WAVESHARE RM500U-CN 5G Hat Driver User Guide

WAVESHARE RM500U-CN 5G Hat Driver

INTRODUCTION

This document mainly introduces how to integrate the USB-to-serial driver and USB network card driver of Quectel 5G modules RG500U-CN and RM500U-CN into Linux system, how to test AT command and USB network card dial-up function, and common problems related to driver migration.

OVERVIEW OF LINUX USB INTERFACE

The USB drivers of Quectel RG500U-CN and RM500U-CN modules contain several different functional interfaces. The following table takes RG500U-CN as an example to describe the details of the module’s USB interface under the Linux

Table 1: Linux USB Interface Information

3: LOG Port
4: AT Command Communication Port
5：Modem Command Communication Port
6: NMEA Command Communication Port
USBFS| 7: ADB Command Communication Port

LINUX USB DRIVER

USB TO SERIAL PORT

When the module successfully loads the USB-to-serial option driver, Linux will create multiple serial device files with names such as ttyUSB0, ttyUSB1, ttyUSB2, etc. name).

The following chapters introduce how to change USB to serial port option driver

ADD VID AND PID

Add the module’s VID and PID information in the file [KERNEL]/drivers/usb/serial/option.c as follows:

Note
If the user uses the driver file (option.c) provided by Quectel, it is recommended that the user check the option_probe function in [KERNEL]/drivers/usb/serial/option.c. According to the introduction in Chapter 2, the module interface 2/3/4/5/6 is the serial port. It is necessary to ensure that the interface after the USB interface number exceeds 4 will not be filtered out.

ADD THE ZERO PACKET MECHANISM

For the USB Bulk Out transmission mode, if the length of the data to be sent is an integer multiple of the length of the USB data packet, an additional data packet with a length of zero needs to be sent to notify the peer end that the data transfer is complete.

• For Linux kernel 2.6.35 and above, please add the following statement to the file KERNEL]/drivers/usb/serial/usb_wwan.c.
  

• For Linux kernel 2.6.34 and below, please add the following statement to the file [KERNEL]/drivers/usb/serial/option.c
  

ADD RESET-RESUME MECHANISM

Some USB host controllers or USB hubs may power down or reset when the MCU enters suspend or sleep mode, and the MCU cannot automatically resume USB devices after exiting suspend or sleep mode. Add the following statement to enable reset recovery flow.

• For Linux kernel 3.5 and above, please add the following statement to the file [KERNEL]/drivers/usb/serial/option.c
  

• For Linux kernel 3.4 and below, please add the following statement to the file [KERNEL]/drivers/usb/serial/usb-serial.c
  

INCREASE THE QUANTITY AND CAPACITY OF THE BULK OUT URBS (LINUX KERNEL 2.6.29 AND BELOW)

For Linux kernel 2.6.29 and below, the number and capacity of batch output URBs need to be increased to obtain faster uplink rate. Please add the following statement to the file [KERNEL]/drivers/usb/serial/option.c.

MODIFY KERNEL CONFIGURATION

In order to use the USB-to-serial option driver, the following Linux kernel configuration items must beenabled:

• CONFIG_USB_SERIAL
• CONFIG_USB_SERIAL_WWAN
• CONFIG_USB_SERIAL_OPTION

USB NETWORK CARD DRIVER

The module supports four network card functions of MBIM/RNDIS/ECM/NCM. The Linux system supports these USB network card functions by default. The system has a built-in driver module and does not require any modification to the driver files of the Linux system. The driver source code is maintained by GNU Linux. After the module is connected to the Linux Host and successfully loaded with the corresponding network card driver for USB, a network card will be generated on the Host. cdc_mbim also generates a cdc-wdm character device for command interaction. The network card mode of the module can be configured by AT commands, as shown in the following table:

Mode
RNDIS| rndis_host| AT+QCFG=”usbnet”,3  Configure RNDIS Mode
NCM| cdc_ncm| AT+QCFG=”usbnet”,5  Configure NCM Mode

For details on the above AT commands, please refer to document [1].

To use the USB NIC function, follow the steps below to configure the kernel. Step

Step 1: Execute the following command to switch to the kernel directory.
CD< KERNEL content>
Step 2: Execute the following commands to set environment variables and export the defconfig file inthe user device operating system.

Step 3: Execute the following command to compile the kernel.

Step 4: Execute the following command to enable the USB network card function through the options shown in the figure below.

ENABLE PPP DIALING (NOT RECOMMENDED)

PPP dial-up has the following disadvantages compared to the USB network card Internet access method:

• More complicated to use
• Higher CPU consumption under the same internet speed
• The data transmission cannot reach the theoretical rate

Therefore, PPP dialing is not recommended. If required, the following Linux kernel configuration items must be enabled:

• CONFIG_PPP
• CONFIG_PPP_ASYNC
• CONFIG_PPP_SYNC_TTY
• CONFIG_PPP_DEFLATE

AT AND USB NETWORK CARD DIAL-UP FUNCTION TEST

AT FUNCTION TEST

After the module successfully loads the USB-to-serial option driver, Linux will create multiple serial device files with names such as ttyUSB0, ttyUSB1, ttyUSB2, etc. in the /dev directory (the serial device file names under Linux are not fixed, and the system automatically assigns available names ), where the third serial port is the AT command port of the module. A serial port tool such as minicom or busy box microcom can be used to test AT functionality. The following figure shows the AT function result tested by the busy box microcosm tool. The thirdserial port name assigned by the system in the example is /dev/ttyUSB2.

USB NETWORK CARD DIAL TEST

For details of USB network card dialing, please refer to the document [2]

FAQ

HOW TO CHECK WHETHER USB DRIVER EXISTS IN THE MODULE

The list of files under the directory /sys/bus/usb/drivers can be used to see which USB drivers have been existed to the Linux system. E.g

If you need to change USB to serial driver, please make sure option exists. If you need to port the USBNCM driver, please make sure that cdc ncm exists;
If you need to port the USB ECM driver, please ensure that cdc ether exists; if you need to migrate the USB MBIM driver, please ensure that cdc mbim exists;
To port USB RNDIS driver, make sure rndis host exists.

HOW TO CHECK WHETHER THE MODULE WORKS WELL WITH THE CORRESPONDING USB

DRIVER

This chapter shows the corresponding log information printed by the Linux system when the module loads the USB driver correctly. Users can check whether the module has correctly loaded the USB driver by comparing the logs in this chapter with the actual logs obtained.

APPENDIX A REFERENCES

Reference Document

Module AT Command Manual
[2]| QuectelRG500U-CN&RM500U-CN Network Dial Guide| QuectelRG500U-CN&RM500U CN  Network Dial Application Guide

Terms and Abbreviations

CUSTOMER SUPPORT

www.waveshare.com/wiki

References

• Waveshare Wiki

Read User Manual Online (PDF format)

Read User Manual Online (PDF format)  >>

Download This Manual (PDF format)

Download this manual  >>