Modems

This is a knowledge base for supported modems. Documentation is sparse at times, so we have collected relevant information here in one place.

Zero-4G-CAT1-Hub¶

This is the modem most widely available on AliExpress, sold under different names by different vendors. The actual OEM appears to be Mcuzone. It comes in four distinct versions, usually labeled on top of the MCU:

Model	Bands	GPS	Speed
CAT1/LTE	1, 3, 5, 8, 34, 38, 39, 40, 41	No	10Mbps down, 5Mbps up. On Band 34 - 41: 6Mbps down, 4 Mbps up.
CAT1-GPS	1, 3, 5, 8, 34, 38, 39, 40, 41	No	10Mbps down, 5Mbps up. On Band 34 - 41: 6Mbps down, 4 Mbps up.
CAT1-EU	1, 3, 7, 8, 20, 28	No	10Mbps down, 5Mbps up
CAT1-EA	1, 3, 5, 7, 8, 28	No	10Mbps down, 5Mbps up

TIP: Check which LTE bands are used by your carrier in your area on cellmapper.net before purchasing a modem..

Enabling All Factory-Supported Bands¶

Example for CAT1-GPS:

Model	AT command
CAT1-GPS	AT*BAND=5,0,0,482,149,1,1,0

Debugging¶

Before attempting any debugging, make sure your SIM card is active and working. Insert it into a phone first, disable the PIN code if necessary, and verify that you can connect to the internet. In some regions, you may need to complete an activation process before the SIM can register on the network.

Connect to the modem using minicom:

minicom -D /dev/ttyACM0 -b 115200

Checking Network Registration¶

Run these commands to check modem status:

AT
AT+CPIN?
AT+COPS?

Example output:

# Check modem availability
AT
AT

OK

# Check SIM status
AT+CPIN?
AT+CPIN?

+CPIN: READY

OK

# Check operator registration
AT+COPS?
AT+COPS?

+COPS: 0,2,"23201",7

OK

23201 is the MCC/MNC (operator code).
The last value 7 indicates LTE connection (other values may indicate GSM/UMTS).

At this point, the modem is successfully registered on the mobile network with LTE access.

Checking IP assignment¶

Registration does not guarantee an active data session. Check your PDP context:

AT+CGDCONT?

Expected output:

AT+CGDCONT?

+CGDCONT: 1,"IP","a1.net","10.54.1.125",0,0

OK

This indicates you have a valid IPv4 address.

If multiple contexts are active:

AT+CGDCONT?

+CGDCONT: 1,"IP","a1.net","10.54.1.125",0,0
+CGDCONT: 2,"IPV6","a1.net","fe80::1234",0,0

OK

List active contexts:

AT+CGACT?

+CGACT: 1,1
+CGACT: 2,1

Disable IPv6 if needed:

AT+CGACT=0,2

NOTE: Context changes may reset after a modem reboot.

AT command cheat sheet¶

Useful commands when evaluating or debugging new modems.

For more advanced scripting, try python ATlib.

Get Firmware version:¶

AT+VER?

Check Network Registration¶

AT+CREG?

# Not connected
+CREG: 0,0

# Connected
+CREG: 0,1

Show Currently Used Band¶

AT*BANDIND?
*BANDIND: 0, 3, 7

Here, the middle number (3) is the LTE band currently in use.

Modem Test¶

The following AT commands must be understood by the modem, otherwise ATlib has to be undated accordingly:

GSM and LTE commands should be understood by any modem, the rest might need some custom adaptations per modem.

# AIR780
get_allowed_bands()
AT*BAND?

get_active_band()
AT*BANDIND?

get_signal_quality()
AT+CESQ

# LTE
get_contexts()
AT+CGDCONT?

get_addresses()
AT+CGPADDR

# GSM
set_operator_auto()
AT+COPS=0

get_current_operator()
AT+COPS?

get_sim_status()
AT+CPIN?

get_version()
AT+VER?

enable_location_reporting()
AT+CREG=2

get_cell_location()
AT+CREG?