Quectel EC600S-CN - User Manual

EC200x&EC600S&EG912Y Series
PPP Application Note
LTE Standard Module Series
Ver. EC200x&EC600S&EG912Y_Series_PPP_Application_Note_V1.0
Date: 2020-07-31
Status: Released
www.quectel.com

Summary

Introduction to PPP Application Note

PPP Application Mode Overview

PPP Setting Procedures

General Procedures for PPP Setting

Explains setting APN and starting PPP using AT commands.

Recommended Procedures for PPP Setting

Provides a flowchart for PPP setup, covering SIM, network, APN, and packet interaction.

PPP Connection Modes and Handling

Data and Command Modes

Describes module communication modes via USB/UART and their switching.

Handling Data Mode Features

Covers URC handling and DCD mode configuration in data mode.

PPP Connection Termination Methods

PPP Dial-up Operations in Windows

Preparation Steps

Outlines essential steps before establishing a PPP dial-up connection.

Modem Configuration

Guides on adding and configuring the modem and its driver in Windows.

Dial-up Network Configuration

Details on creating and configuring the dial-up network connection.

Establish Dial-up Connection

Guides on establishing the dial-up connection and confirming its status.

Appendix A References

Overview

1. Function Description
2. Usage Features
3. Maintenance Features

This document, the "EC200x&EC600S&EG912Y Series PPP Application Note," provides a comprehensive guide to the Point-to-Point Protocol (PPP) functions of Quectel's LTE Standard EC200x, EC600S, and EG912Y series modules. It covers various aspects including PPP application modes, setting procedures, connection modes, termination steps, and practical dialing examples, primarily focusing on Windows 10 operations. The document is designed to assist users in establishing and managing PPP connections effectively with these modules.

Function Description

The core function of these Quectel modules, as detailed in this application note, is to enable PPP connections over LTE networks. PPP is a data link layer protocol used to establish a direct connection between two nodes. In this context, the modules act as a PPP server, while the application (typically running on a host system like Windows or Linux) functions as a PPP client. Once a PPP connection is established, IP packet data streams from the application are transmitted to the Internet through the module. This allows the host system to access network services and the internet via the cellular module.

The modules support PPP connections via both UART and USB ports. This flexibility allows integration into various system designs, depending on the host's available interfaces. The document emphasizes that the application must also provide higher-layer protocols such as TCP/IP and HTTP(S) to fully utilize the established PPP connection for internet communication.

A key functional aspect is the module's ability to operate in two distinct modes: data mode and command mode. In command mode, the module can execute AT commands for configuration and control. Once a PPP negotiation begins, the module transitions into data mode, where it handles PPP frames. If the PPP connection fails to establish, the module reverts to command mode. This dual-mode operation is crucial for both initial setup and ongoing management of the connection.

The modules also incorporate Data Carrier Detection (DCD) functionality, which can be configured via AT commands (AT&C0 or AT&C1). When AT&C1 is executed, the DCD pin indicates the data carrier status, remaining at a low level when a data carrier is present or PPP negotiation starts, and otherwise staying at a high level. This provides a hardware-level indication of the connection status, which can be useful for external monitoring or control.

Usage Features

The application note outlines several usage features designed to facilitate the establishment and management of PPP connections.

• Flexible Port Options: Users can choose between UART or USB ports for PPP connection, offering adaptability to different hardware setups.
• Standard PPP Protocol Support: The modules adhere to the standard PPP protocol, ensuring compatibility with most operating systems that include a PPP protocol stack (e.g., Windows, Unix/Linux). For systems without a built-in PPP client, custom application software development is required.
• AT Command Interface: Configuration and control of the module's PPP functions are primarily done through AT commands. This includes setting the Access Point Name (APN) using AT+CGDCONT and initiating the PPP dialing process with ATD*99#.
• Mode Switching Mechanisms: The modules provide convenient methods for switching between data mode and command mode.
  • DTR Level Change: By changing the DTR (Data Terminal Ready) level from low to high (after executing AT&D1), the module can switch from data mode to command mode. This is a hardware-assisted method for control.
  • Escape Sequence +++: An alternative software-based method involves sending the +++ escape sequence. Specific timing requirements (no characters 1 second before or after, and +++ within 1 second) must be followed to prevent misinterpretation as data. Upon receiving +++, the module switches to command mode and returns OK.
  • ATO Command: To switch back from command mode to data mode while a PPP connection is maintained, the ATO command can be executed. This allows the host to resume sending PPP frames.
• URC Handling in Data Mode: During an active PPP connection in data mode, Unsolicited Result Codes (URCs) for incoming calls and short messages are not reported directly to the PPP dial-up port. Instead, the module's RI (Ring Indicator) pin changes level (high to low for 120 ms) to indicate a URC. This allows the host MCU to detect URCs and temporarily switch the port to command mode to process them, ensuring that critical notifications are not missed while maintaining data connectivity.
• Recommended PPP Setting Procedures: The document provides a detailed flowchart of recommended procedures for PPP setting, covering steps from power-on/off, (U)SIM card status query, network registration, PS network status query, APN configuration, and packet interaction. This structured approach helps users ensure a robust and reliable PPP connection.
• Windows 10 Dial-up Configuration Example: A step-by-step guide is provided for setting up a PPP dial-up connection in Windows 10. This includes:
  • Modem Configuration: Adding a new standard modem (e.g., "Standard 19200 bps Modem"), selecting the appropriate COM port, and configuring modem driver properties.
  • Modem Driver Settings: Adjusting the "Maximum Port Speed" to "115200" and inputting extra initialization commands like AT+CGDCONT=1,"IP","CMNET" to define the APN.
  • Dial-up Network Configuration: Creating a new dial-up connection, specifying the dial-up phone number (e.g., *99#), and configuring connection properties.
  • Dial-up Tool Configuration: Further configuring the dial-up tool, including hardware features like flow control, error control, and modem compression.
  • Establishing Connection: The process of initiating and verifying the dial-up connection.

Maintenance Features

The document also touches upon aspects related to the maintenance and robustness of the PPP connection.

• Synchronization and Baud Rate Setting: It is crucial to ensure proper synchronization between the MCU and the module after rebooting. For UART, setting and saving the baud rate using AT+IPR=xxx;&W is recommended. This ensures stable communication for AT commands and data.
• Error Handling and Retries: The document provides guidelines for handling command responses and recommends waiting for responses (e.g., OK, CME error, CMS error) within 60 seconds before considering a module restart. It also advises against frequent power-on/off cycles and suggests a structured retry mechanism for dialing failures, with increasing wait times for consecutive failures (immediate reset for 3 failures, then 10 minutes, 30 minutes, and 1 hour for subsequent resets).
• PPP Connection Termination: Two methods are described for terminating the PPP dial-up connection:
  • LCP Terminate-Request Message: This is the recommended method, involving sending an LCP Terminate-Request message through the PPP connection.
  • DTR Level Change: If AT&D2 is set, changing the DTR level from low to high will automatically terminate the data connection. After termination, the USB/UART port reverts to command mode.
• Troubleshooting Guidance: The note implicitly provides troubleshooting guidance by highlighting common issues and their solutions, such as checking network registration status (AT+CREG?, AT+CGREG?), (U)SIM card readiness (AT+CPIN?), and APN configuration (AT+CGDCONT, AT+CGACT?). It also suggests checking PPP configuration and network status if data transmission fails after establishing a PPP connection.
• Documentation and Support: The document itself serves as a key maintenance resource, providing detailed instructions and references. It also directs users to Quectel's headquarters, local offices, and online support channels for further assistance, technical support, or reporting documentation errors. This ensures that users have access to help when encountering issues or needing more information.
• Linux USB Driver User Guide Reference: For users operating in a Linux environment, the document explicitly references the "Quectel_LTE&5G_Linux_USB_Driver_User_Guide," indicating that specific instructions for Linux are available in a separate, dedicated resource. This ensures that users of different operating systems can find relevant guidance.

Quectel EC600S-CN Specifications