Review and Setup of the A7670E LTE Modem on Linux


Features:

  • Connectivity: GSM/GPRS/EDGE: 900/1800 MHz and LTE-FDD: B1, B3, B5, B7, B8, B20.

  • Navigation: Includes an input for a GNSS antenna for satellite positioning.

  • Data Rates: Over LTE — Downlink up to 10 Mbps, Uplink up to 5 Mbps. Over EDGE: up to 236.8 Kbps in both directions.

  • Power Supply: 3.4 V to 4.2 V — perfectly matching the operating voltage range of Li-Ion batteries.

  • Interfaces: USB — the module emulates a network card (RNDIS) and UART. There is also a separate, “real” UART. However, it lacks an analog audio interface for sound and a microphone.

  • Card Slot: A standard, convenient NanoSIM slot is soldered onto the board.

In addition to the micro-USB connector, the board features a standard 7-pin header. Here is their pinout:

Letter Function
G Ground (GND)
R UART RX
T UART TX
K Module power control (Power Key)
V Power (VCC)
G Ground (GND)
S Sleep — this pin can be used to put the modem into deep sleep mode for minimal power consumption

After connecting it, a bunch of new interfaces appeared in dmesg:

[ 5049.440788] usb 3-1.2: new high-speed USB device number 6 using xhci_hcd
[ 5049.554266] usb 3-1.2: New USB device found, idVendor=2ecc, idProduct=3004, bcdDevice= 0.00
[ 5049.554281] usb 3-1.2: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[ 5049.554287] usb 3-1.2: Product: Arom Usb Boot Port
[ 5049.554293] usb 3-1.2: Manufacturer: ASR Microelectronics
[ 5049.554298] usb 3-1.2: SerialNumber: arom0123456789
[ 5049.658700] cdc_acm 3-1.2:1.0: ttyACM0: USB ACM device
[ 5049.658725] usbcore: registered new interface driver cdc_acm
[ 5049.658727] cdc_acm: USB Abstract Control Model driver for USB modems and ISDN adapters
[ 5049.758004] usb 3-1.2: USB disconnect, device number 6
[ 5052.523797] usb 3-1.2: new high-speed USB device number 7 using xhci_hcd
[ 5052.625945] usb 3-1.2: New USB device found, idVendor=1e0e, idProduct=9011, bcdDevice= 1.00
[ 5052.625956] usb 3-1.2: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[ 5052.625959] usb 3-1.2: Product: A76XX Series LTE Module
[ 5052.625963] usb 3-1.2: Manufacturer: SIMCom Wireless Solution
[ 5052.625965] usb 3-1.2: SerialNumber: 
[ 5052.839599] rndis_host 3-1.2:1.0 usb0: register 'rndis_host' at usb-0000:04:00.4-1.2, RNDIS device, ae:0c:29:a3:9b:6d
[ 5052.839647] usbcore: registered new interface driver rndis_host
[ 5052.839989] usbcore: registered new interface driver option
[ 5052.840009] usbserial: USB Serial support registered for GSM modem (1-port)
[ 5052.840304] option 3-1.2:1.2: GSM modem (1-port) converter detected
[ 5052.840376] usb 3-1.2: GSM modem (1-port) converter now attached to ttyUSB0
[ 5052.840430] option 3-1.2:1.4: GSM modem (1-port) converter detected
[ 5052.840495] usb 3-1.2: GSM modem (1-port) converter now attached to ttyUSB1
[ 5052.840561] option 3-1.2:1.5: GSM modem (1-port) converter detected
[ 5052.840864] usb 3-1.2: GSM modem (1-port) converter now attached to ttyUSB2
[ 5052.840961] option 3-1.2:1.3: GSM modem (1-port) converter detected
[ 5052.841061] usb 3-1.2: GSM modem (1-port) converter now attached to ttyUSB3
[ 5052.892029] rndis_host 3-1.2:1.0 enp4s0f4u1u2: renamed from usb0

A new network interface also appeared in the system:

$ip a
...
12: enp4s0f4u1u2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UNKNOWN group default qlen 1000
    link/ether ae:0c:29:a3:9b:6d brd ff:ff:ff:ff:ff:ff
    altname enxae0c29a39b6d
    inet 192.168.0.100/24 brd 192.168.0.255 scope global dynamic noprefixroute enp4s0f4u1u2
       valid_lft 86114sec preferred_lft 86114sec
    inet6 fe80::342f:34cc:ea27:3082/64 scope link noprefixroute 
       valid_lft forever preferred_lft forever

To test it, I ran ping 192.168.0.1 — I got a reply, which means IP communication with the modem is established. However, ping 8.8.8.8 returned nothing.

I tried opening the web interface in a browser at http://192.168.0.1/, hoping to see a control panel, but no luck. Judging by the nmap scan results, the only service running on the modem is a DNS resolver:

$ nmap 192.168.0.1
Starting Nmap 7.99 ( https://nmap.org ) at 2026-06-20 14:54 +0300
Nmap scan report for 192.168.0.1
Host is up (0.0072s latency).
Not shown: 999 closed tcp ports (conn-refused)
PORT   STATE    SERVICE
53/tcp filtered domain

Alright, in that case, let’s connect to the UART console and check the device status via AT commands. The modem creates 4 virtual COM ports in the system:

$ ls -l /dev/ttyACM* /dev/ttyUSB*
crw-rw----+ 1 root uucp 188, 0 Jun 20 14:43  /dev/ttyUSB0
crw-rw----+ 1 root uucp 188, 1 Jun 20 14:43  /dev/ttyUSB1
crw-rw----+ 1 root uucp 188, 2 Jun 20 14:43  /dev/ttyUSB2
crw-rw----+ 1 root uucp 188, 3 Jun 20 14:43  /dev/ttyUSB3

Ports /dev/ttyUSB0 and /dev/ttyUSB1 didn’t respond to AT commands, but I managed to start a dialogue through /dev/ttyUSB2:

$ screen /dev/ttyUSB2 115200

AT
OK
AT+CPIN?
+CPIN: READY

No PIN code is required for activation, the SIM card is active. Let’s check the network registration status:

AT+COPS?
+COPS: 0,2,"25501",7

Everything is great here: we are on the Vodafone Ukraine network (25501) and connected specifically via LTE (7). Now let’s look at the detailed base station information:

AT+CPSI?
+CPSI: LTE,Online,255-01,0xXXXX,XXXXXXXXX,XX,EUTRAN-BAND8,3676,2,2,11,63,62,3

The modem is working correctly. Since I am deep inside a building, the device is only catching the long-range, penetrating 900 MHz signal (EUTRAN-BAND8).

So, on the physical layer, everything is working — the card is recognized, and the connection to the base station is stable. Yet, there is still no internet access on the Linux. Let’s check the APN settings:

AT+CGDCONT?
+CGDCONT: 1,"IP","internet.MNC001.MCC255.GPRS","10.105.2.225",0,0,,,,

The modem successfully obtained the profile configuration from the carrier automatically. Let’s verify if there is internet access on the module itself by running a ping via an AT command:

AT+CPING="8.8.8.8",1,4
OK

+CPING: 1,8.8.8.8,92,310,114
+CPING: 1,8.8.8.8,92,60,114
+CPING: 1,8.8.8.8,92,60,114
+CPING: 1,8.8.8.8,92,50,114
+CPING: 3,4,4,0,50,310,86

That works too? What a wonderful day! Everything works everywhere, but I’m not getting the internet :) After searching for some information, I found out that I should try switching the modem from router mode to transparent Bridge mode:

AT+DIALMODE=0
OK
AT+RESET

The switch was successful. After this, the module restarts, and all USB devices momentarily disappear from the system. Just in case, I also restarted the system’s NetworkManager:

sudo systemctl restart NetworkManager

After these tweaks, the network interfaces didn’t visually change (it’s still the same 192.168.0.100 subnet), but the result was different:

$ ping 8.8.8.8
PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.
64 bytes from 8.8.8.8: icmp_seq=1 ttl=115 time=42.8 ms
64 bytes from 8.8.8.8: icmp_seq=2 ttl=115 time=269 ms
64 bytes from 8.8.8.8: icmp_seq=3 ttl=115 time=246 ms

Pings finally started going through on the PC. Finally, I checked the data transfer speed this module can provide.

Test 1: Modem on the desk deep inside the room

Speedtest in the browser gives quite unstable results:

 



Testing via iperf3 showed the following numbers:

$ iperf3 -c red -R
Connecting to host red, port 5201
Reverse mode, remote host red is sending
[  5] local 192.168.0.100 port 53722 connected to XXX.XX.XXX.XX port 5201
[ ID] Interval           Transfer     Bitrate
[  5]   0.00-1.00   sec  0.00 Bytes  0.00 bits/sec                  
[  5]   1.00-2.00   sec   256 KBytes  2.10 Mbits/sec                  
[  5]   2.00-3.00   sec   256 KBytes  2.10 Mbits/sec                  
[  5]   3.00-4.00   sec   128 KBytes  1.05 Mbits/sec                  
[  5]   4.00-5.00   sec   128 KBytes  1.05 Mbits/sec                  
[  5]   5.00-6.00   sec   128 KBytes  1.05 Mbits/sec                  
[  5]   6.00-7.00   sec   256 KBytes  2.10 Mbits/sec                  
[  5]   7.00-8.00   sec   256 KBytes  2.10 Mbits/sec                  
[  5]   8.00-9.00   sec   256 KBytes  2.10 Mbits/sec                  
[  5]   9.00-10.00  sec   128 KBytes  1.05 Mbits/sec                  
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate         Retr
[  5]   0.00-10.04  sec  1.98 MBytes  1.66 Mbits/sec    2            sender
[  5]   0.00-10.00  sec  1.75 MBytes  1.47 Mbits/sec                  receiver

Upload test:

$ iperf3 -c red 
Connecting to host red, port 5201
[  5] local 192.168.0.100 port 54704 connected to XXX.XX.XXX.XX port 5201
[ ID] Interval           Transfer     Bitrate         Retr  Cwnd
[  5]   0.00-1.00   sec   128 KBytes  1.05 Mbits/sec    0   40.7 KBytes       
[  5]   1.00-2.00   sec   128 KBytes  1.05 Mbits/sec    0   47.4 KBytes       
[  5]   2.00-3.00   sec   128 KBytes  1.05 Mbits/sec    0   54.2 KBytes       
[  5]   3.00-4.00   sec   256 KBytes  2.10 Mbits/sec    3   42.0 KBytes       
[  5]   4.00-5.00   sec   128 KBytes  1.05 Mbits/sec    0   52.9 KBytes       
[  5]   5.00-6.00   sec  0.00 Bytes  0.00 bits/sec    2   39.3 KBytes       
[  5]   6.00-7.00   sec   128 KBytes  1.05 Mbits/sec    0   42.0 KBytes       
[  5]   7.00-8.00   sec   128 KBytes  1.05 Mbits/sec    0   44.7 KBytes       
[  5]   8.00-9.00   sec  0.00 Bytes  0.00 bits/sec    0   46.1 KBytes       
[  5]   9.00-10.00  sec  0.00 Bytes  0.00 bits/sec    0   47.4 KBytes       
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate         Retr
[  5]   0.00-10.00  sec  1.00 MBytes   839 Kbits/sec    5            sender
[  5]   0.00-10.96  sec  1.00 MBytes   765 Kbits/sec                  receiver

Due to the weak signal level inside the room, the speed is low, with packet loss and retransmissions (Retr).

Test 2: Modem raised higher, antenna pointed towards the window

Speedtest shows a different picture now:

And iperf3 also showed a noticeable improvement in results:

$ iperf3 -c red -R
Connecting to host red, port 5201
Reverse mode, remote host red is sending
[  5] local 192.168.0.100 port 59852 connected to XXX.XX.XXX.XX port 5201
[ ID] Interval           Transfer     Bitrate
[  5]   0.00-1.00   sec   512 KBytes  4.19 Mbits/sec                  
[  5]   1.00-2.00   sec   384 KBytes  3.15 Mbits/sec                  
[  5]   2.00-3.00   sec   384 KBytes  3.15 Mbits/sec                  
[  5]   3.00-4.00   sec   384 KBytes  3.15 Mbits/sec                  
[  5]   4.00-5.00   sec   640 KBytes  5.25 Mbits/sec                  
[  5]   5.00-6.00   sec   640 KBytes  5.24 Mbits/sec                  
[  5]   6.00-7.00   sec   768 KBytes  6.30 Mbits/sec                  
[  5]   7.00-8.00   sec   640 KBytes  5.24 Mbits/sec                  
[  5]   8.00-9.00   sec   640 KBytes  5.24 Mbits/sec                  
[  5]   9.00-10.00  sec   512 KBytes  4.20 Mbits/sec                  
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate         Retr
[  5]   0.00-10.04  sec  5.56 MBytes  4.65 Mbits/sec    0            sender
[  5]   0.00-10.00  sec  5.38 MBytes  4.51 Mbits/sec                  receiver

Upload test:

$ iperf3 -c red
Connecting to host red, port 5201
[  5] local 192.168.0.100 port 59606 connected to XXX.XX.XXX.XX port 5201
[ ID] Interval           Transfer     Bitrate         Retr  Cwnd
[  5]   0.00-1.00   sec   512 KBytes  4.19 Mbits/sec    3   35.2 KBytes       
[  5]   1.00-2.00   sec   384 KBytes  3.14 Mbits/sec    0   46.1 KBytes       
[  5]   2.00-3.00   sec   384 KBytes  3.15 Mbits/sec    2   39.3 KBytes       
[  5]   3.00-4.00   sec   512 KBytes  4.20 Mbits/sec    1   31.2 KBytes       
[  5]   4.00-5.00   sec   256 KBytes  2.10 Mbits/sec    0   43.4 KBytes       
[  5]   5.00-6.00   sec   512 KBytes  4.20 Mbits/sec    0   46.1 KBytes       
[  5]   6.00-7.00   sec   384 KBytes  3.14 Mbits/sec    2   40.7 KBytes       
[  5]   7.00-8.00   sec   256 KBytes  2.10 Mbits/sec    0   46.1 KBytes       
[  5]   8.00-9.00   sec   512 KBytes  4.20 Mbits/sec    1   39.3 KBytes       
[  5]   9.00-10.00  sec   384 KBytes  3.14 Mbits/sec    0   44.7 KBytes       
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate         Retr
[  5]   0.00-10.00  sec  4.00 MBytes  3.35 Mbits/sec    9            sender
[  5]   0.00-10.13  sec  4.00 MBytes  3.31 Mbits/sec                  receiver

Conclusions

The A7670E is an interesting, stable, and quite affordable LTE Cat 1 module. You shouldn’t expect the maximum speeds of modern mobile internet from it, but for telemetry tasks, M2M, remote control, or collecting data from sensors, its bandwidth is more than enough.

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