Ethernet Module

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Revision as of 00:36, 24 September 2008 by Yan (talk | contribs) (→‎Introduction: clarify the objective)
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Introduction

  • let a device have the following capabilities
    • can be controlled by a general browser in a desktop computer
    • access a server by itself to providing data, such as: device model no., serial no., any application data, or send out email for any events.
  • This project aims to develop an Ethernet Module, to be used in conjunction with a 8/16 bits embedded system such as the dsPic33F development board.
  • Architecture

Bug List

  • DHCP
    • dhcp client fault from buffalo router
    • occasionally cannot access webserver with dhcp
  • DHCP
    • dhcp client fault from main router
    • occasionally cannot access webserver with dhcp
    • possible cause: module tries to get IP configuration when switching on and off too frequently. This causes the router to enter into an unknown state. Even using the static mode with the same IP cannot get Internet access properly. When wait for some time and switch on the module again, the router may have been "reset", and the connection is ok again.


ToDo List

  • 32kB constant limitations
    • see if webserver can be stored in flash in file system
  • SNMP
    • porting snmp to uip
    • reference to lwip
  • SMTP
    • some router cannot used SMTP module
    • the router return its own IP as DNS resolver, and it does support only parsing direct IP function
    • desktop applications (e.g. outlook, thunderbird, webmail) do not use DNS resolver (UDP application) to connect to the mail server, but use TCP/IP to do the job

Hardware

Component List

Special Item Description Quantity
DM9000AEP Ethernet Controller from Davicom 1
HR911102A RJ45 Connector with Integrated Magnetics for 10/100 Base-TX 1
93LC46B-I/SN 1K Serial EEPROM 1 (Optional)
25MHz Crystal Crystal 1
22pF For Crystal Use 2
220uF For RXVDD25/TXVDD25 1
49.9ohm For RX+/RX-/TX+/TX- 4
6.8kohm For BGRES/BGGND 1
510ohm For LEDs 2

Circuit and PCB

in gEDA format and its gEDA sym and footprints


Software Driver

  • Download dm9000a.c
  • Download dm9000a.h
  • Base on FreeRTOS and dsPIC33 platform
  • Using POSIX-like API:
    • int dmfe_open(int flags): initialize the Ethernet controller for 10MHz Half-Duplex
    • int dmfe_close(): turn off the PHY layer
    • int dmfe_read(void): copy a packet to the default buffer
    • int dmfe_write(unsigned char device, unsigned char *buf, int count): copy count bytes of the data from buf and transmit
    • void dmfe_interrupt(void): process the transmit interrupt from DM9000A


TCP/IP Stack

  • uIP and lwIP are light weight TCP/IP Stack designed for 8-bit/16-bit embedded systems.

uIP

  • Develped by Adam Dunkels of the Networked Embedded Systems group at the Swedish Institute of Computer Science.
  • uIP is under the BSD-style license

CVS Repository

Attribute Value
Host uip-stack.cvs.sourceforge.net
Repository Path /cvsroot/uip-stack
Connection Type pserver
User anonymous
  • Changes made to CVS Repository (tag: HEAD v1.1)
    • uip.c
      • Comment out all DEBUG_PRINTF(...) in lines 1, 323, 910, 1015, 1070, 1863, 1868, 1869
    • uip.h
      • Change line 1070 to
        # define HTONS(n) (u16_t)(((((u16_t) (n)) << 8)&0xff00) | ((((u16_t) (n)) >> 8)&0x00ff))
    • psock.c
      • Change line 188 to
        s->sendptr = (u8_t*) buf;
      • Change lines 276, 303 to
        buf_setup(&psock->buf, (u8_t*)(psock->bufptr), psock->bufsize);
      • Change line 334 to
        buf_setup(&psock->buf, (u8_t*)buffer, buffersize);

Porting

  • Include the following files to use the uIP stack
    • timer.c
    • uip.c
    • uip_arp.c
    • psock.c
  • The following files have been created to port uIP 1.0 to dsPic33F development board using FreeRTOS
  • clock-arch.c: return the os tick counts since the system is turned on.
  • clock-arch.h: a constant specifying the number of os ticks in one second.
  • uip-config.h: configuration for your application.

lwIP

  • lwIP is a small independent implementation of uIP.
  • It is more powerful than uIP but requires more memory.
  • lwIP is under the Modified BSD License

CVS Repository

Attribute Value
Host cvs.savannah.nongnu.org
Repository Path /sources/lwip
Connection Type pserver
User anonymous

Porting

  • To be added


uIP Ethernet Application

DHCP Client

  • Enable UDP in "uip-config.h"
     #define UIP_CONF_UDP             1
  • Make sure your uip buffer size is large enough (DHCP messages from some servers can be more than 500 bytes). In my setting, I use 1536 in "uip-config.h"
     #define UIP_CONF_BUFFER_SIZE     1536
  • Include the dhcpc.h header file in "uip-config.h"
     #include "dhcpc.h"
  • Change PT_WAIT_UNTIL(...) to PT_YIELD_UNTIL(...) in line 259 and 276 in "dhcpc.c" [This is a known bug in dhcpc.c]
  • In your main loop, initialize your MAC address and DHCP if UIP_FIXEDADDR is 0 in "uip-opt.h", for example:
  int main(void)
  {
     uip_ipaddr_t ipaddr;
     struct timer periodic_timer, arp_timer;
     struct uip_eth_addr mac = { 0x01, 0x02, 0x03, 0x04, 0x05, 0x06};
     
     timer_set(&periodic_timer, CLOCK_SECOND / 2);
     timer_set(&arp_timer, CLOCK_SECOND * 10);
     
     tapdev_init();
     uip_init();
     
     uip_setethaddr(mac);
     dhcpc_init(&mac, 6);
     
     while(1){
       //normal codes goes here
     }
  }
  • Implement dhcpc_configured(). This function will be called after DHCP client has obtained an IP address. Basically, you have to at least set your IP address, subnet mask and default gateway, for example,
  void dhcpc_configured(const struct dhcpc_state *s)
  {
    uip_sethostaddr(s->ipaddr);
    uip_setnetmask(s->netmask);
    uip_setdraddr(s->default_router);
    
    //you can print your ip addr to your console/lcd to see if you get a valid ip address
  }
  • An example of using DHCP Client in the dsPic33F development board can be found here.

Web Server

  • Include the "webserver.h" header file in "uip-config.h"
     #include "webserver.h"
  • Modify httpd-fs.h
    • HTTPD_FS_STATISTICS set to 0
  • Create a website using HTML tags with/without Javascript
  • Modify httpd-fs.c
    • changed #include "httpd-fsdata.c" to #include <httpd-fsdata.c>
  • Generate httpd-fsdata.c for your website by executing perl makefsdata under your web root directory.

add-on

  • The Web Server included in uIP 1.0 has been designed to load/reload the entire page (either html/shtml files) in response to a HTTP GET command, e.g.
  GET /index.html HTTP/1.1
  GET /abc.shtml HTTP/1.1
  • As a result, if the webpage is required to refresh the dynamic data periodically, the surfing experience will be degraded by the large transfer of datastream.
  • In consideration of the above issue, a solution is proposed here, so that the webserver can handle this kind of cgi HTTP-request
  GET /abc.shtml?val=500.0&button=Set HTTP/1.1
  • Modify httpd.c
    • added #include "httpd-hget.h" in line 63
    • added httpd_hget(s->filename) in line 224
  • Create httpd-hget.h
    • added to generate dynamic pages, e.g. /abc.shtml?button=Refresh
  #ifndef __HTTPD_HGET_H__
  #define __HTTPD_HGET_H__
     extern void httpd_hget(char *name);
  #endif
  • Create httpd-hget.c
    • an example is shown here

SNMP Agent

  • Simple Network Management Protocol (SNMP) is a standard protocol to access variables to remote device via the Internet.
  • It belongs to the Application Layer, as in HTTP.
  • If a device is SNMP compatible, any SNMP compatible host system can monitor and control that device.

Components in a SNMP System

  • Network Management Station (NMS)
    • This is a client, initiating SNMP communication.
    • This can be a PC with an NMS software (e.g. NINO), polling data from the SNMP agents periodically.
  • SNMP Agents
    • These are servers, responding to one or multiple NMS requests.
  • Management Information Base (MIB)
    • A special collection of variables managed by the SNMP agents.
    • MIB has a tree-like structure.
    • An Object Identifier (OID) is given for each node.
    • Data are stored at the end-nodes.
    • Private variables may be constructed under the "enterprise" sub-tree.
    • The OID for "enterprise" can be obtained from Internet Assigned Number Authority (IANA).

Abstract Syntax Notation

  • Each MIB variable contains several attributes, such as data type, access type and object identifier.
  • Abstract Syntax Notation version 1 (ASN.1) is a language to define these attributes in SNMP.


Architecture

                      +--------------------------------------------+--------------------+-------+
 Applications         |            Ethernet Application            |  GUI Application   |  ...  |
                      +--------+--------+---------+----------+-----+                    |       |
 Web Libraries        |  Web   |  DHCP  |  SNMP   |   DNS    | ... |                    |       |
                      | Server |        |         | Resolver |     |                    |       |
                      +--------+--------+---------+----------+-----+                    |       |
 Socket API           |              Linux-like Socket             |                    |       |
                      +--------------------------------------------+                    |       |
 TCP/IP Stack         |                   uip                      |                    |       |
                      +--------------------------------------------+                    |       |
                      |             Ethernet Controller            |                    |       |
                      +--------------------------------------+-----+--------------------+-------+
 POSIX API            |           POSIX System Calls         |           POSIX Threads          |
                      +--------------------------------------+----------------------------------+
                      |               Drivers                |           Task Scheduler         |
                      +--------------------------------------+----------------------------------+


Reference

DM9000A

dsPic33F Development Board

uIP

lwIP

HTML

  • W3 Schools: Learning how to write HTML and JavaScript
  • Nvu: Open source HTML Editor

SNMP

  • SNMP Link: Information on SNMP Agents
  • IANA: Applying a Private Enterprise Number