root@imx6qsabresd:~# busybox microcom /dev/mhi_DUN 
[  384.652992] [I][mhi_uci_open] Node open, ref counts 1
[  384.658144] [I][mhi_uci_open] Starting channel
[  384.662612] [I][__mhi_prepare_channel] Entered: preparing channel:32
[  384.680397] [I][mhi_dump_tre] carl_ev evt_cmd_comp code=1
[  384.685890] [I][__mhi_prepare_channel] Chan:32 successfully moved to start state
[  384.693312] [I][__mhi_prepare_channel] Entered: preparing channel:33
[  384.708692] [I][mhi_dump_tre] carl_ev evt_cmd_comp code=1
[  384.714324] [I][__mhi_prepare_channel] Chan:33 successfully moved to start state

RDY

+CFUN: 1

+CPIN: READY

+QUSIM: 1

+QIND: SMS DONE

+QIND: PB DONE
ati
Quectel
EM20
Revision: EM20GR01A01M4G

OK
at+cpin?
+CPIN: READY

OK