Fundamental doubt

[João M. S. Silva]

Hi,

I am using ModemManager to control an HSDPA modem:

$ lsusb
Bus 001 Device 004: ID 12d1:1001 Huawei Technologies Co., Ltd. 
E169/E620/E800 HSDPA Modem

But now we are testing this device: SIM800L from SIMCom.

This modem understands AT commands that we send through a terminal 
program, like miniterm.py or so.

My question is: how does ModemManager relate to AT commands? Is it a 
wrapper for AT commands, i.e. in an higher abstraction layer?

We cannot use ModemManager for this SIM800L module since it uses a 
serial connection and not DBus, is this correct?

Thanks.

-- 
João M. S. Silva