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RL-ARM User's Guide (MDK v4)

RL-RTX RL-FlashFS RL-TCPnet TCP Socket Opening TCP Connection TCP Active Open TCP Passive Open Sending TCP Data Example for Sending Data Multiple TCP Connections UDP Socket Opening UDP Connection Sending UDP Data When DHCP Enabled When ARP Cache Empty Example for Sending Data IP Multicasting Multiple UDP Connections Configuring RL-TCPnet Static Configuration System Definitions Ethernet Network Interface PPP Network Interface SLIP Network Interface UDP Socket TCP Socket BSD Socket HTTP Server Telnet Server TFTP Server TFTP Client FTP Server FTP Client DNS Client SMTP Client SNMP Agent SNTP Client Error Function Runtime Configuration Library Files Using RL-TCPnet Stand Alone With RTX Kernel Event Driven Operation IP Address Assignment Ethernet Interface PPP Interface SLIP Interface Localhost Applications HTTP Server Script Language CGI Functions Ajax Support Using XML XML Example How it works SOAP Support SOAP Interface Large POST Messages Web Pages Default Page Error Pages Web on SD Card Web Update File System Interface Http Caching How it works Internal Web External Web Multi-user Authentication Using RAM File System FCARM File Converter PRINT Directive NOPRINT Directive PAGEWIDTH Directive PAGELENGTH Directive ROOT Directive Telnet Server Command Line Interface Multi-user Authentication Sending Reply Message Short Reply Long Reply Continuous Screen Update TFTP Server File System Interface TFTP Client File System Interface FTP Server File System Interface Multi-user Authentication Supported Commands FTP Client File System Interface SMTP Client SNMP Agent MIB Database MIB Interface MIB Entry MIB Table DNS Resolver Starting DNS Device Drivers Ethernet Driver Interrupt Mode Modem Driver Serial Driver Using Serial Link Cable Connection Modem Connection Windows Dial-up Add Direct Serial Link New Dial-up Connection Configure PPP Dial-up Configure SLIP Dial-up Debugging Enabling Debug Debug Level Redirecting Output Function Overview BSD Routines CGI Routines Ethernet Routines FTP Routines HTTP Routines IGMP Routines Miscellaneous Routines Modem Routines PPP Routines Serial Routines SLIP Routines SMTP Routines SNMP Routines System Functions TCP Routines Telnet Routines TFTP Routines UDP Routines RL-CAN RL-USB Example Programs Library Reference Appendix

Cable Connection

If you want to connect the embedded device directly to a computer, you must use the Null Modem driver. The figure belows shows an overview of a directly connected system.

Cable Connection to Single PC

However, RL-TCPnet's Null Modem driver supports two different procedures for establishing the null modem serial link with the computer:

  • Windows Direct Serial Link. This is a non-modem link. This system requires the exchange of string tokens between the computer and the embedded device before the PPP link can be negotiated. The SLIP link needs no negotiation because SLIP is a simple protocol over a serial line.

    The Windows client sends the string "CLIENT". The Keil evaluation board must then send the string "CLIENTSERVER". When operating as a server, the Keil evaluation board must send the string "CLIENT". The Windows client must respond with the string "CLIENTSERVER".

    This string exchange must occur before Windows allows the PPP connection to proceed. This string exchange is peculiar to Windows and is not required by other hosts.
  • Windows Standard Modem Link. In this system, the Null Modem driver simulates an external modem. The PPP source must also be modified to operate with the Windows direct serial driver. It requires the exchange of modem command strings between the computer and the evaluation board before the PPP link can be negotiated. The strings to be exchanged are shown in the table below.

    Windows Command Reply Description
    AT\r OK\r Attention Command
    ATE0V1\r OK\r Set No echo and Verbose Result reply
    AT\r OK\r Attention Command
    ATS0=0\r OK\r Disable Modem Auto Answer
    AT\r OK\r Attention Command
    ATE0V1\r OK\r Set No echo and Verbose Result reply
    AT\r OK\r Attention Command
    ATDTxxxxxxx\r CONNECT\r Dial Target number: xxxxxxx

    After the "CONNECT" string is received, Windows starts the PPP negotiations and user authentication.

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