user manual

HUAWEI ME909u-521 LTE LGA Module

Application Guide

Sleeping and Waking Up Application Scenarios

Issue 01 (2013-07-05)

Huawei Proprietary and Confidential

Figure 8-6 Sleep procedure

8.3.2 USB and Sleep

USB is an important communication channel between the module and the host.

According to the USB protocol, normally a hub or a root hub periodically sends Start

of Frame (SOF) data packages (one data package per ms using full-speed USB and

one package per 125 µs using high-speed USB). Through this mechanism, USB

always votes to stop the module from entering sleep mode.

When the USB driver provided by Huawei detects that the module and the host have

not exchanged data in 5 seconds, the USB driver will enable the port's suspend

feature, stopping SOF data packages being sent and suspending the USB controller.

This enables the USB to vote to agree the module's sleep.