IPQ8072A 如何通过AT指令跟SDX55交互

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