling plane
Abbreviation: VCP - Vertical coupling plane

Preparing the test

Boot device and software

These measurements were performed with boards using the actual hardware and software configuration of the web shop development kits.

eMMC Flash memory was selected as a booting device for all the measurements. U-Boot settings were not adjusted as the default configuration was used.

Running the script

Plug the development kit into mains and connect it to the controlling PC via console. Before the first time usage of the script, permissions need to be granted by the following command:

chmod +x imx8m-voipac-peripheral-test.sh

Testing scripts command consists of the following arguments:

• the first parameter - configuration of tested development kit (Max, Pro or Basic)
• the second parameter - USB drive 1 location
• the third parameter - USB drive 2 location
• the fourth parameter - SD card location

One of these commands can be used during EMC testing as shown below:

• iMX8M Industrial Development Kit Max:

./imx8m-voipac-peripheral-test.sh -max sda1 sdb1 mmcblk1p1 | tee -i imx8m-emc-testing.log

• iMX8M Industrial Development Kit Pro:

./imx8m-voipac-peripheral-test.sh -pro sda1 sdb1 mmcblk1p1 | tee -i imx8m-emc-testing.log

• iMX8M Industrial Development Kit Basic:

./imx8m-voipac-peripheral-test.sh -basic sda1 sdb1 mmcblk1p1 | tee -i imx8m-emc-testing.log

Testing scripts

Peripherals heavy testing script

This code was used during the measurements, focusing on peripherals influence on the emissions. The complete script can also be found in the downloads section.

#!/bin/sh
 
# iMX8M Industrial Development Kit peripheral test
  
mountDevice() {
  mkdir -p "/media/$2"
  mount /dev/$1 /media/$2
  cat /proc/mounts | grep -F "/dev/$1 /media/$2"
  if [ "$?" -eq "0" ]; then
    echo "$2 mounted"
  else
    echo "$2 not mounted"; exit 2
  fi
}
 
# prepare files
cd ~/
mkdir -p imx8m-industrial-testing/
cd imx8m-industrial-testing/
   
touch imx8m-industrial-testing.log
touch cpu-temp.log
 
basic=0
pro=0
max=0
case $1 in
  -basic)  basic=1 ;;
  -pro)  pro=1 ;;
  -max)  max=1 ;;
  *)
esac
  
# mount devices
mountDevice $2 usb0
mountDevice $3 usb1
mountDevice $4 mmc0
 
updateLogFiles() {
  # obtain board ID from IP address - be sure addresses are allocated based on MAC
  boardID=$(/sbin/ip -o -4 addr list eth0 | awk '{print $4}' | cut -d/ -f1 | cut -d'.' -f4 | cut -d'2' -f2);
  # be sure time server is running on DHCP server
  currentTime=`date +%Y-%m-%d.%H:%M`
   
  mv imx8m-industrial-testing.log imx8m-industrial-$boardID-testing.log.$currentTime
  mv cpu-temp.log imx8m-industrial-$boardID-cpu-temp.log.$currentTime
}
 
finish_test_now() {
  echo "$(date +\%Y/\%m/\%d-\%T)($(date +\%Z)) Ctrl+C Detected: End of the test"
  precced=0;
  #kill -INT $vid_pid $str_pid $log_pid;
  sleep 3;
  test_status=`cat imx8m-industrial-testing.log | grep -i "error" | grep -v -e "0 errors" -e "no corrected errors"`
  if [ -z "$test_status" ]
  then
    echo "*********TEST PASS*********"
  else
    echo "*********TEST FAIL*********"
    echo "List of detected errors:"
    cat imx8m-industrial-testing.log | grep -i "error" | grep -v -e "0 errors" -e "no corrected errors" -e "List of detected errors:"
  fi
  updateLogFiles
  exit;
}
  
# kill all processes if Ctrl+C is detected
trap finish_test_now 2
 
# play video stream
gst-launch-1.0 -q imxv4l2src ! autovideosink &
 
# stressapptest - CPU threads and RAM memory threads
if [ "${basic}" -eq "1" ]; then
  stress-ng --cpu 2 --vm 4 &
  str_pid=$!
fi
if [ "${pro}" -eq "1" ]; then
  stress-ng --cpu 4 --vm 4 &
  str_pid=$!
fi
if [ "${max}" -eq "1" ]; then
  stress-ng --cpu 4 --vm 4 &
  str_pid=$!
fi
echo "$(date +\%Y/\%m/\%d-\%T)($(date +\%Z)) Starting stressapptest with PID: " $str_pid
  
proceed=1
# create test files
file1_path=`mktemp`
file2_path=`mktemp`
file1=`basename $file1_path`
file2=`basename $file2_path`

dd if=/dev/urandom of=$file1_path bs=1024 count=10000
dd if=/dev/urandom of=$file2_path bs=1024 count=10000
 
cp1_from="/media/mmc0/"
cp1_to="/media/usb0/"
 
cp2_from="/media/usb0/"
cp2_to="/media/usb1/"
 
#copy files in case they are missing
cp $file1_path $cp1_from
cp $file1_path $cp1_to
cp $file2_path $cp2_from
cp $file2_path $cp2_to
  
while [ $proceed -eq 1 ]
do
  # before running script check if the ip address exist 
  ping -q -c1 192.168.0.2 >> imx8m-industrial-testing.log
  if [ $? -ne 0 ]
  then
    echo "$(date +\%Y/\%m/\%d-\%T)($(date +\%Z)) ERROR: Ping failed"
  else
    echo "$(date +\%Y/\%m/\%d-\%T)($(date +\%Z)) Ping OK"
  fi
  
  cp1_done=`ps | grep $cp1_pid | grep cp`
  if [ -z "$cp1_done" ]; then # copy finished
    if cmp -s $cp1_from$file1 $cp1_to$file1; then
      echo "$(date +\%Y/\%m/\%d-\%T)($(date +\%Z)) PASS: Copying file from $cp1_from to $cp1_to successful"
    else
      echo "$(date +\%Y/\%m/\%d-\%T)($(date +\%Z)) ERROR: Difference between files on $cp1_from and $cp1_to detected"
    fi
    cp1_temp=$cp1_from # swap destinations
    cp1_from=$cp1_to
    cp1_to=$cp1_temp
      
    rm $cp1_to$file1 # remove destination file
      
    cp $cp1_from$file1 $cp1_to$file1 &
    cp1_pid=$!
    echo "$(date +\%Y/\%m/\%d-\%T)($(date +\%Z)) Started copying file from $cp1_from to $cp1_to"
  fi
    
  cp2_done=`ps | grep $cp2_pid | grep cp`
  if [ -z "$cp2_done" ]; then # copy finished
    if cmp -s $cp2_from$file2 $cp2_to$file2; then
      echo "$(date +\%Y/\%m/\%d-\%T)($(date +\%Z)) PASS: Copying file from $cp2_from to $cp2_to successful"
    else
      echo "$(date +\%Y/\%m/\%d-\%T)($(date +\%Z)) ERROR: Difference between files on $cp2_from and $cp2_to detected"
    fi
    cp2_temp=$cp2_from # swap destinations
    cp2_from=$cp2_to
    cp2_to=$cp2_temp
      
    rm $cp2_to$file2 # remove destination file
      
    cp $cp2_from$file2 $cp2_to$file2 &
    cp2_pid=$!
    echo "$(date +\%Y/\%m/\%d-\%T)($(date +\%Z)) Started copying file from $cp2_from to $cp2_to"
  fi
  
done

Module heavy testing script

This script was utilised for testing procedure where the measurement was primarily focused on the module emissions. To use this script, plug the development kit into mains, connect it to controlling PC via console and copy the code below:

for d in $(seq 1 1 999)
do
	uptime
	echo "Test $a Test $b Test $c  $d times"
	echo "Start stress-ng --iomix 1 -t 10 -v"
	stress-ng --iomix 1 -t 10 -v
	echo "End"
	echo "Start Thermal zone information"
	stress-ng --matrix 0 --tz -t 10 --log-brief -t 10
	echo "End"
	ping -q -c1 192.168.0.2 >> imx8m-industrial-testing.log
	  if [ $? -ne 0 ]
	  then
		echo "$(date +\%Y/\%m/\%d-\%T)($(date +\%Z)) ERROR: Ping failed"
	  fi
	echo "End"
done

Starting camera capture

To initiate the Digilent camera to start the recording of video stream, following command can be used:

GST_DEBUG=GST_BUFFER:5 gst-launch-1.0 v4l2src device=/dev/video1 ! 'video/x-raw,framerate=30/1' ! autovideosink