LooUQ provides several integration circuit boards to facilitate the integration of our modems into your project or product. However you can also directly integrate our modems into your project. 

This guide covers the physical mounting and connections from your host system to each of the LooUQ LTEm modems. 


The CR-LTEM1 and CR-LTEM2 have the same same physical form, dimensions and signal logic. They also share a common electrical interface with only one minor differences. The LooUQ LTEm UXplor integration boards work with both of these devices. The CR-LTEM3F and CR-LTEM4K are LooUQ modems with different physical forms and interface characteristics.

The LTEm modem boards are 45mm x 40mm. The host interface connector extends out 3mm from the board (16.8mm wide, centered); the host interface header (2 x 8) is designed to mate with a right-angle header (Adam Tech 2PH2R-16-UA, Digikey 2057-2PH2R-16-UA-ND). At the opposite end of the board are two mounting holes designed to accept snap-fit pins (Keystone Electronics 8880, Digikey 36-8880-ND). 

LTEm2 STEP Model

LTEm2 STEP Model

Online Autodesk STEP Viewer

The diagram below shows the dimensions for host boards for electrical and mounting infrastructure. For more detailed information on the modem, including component heights see the linked LTEM2 STEP file.

Power/Signal Interface

All of the interface signals are 3.3 volt logic level. The LTEm series requires 3.7 volt (nominal) supply voltage; 3.6 - 4.2 volt standard LiPo battery power. The interface pin assignments are found in the table below.


Signal directions are referenced from the modem; In signifies a host signal that controls the modem, Out is a signal from the modem to the host.

Pin (from left)
Signal Name
1VBATPowerPower in, standard 3.7 volt LiPo expected
2GNDPowerSystem ground
3MOSISignal-InSPI data out (from host modem)
4MISOSignal-OutSPI data in (from modem to host)
5~CSSignal-InSPI chip-select (inverted logic, GND=true)
6CLKSignal-InSPI clock
7~IRQSignal-OutCTA IRQ (inverted logic, GND=true)
8TXSignal-InLTEm1: Not used
LTEm2: The command/Data in, direct to the BGx module
(requires the SPI/HDR jumper be in the HDR position)
9RXSignal-OutLTEm1: The NMEA sentence output
LTEm2: The command/data from the BGx module
10PwrKeySignal-InPower state (pulse on/off to toggle LTEm power state)
11ResetSignal-InResets modem
Note: this is not used by the LTEmC device software.
12~WakeSignal-InInstructs modem to wake
Note: this is not currently used by the LTEmC device software.
13StatusSignal-OutIndicates that the modem is powered on and operating. This signal coincides with the green LED indicator.
14ConnectedSignal-OutIndicates that the LTEm is connected
Note: this is not used by the LTEmC device software.
15EventSignal-OutWhen toggled, signals that the LTEm has a new event to be serviced.
Note: this is not used by the LTEmC device software.
16N/ANot Connected

~ prefixed items indicates inverted signal (true when low)