| In recent years,a new generation of mobile communication technology about LTE networks are being builded on a large scale at home and abroad.However,construction and maintenance of LTE network are lack of effective and reliable monitoring means.The market urgently needs a kind of instrument monitoring the LTE network status.LTE instrument as a combination platform of hardware and software is closely related to the embedded technology.The key technology points in embedded system are BootLoader and device drivers.This article focus on drivers of embedded LTE instrument based on ARM,which includes two parts:the research and transplantation of U-boot,the research and implementation of network card driver based on embedded Linux.Our final goal is to complete the normal boot of LTE instrument and the correct communication of network card driver.This paper first analyzes the basic principle of the U-boot,which startup is divided into two stages.The first statge,which codes are written in assembly language,does some work about ARM,such as setting ARM exceptions table,banning IRAM remapping,configuring DDR and so on.The second stage which codes are written in C language,does some work about LTE board devices,such as setting the baud rate,configuring network card and so on.Then do the transplantation of U-boot.Second this paper ananlyzes the basic principle of embedded Linux network card driver,in detail.This includes framework of Linux network,some key struct like net_device,sk_buff,and the principle of packet-sending and packet-receiving.The receiving of packet can use three mechanism:interrupt mode,poll mode and NAPI mode.Then this paper gives some key codes of core operating methods about network device,such as probe function,open function,sending function,interrupt function and poll function.At last,this article do function and performance testing and assessing. |
