Cellular modems on i.MX8 boards, Nitrogen8M and Nitrogen8M Mini under Ubuntu

Published on September 23, 2019

Table of Contents

  1. For the impatient
  2. Programming the image
  3. Contents
  4. Hardware Installation
    1. Installing EC25 modem on Nitrogen8M and Nitrogen8M Mini
  5. Using modem on a headless (No GUI) Ubuntu system
    1. Software prerequisites
    2. Testing whether the system recognizes the modem
    3. Finding the optimal antenna position
    4. Checking the subscriber information
    5. Connecting to the internet
Nitrogen8M Plus SMARCNitrogen8M Mini SMARCNitrogen8M Plus SOMNitrogen8M Mini SBCNitrogen8M Nano SOMNitrogen8M Mini SOMNitrogen8M SOMNitrogen8M SBC

In this post, we'll walk through all of the steps needed to configure a specific set of modems under Ubuntu as a reference. We'll use Quectel EC25 modem in this showcase, if you're using another modem or another userspace, the details may be different, but the fundamentals will be the same. We used and tested the Quectel EC25 Mini PCIe , and ublox SARA-R410M-02B during this process, and will be adding them to our default kernels going forward. As you can see in this file here, and here, the following Qualcomm/Quectel models are supported in the current kernel :

  • UC15  UMTS/HSDPA : 3.6 Mbit/s DL,  384 Kbit/s UL
  • UC20  UMTS/HSPA+ : 14.4 Mbit/s DL,  5.76 Mbit/s UL
  • EC21   LTE Cat1 : 10 Mbit/s DL,  5 Mbit/s UL
  • EC25   LTE Cat4 : 150 Mbit/s DL,  50 Mbit/s UL
  • BG96  LTE Cat M1/NB1 : 375 kbit/s DL and 375 kbit/s UL
  • EP06   LTE Cat6 : 300 Mbit/s DL,  50 Mbit/s UL

And from u-blox:

  • SARA-R410M-02B LTE Cat M1/NB1 : 300 kbit/s DL and 375 kbit/s UL
  • SARA-R410M-52B LTE Cat M1 : 300 kbit/s DL and 375 kbit/s UL

For the impatient

These images contain Freescale-licensed content, so you will need to register on our web-site and log in before you can accept the license agreement and download the images from here:

Update#1:

Update#2:

The above images contain all packages what needed to work with cellular modems, including network-manager and modemmanager and screen packages.

Programming the image

Since the Nitrogen8M_Mini board has an SD card slot, not like Nitrogen8M, you can create an SD card similarly to i.MX6 boards. The image is a slightly-less-than-8GiB image file containing the partition table.  For example, if you want to create an SD card for a console image, you need to do the following : 

$ sudo apt install gddrescue xz-utils util-linux
$ gunzip 20200408-nitrogen8mm-4.14.x_2.0.1_ga-bionic-en_US-console-weston_aarch64.img.gz
$ sudo ddrescue -D --force 20200408-nitrogen8mm-4.14.x_2.0.1_ga-bionic-en_US-console-weston_aarch64.img /dev/sdX

You have to replace sdX with your actual SDHC reader/writer device. Use the lsblk command to check it. Type lsblk with unplugged SDHC reader, then insert the device, and type lsblk again. A new node will be added , that is your SDHC reader/writer device.

Contents

In the rest of this post we'll walk through the following:

Hardware Installation

Installing EC25 modem on Nitrogen8M and Nitrogen8M Mini

These boards require a mini PCI-e to USB adapter to connect the EC25 mini PCIe modem. They're cheap and easy to find (Search Amazon for "mini PCI-e USB wireless SIM" keywords). Th uBlox SARA modem doesn't need adapter, it has a built-in micro USB connector or its a surface mounted unit on your board. If you need a free USB port, install a USB HUB, and problem solved.

   

EC25-A (American version)

   

EC25-E (European version) Modem in USB adapter

   

uBlox SARA-R410M

Using modem on a headless (No GUI) Ubuntu system

Software prerequisites

Make sure you have the latest kernel installed, but at least the ABI >= 17 : 

ubuntu@bionic-dev64:/$ uname -r
4.14.98-17-boundary-17b

If this is not the case, please update your system : 

ubuntu@bionic-dev64:/$ aptu

We will solve the modem handling tasks with the modemmanager package. This package provides a unified high level API for communicating with (mobile broadband) modems. ModemManager is a daemon that gets started at boot time. The modemmanager package provides a command line tool, named mmcli, to control the ModemManager daemon. That will be the tool used below. We will solve the connection handling tasks with the network-manager package. We can use the NetworkManager's huge database to use the cellular service provider data and settings. With the NetworkManager we can create connection configuration files, with specific parameters, that makes internet connection handling very easy. Make sure you have installed modemmanager , networkmanager packages : 

ubuntu@bionic-dev64:~$ dpkg -l | grep -e modemmanager -e network-manager
ii  modemmanager        1.10.0-1~ubuntu18.04.2    arm64    D-Bus service for managing modems
ii  network-manager     1.10.6-2ubuntu1.1         arm64    network management framework (daemon and userspace tools)

If these packages are not installed, please type the following and then restart the system: 

ubuntu@bionic-dev64:/$ sudo apt install modemmanager network-manager uuid

If everything went well, your ModemManager and NetworkManager will start at boot time. You can check it like so: 

ubuntu@bionic-dev64:~$ systemctl --no-pager list-units --state=running | grep Manager.service
ModemManager.service            loaded active running Modem Manager
NetworkManager.service          loaded active running Network Manager

When ModemManager starts it scans the serial ports for modems and it tries to recognize them. It takes few seconds after the login prompt, so you'll need to be patient. Depending on your modem it might be necessary to create the following zero length file (to set your modem managed): 

ubuntu@bionic-dev64:~$ sudo touch /etc/NetworkManager/conf.d/10-globally-managed-devices.conf

Testing whether the system recognizes the modem

You can check the presence of the USB modem device using lsusb: 

ubuntu@bionic-dev64:~$ lsusb
Bus 003 Device 002: ID 152d:0578 JMicron Technology Corp. / JMicron USA Technology Corp. JMS567 SATA 6Gb/s bridge
Bus 003 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 001 Device 007: ID 0458:018b KYE Systems Corp. (Mouse Systems) 
Bus 001 Device 006: ID 04d9:a0f8 Holtek Semiconductor, Inc. 
Bus 001 Device 005: ID 2c7c:0125 Quectel Wireless Solutions Co., Ltd. EC25 LTE modem
Bus 001 Device 002: ID 05e3:0608 Genesys Logic, Inc. Hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

The 6th one with 2c7c:0125 key, that is our EC25 modem. You can check the modem's serial ports : 

ubuntu@bionic-dev64:~$ ls -a1 /dev/ttyU*
/dev/ttyUSB0
/dev/ttyUSB1
/dev/ttyUSB2
/dev/ttyUSB3

The EC25 modem creates three USB serial ports (ttyUSB1 does not belong to the modem in the above list). Other modems may create fewer or more. At this point, you can see if modemmanager detects the modem with mmcli -L: 

ubuntu@bionic-dev64:~$ mmcli -L
	/org/freedesktop/ModemManager1/Modem/0 [QUALCOMM INCORPORATED] QUECTEL Mobile Broadband Module

And you can see more details of the modem with mmcli -m: 

ubuntu@bionic-dev64:~$ mmcli -m 0
  --------------------------------
  General  |            dbus path: /org/freedesktop/ModemManager1/Modem/0
		   |            device id: 94ec3702b44ee6fb7d67141906997d7070bf8198
  --------------------------------
  Hardware |         manufacturer: QUALCOMM INCORPORATED
		   |                model: QUECTEL Mobile Broadband Module
		   |             revision: EC25EFAR06A04M4G
		   |         h/w revision: 10000
		   |            supported: gsm-umts, lte
		   |              current: gsm-umts, lte
		   |         equipment id: 866758045611098
  --------------------------------
  System   |               device: /sys/devices/platform/32e50000.usb/ci_hdrc.1/usb1/1-1/1-1.2/1-1.2.1
		   |              drivers: option1, qmi_wwan
		   |               plugin: Quectel
		   |         primary port: cdc-wdm0
		   |                ports: ttyUSB0 (qcdm), ttyUSB2 (at), cdc-wdm0 (qmi), wwan0 (net), 
		   |                       ttyUSB3 (at)
  --------------------------------
  Status   |                 lock: sim-pin2
		   |       unlock retries: sim-pin (3), sim-pin2 (3), sim-puk (10), sim-puk2 (10)
		   |                state: registered
		   |          power state: on
		   |          access tech: lte
		   |       signal quality: 84% (recent)
  --------------------------------
  Modes    |            supported: allowed: 2g; preferred: none
		   |                       allowed: 3g; preferred: none
		   |                       allowed: 4g; preferred: none
		   |                       allowed: 2g, 3g; preferred: 3g
		   |                       allowed: 2g, 3g; preferred: 2g
		   |                       allowed: 2g, 4g; preferred: 4g
		   |                       allowed: 2g, 4g; preferred: 2g
		   |                       allowed: 3g, 4g; preferred: 3g
		   |                       allowed: 3g, 4g; preferred: 4g
		   |                       allowed: 2g, 3g, 4g; preferred: 4g
		   |                       allowed: 2g, 3g, 4g; preferred: 3g
		   |                       allowed: 2g, 3g, 4g; preferred: 2g
		   |              current: allowed: 2g, 3g, 4g; preferred: 4g
  --------------------------------
  Bands    |            supported: egsm, dcs, utran-1, utran-5, utran-8, eutran-1, eutran-3, 
		   |                       eutran-5, eutran-7, eutran-8, eutran-20, eutran-38, eutran-40, 
		   |                       eutran-41
		   |              current: egsm, dcs, utran-1, utran-5, utran-8, eutran-1, eutran-3, 
		   |                       eutran-5, eutran-7, eutran-8, eutran-20, eutran-38, eutran-40, 
		   |                       eutran-41
  --------------------------------
  IP       |            supported: ipv4, ipv6, ipv4v6
  --------------------------------
  3GPP     |                 imei: 866758045611098
		   |          operator id: unknown
		   |         registration: unknown
  --------------------------------
  3GPP EPS | ue mode of operation: ps-2
  --------------------------------
  SIM      |            dbus path: /org/freedesktop/ModemManager1/SIM/0
ubuntu@bionic-dev64:~$ nmcli dev
DEVICE    TYPE        STATE         CONNECTION 
eth0       ethernet   connected     Wired connection 1 
cdc-wdm0   gsm        disconnected  -- 
wlan0      wifi       disconnected  -- 
lo         loopback   unmanaged     --

Finding the optimal antenna position

Now we have to stop NetworkManager and ModemManager temporarily, because we want to run some more tests: 

ubuntu@bionic-dev64:~$ systemctl --no-pager list-units --state=running | grep Manager.service
ModemManager.service            loaded active running Modem Manager                  
NetworkManager.service          loaded active running Network Manager                
ubuntu@bionic-dev64:~$ sudo systemctl stop ModemManager.service NetworkManager.service
ubuntu@bionic-dev64:~$ systemctl --no-pager list-units --state=running | grep Manager.service
ubuntu@bionic-dev64:~$

And we start screen serial console application to communicate with modem on ttyUSB2 (primary AT port of the modem, as shown above). 

ubuntu@bionic-dev64:~$ screen /dev/ttyUSB2 115200

Now you get an empty console screen. If local echo is not set, then type ATZ for the modem blindly, and that will reset it. Now type : ATI Quectel EC25 Revision: EC25EFAR06A04M4G OK This tells us that the modem is present and working. Now type the following command, to check if your GSM antenna is set properly: AT+CSQ +CSQ: 26,99 OK This is the GSM signal quality in +CSQ: RSSI, BER format, where RSSI = Received Signal Strength Indication, and BER = Channel Bit Error Rate 0...7  (in percent) or 99 = Not known or not detectable The RSSI = 99 (+CSQ: 99,99) means an unknown or undetectable signal level. Here is a table to calculate the signal levels from RSSI :

Calculating signal levels from RSSI to dBm
RSSI 0 1 2 3 4 5 6 7
level dBm -113 dBm -111 dBm -109 dBm -107 dBm -105 dBm -103 dBm -101 dBm - 99 dBm
RSSI 8 9 10 11 12 13 14 15
level dBm -97 dBm -95 dBm -93 dBm -91 dBm -89 dBm -87 dBm -85 dBm -83 dBm
RSSI 16 17 18 19 20 21 22 23
level dBm -81 dBm -79 dBm -77 dBm -75 dBm -73 dBm -71 dBm -69 dBm -67 dBm
RSSI 24 25 26 27 28 29 30 31
level dBm -65 dBm -63 dBm -61 dBm -59 dBm -57 dBm -55 dBm -53 dBm >-51 dBm

Move/rotate your antenna and repeat the command above until you find the antenna's optimal position. In general we can say:

  • RSSI values below 10 will not work
  • RSSI values between 10 and 15 will have many disconnections
  • RSSI values between 15 and 20 are weak, but could work
  • RSSI values between 20 and 25 are good
  • RSSI values above 25 are excellent, recommended

For LTE 100 Mbit/s or higher speed connections you'll need excellent signal quality, RSSI > 25 for reliable service.

Checking the subscriber information

You should check your SIM card, since it provides a lot of information: AT+CIMI 3100262475092493 OK This command will query your SIM card's IMSI number ( International Mobile Subscriber Identity ) The first 3 digits of IMSI number is MCC ( Mobile Country Code ) The following 2 (Europe) or 3 (North America) digits of the IMSI is the MNC ( Mobile Network Code ) The remaining digits is the MIN ( Mobile Identification Number ) You can check your MCC/MNC code in the following page : Mobile Country Codes For example if your MCC is 310 and your MNC is 026 then you are a T-Mobile subscriber in USA . Why is this important ? Because on this page : Mobile Broadband Service Providers You can find your APN number based on you MCC and MNC number, and that is necessary, when you want to create a connection setup,  to dial up your service provider. Of course you may ask your service provider about these datas. If you get an error : AT+CIMI +CME ERROR: Sim failure Then your SIM card is not inserted properly, or it is locked by the CardLock feature, or its broken. If the tests above pass, you can exit the screen console application ( Q, then Y ) .

Connecting to the internet

For doing that, you have to create a connection setup file as user "root" in the /etc/NetworkManager/system-connections directory, with the following content : 

ubuntu@bionic-dev64:/$ sudo cat /etc/NetworkManager/system-connections/MyModem
[connection]
id=EC25
uuid=15d742f1-2b5a-421e-9f27-fcb1fc26d72d
type=gsm
autoconnect=false

[ipv4]
method=auto

[gsm]
number=*99#
#username=user
#password=passwd
apn=epc.tmobile.com
[serial]
baud=115200

The username and the password  are usually not necessary, or can be anything. The uuid is a unique identifier you can create with the uuid command (which installed earlier) : 

ubuntu@bionic-dev64:~$ uuid
15d742f1-2b5a-421e-9f27-fcb1fc26d72d
ubuntu@bionic-dev64:~$

The id can be anything that you can memorize easily ("EC25" is not mandatory). The same goes to for the file name "MyModem". It can be anything. You have to get the apn from your service provider, or from HERE , as described above, earlier. This is a minimal connection setup file. For detailed instructions, type : 

ubuntu@bionic-dev64:/$ man nm-settings

When finished, set the connection setup file's attribute to 0600 : 

ubuntu@bionic-dev64:/$ sudo chmod 600 /etc/NetworkManager/system-connections/MyModem

And make sure that the file's owner:group is root. If the owner is not root, then the Network Manager will ignore the connection setup. 

ubuntu@bionic-dev64:/$ sudo chown root:root /etc/NetworkManager/system-connections/MyModem

Now reboot, and wait for modemmanager to recognize the modem. Then enable modem : 

ubuntu@bionic-dev64:/$ sudo mmcli -m 0 -e
successfully enabled the modem
ubuntu@bionic-dev64:/$

And check the connections : 

ubuntu@bionic-dev64:~$ nmcli con
NAME                UUID                                  TYPE      DEVICE 
Wired connection 1  355a9384-3ebf-3a20-b822-e3f4b39b4b46  ethernet  eth0   
EC25                15d742f1-2b5a-421e-9f27-fcb1fc26d72d  gsm       --

Then you can dial (connect) to any of them : 

ubuntu@bionic-dev64:~$ sudo nmcli con up id EC25
Connection successfully activated (D-Bus active path: /org/freedesktop/NetworkManager/ActiveConnection/2)
ubuntu@bionic-dev64:/$

You can see the status of the active connections like this : 

ubuntu@bionic-dev64:~$ nmcli con show --active
NAME                UUID                                  TYPE      DEVICE   
EC25                15d742f1-2b5a-421e-9f27-fcb1fc26d72d  gsm       cdc-wdm0 
Wired connection 1  355a9384-3ebf-3a20-b822-e3f4b39b4b46  ethernet  eth0

You can use the internet now, download, upload, browse, launch wget, as you like it. When finished, you can disconnect with the following command. You don't need to be in a hurry, service providers usually bill for data traffic and not connection time. 

ubuntu@bionic-dev64:~$ sudo nmcli con down id EC25
Connection 'EC25' successfully deactivated (D-Bus active path: /org/freedesktop/NetworkManager/ActiveConnection/2)

Pay close attention to the commands above, since we show both mmcli (modem manager) and nmcli (network manager). A note: when you restart the system, Network Manager needs about 20 seconds to close and release the network devices. ("A stop job is running for Modem Manager") Please be patient, the proper shutdown is important as always. As always please tell us how this works for you. Contact us if you have any trouble or ask a question by posting a reply below.