The LS1043-S boards have a M.2 Key B slot with SIM designed for use with LTE modems. A list of recommended modems can be found in the Hardware Compatibility List.
We recommend ModemManager for managing the LTE connection, especially since some newer models do not expose full featured AT ports, meaning all communication has to be done through a single userspace process.
LTE Control GPIOs
M.2 modems have a couple of control lines:
|Name||LS1043 GPIO name||Linux GPIO number||Effect of high value (1)||Effect of low value (0)|
|Full_Card_Power_Off#||GPIO4||395||Card powers down||Card is active|
|RESET#||GPIO1||502||Card performs hard reset||Card is active|
|W_DISABLE#||GPIO4||394||Card enters 'airplane mode'||Modem RF is active|
Note: All these lines are connected to the modem via transistors, which means a high value (1) from the host will become a low value (0) to the modem.
Cards with GNSS support might also have a separate disable line (GPS_DISABLE# / pin 26). Due to a lack of available GPIOs on this platform, this has been connected to header P11, via transistor Q3. Both of these components are not usually loaded.
On most cards it is possible to disable and enable GNSS via AT commands.
When LTE and WiFi cards are installed in the same chassis, the use of co-existence filters on the WiFi antennas is recommended.
Depending on the regulatory and telco rules for the region the product is being sold in, additional certification testing may be required before the product can be sold to end users.