Quectel_GSM_MQTT_Application_Note_V1.2(C).pdf Quectel_MC20&MC30_AT_Commands_Manual_V1.2.pdf Quectel_MC20&MC30_GNSS_AGPS_应用指导_V1.2.pdf Quectel_MC20&MC30_GNSS_AGPS_应用指导_V1.3.pdf Quectel_MC20&MC30_GNSS_Protocol_Specification_V1.2.pdf Quectel_MC20_AT_Com