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Using PICmicro® MCUs Connect Internet
SOFTWARE LICENSE AGREEMENT
software supplied herewith Microchip Technology Incorporated (the "Company") PICmicro® Microcontroller intended supplied you, Company's customer, solely exclusively Microchip PICmicro Microcontroller products. software owned Company and/or supplier, protected under applicable copyright laws. rights reserved. violation foregoing restrictions subject user criminal sanctions under applicable laws, well civil liability breach terms conditions this license. THIS SOFTWARE PROVIDED CONDITION. WARRANTIES, WHETHER EXPRESS, IMPLIED STATUTORY, INCLUDING, LIMITED IMPLIED WARRANTIES MERCHANTABILITY FITNESS PARTICULAR PURPOSE APPLY THIS SOFTWARE. COMPANY SHALL NOT, CIRCUMSTANCES, LIABLE SPECIAL, INCIDENTAL CONSEQUENTIAL DAMAGES, REASON WHATSOEVER.
1999 Microchip Technology Inc.
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Author: Myron Loewen Microchip Technology Inc.
This Internet interface requires physical connection local Internet Service Provider (ISP) with serial line modem. rest software. algorithm requires about bytes 2170 words ROM. amount processor time available other tasks will depend processor's clock speed baud rate serial connection. algorithm takes time each received transmitted character extra time process create data control packet. This algorithm does include Transmission Control Protocol (TCP) which required email, Telnet, browsing, File Transfer Protocol (FTP). These algorithms could added they require processor with more ROM. This algorithm will connect every server; attempts unscripted login falls back generic script. fails, some login tweaking implementing more Link Control Protocol (LCP) options will usually bring connection.
INTRODUCTION
PICmicro microcontrollers (MCU) suitable lowcost connections Internet. desire connect everything Internet focuses price reduction challenge Internet interface. Typically, interface overpowered embedded running bulky operating system memory intensive applications. low-cost applications that handle smaller amounts data, much better choice Microchip family PICmicro MCUs. This application note will show these little processors capable connecting Internet with resources spare controlling original application. software will dial into Internet connect server using Point Point Protocol (PPP). continues pinging once every seconds keep connection open while responding ping requests. With Internet Protocol (IP) connection established your algorithms traceroute, Trivial File Transfer Protocol (TFTP), Simple Network Management Protocol (SNMP), time date accurate millisecond. Since there lots good books free Internet resources describe Internet works, this application note will focus less publicized details negotiating PPP. Another common protocol used connect Internet modem Serial Line Internet Protocol (SLIP). chosen this application note instead simpler SLIP because much more versatile. advantage requiring unique login script most servers. Another advantage line quality monitoring. Although implemented this algorithm, useful when reliable communications priority. most important reason maintain compatibility with Internet Service Providers riding popularity desktop operating systems, which default.
FIGURE
PHOTO PROTOTYPE CONNECTED INTERNET
FIGURE
BLOCK DIAGRAM
PICmicro Dialer Status LEDs Remote Host Ping IPCP Internet Service Provider
Serial
Modem
Modem
Internet
Ping
Trigger Switch
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INTERNET PROTOCOLS
Internet just very large bunch many types computers connected variety ways. What makes work thousands standards conventions that computers follow. Most standards documented freely available Internet. Table lists standards needed this algorithm where find them. Data gets around Internet specially marked packets that passed from computer computer. packets indicate type data they contain such part page email. Each packet gets stuffed envelope specially marked right program remote computer. This important because running several browsing windows simultaneously machine. type data determines envelope simpler type more robust type. packets generate extra packets open close connection resend lost packets. Each computer gets unique Internet address that looks like 10.241.45.12, works much like postal mailing address. envelope stuffed larger envelope with source destination addresses written front. This like international mail, address will anywhere Internet. Internet works more like passing notes class. larger envelope goes into bigger envelope with your friend's name Your friend opens envelope checks Internet address. recipient, processes otherwise puts envelope. From Internet address tell which direction send envelope puts name neighbor, that direction, front. process repeats until envelope makes correct Internet address across class, gets lost along way. this algorithm only ping packets travel this way. other packets have same format just exchanged locally between this algorithm Internet server dials These packets discussed next sections used both ends configure serial link options. requires serial data format eight data bits with parity. data sent packets that start stop with tilde character hexadecimal 0x7E. Because special meaning, other instance replaced escape sequence. escape sequence works transmitting characters instead original, first then original exored with space character, hexadecimal 0x20. Because special meaning, also escaped same resulting 2-character sequence compatibility with serial links, control characters 0x00 0x1F also optionally mapped into 2-character escape sequence. more complete details, read 1662 HDLC-like Framing. connection broken into several phases. First, link dead, carrier detect from modem stimuli that starts link establishment phase. This phase uses Link Control Protocol (LCP) detect negotiate link options with remote computer. Next authentication phase verifies User password with Password Authentication Protocol (PAP). Although phases, this where ISPs negotiate compression protocols. final phase network layer protocol. Each protocol such configured with control protocol like IPCP. Control protocols very similar LCP, PAP, CCP, IPCP protocol field different options have different meanings. Each packet request, deny, accept list options. Negotiation starts with either side requesting list options request (REQ) packet. Each option consists option type byte, length byte, option parameters. receiving likes options, replies with acknowledge (ACK) packet.
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FIGURE
NEGOTIATION WITH REQ, ACK, NAK, PACKETS
PICmicro
TABLE
Acronym CHAP
ACRONYMS
Description Acknowledgement Compression Control Protocol Cyclic Redundancy Check Challenge-Handshake Authentication Protocol Domain Name System Data Terminal Ready File Transfer Protocol Internet Control Message Protocol Internet Protocol Internet Protocol Control Protocol Internet Service Provider Link Control Protocol Maximum Receive Unit Negative Acknowledgement Password Authentication Protocol Point-to-Point Protocol Reject Request Request Comment Serial Line Internet Protocol Simple Network Management Protocol Transmission Control Protocol Trivial File Transfer Protocol Time Live User Datagram Protocol
Status
LCP-R LCP-R LCP-R LCP-A
Establishing Connection
ICMP IPCP
LCP-R LCP-A PAP-R
PAP-A IPCP-R
Authenticating User
IPCP-A IPCP-R IPCP-N 0.0.0.0 6.52.2.6
Getting Options Address 16.52.2.6
SLIP SNMP TFTP
IPCP-A
CP-RE
16.52.2
16.52.2
doesn't like some parameters, responds with acknowledge (NAK) packet that repeats options rejects replaces rejected parameters with acceptable values. required options missing those added reject list. some options recognized considered non-negotiable they rejected with packet that lists options. first side updates option list retransmits requests until gets reply packet. other side start negotiations time resulting link have different options each direction. terminate, code reject, protocol reject, echo, discard control packet types implemented this algorithm. details broken down into section each control protocol.
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DIAL-UP SCRIPT
cannot start link negotiations without physical connection Internet. this algorithm, dial-up modem makes connection then link negotiated. modem dial script could removed circuits with direct connection server's serial port. sendwait (command, test, timeout) routine does most work script. script sends command string then returns when receives test string time expires. timeout units milliseconds, thus timeout 1000 milliseconds second. First modem taken into command mode with pause, then three plus characters another pause. character command string causes 1-second pause; them where required sendwait() command string. Then, command hangs modem case already hook. AT&F commands then reset modem restore factory default settings. ATS11=50 speeds tone dialing reduce connect time. modem seconds echo command before algorithm aborts assumes modem functioning. algorithm indicates dialing flashing status LED. Then sends dial string modem waits seconds modem respond with connect message before algorithm gives tries whole process again. dial string contains pauses, modem faster than 2400 baud need increase timeout. When modem connects, connection stays steady, otherwise turned off. script waits seconds colon followed space detect when server prompting userID. Whether gets prompt not, sends first packet. This makes fact that most servers switch login instead further text prompts when they first characters packet instead valid User bait taken, script ends negotiation begins. Otherwise script continues sending User password, command enter PPP. address captured this time because IPCP negotiations will capture later.
FIGURE
LOGIN FLOW CHART
Start
Initialize Modem
Modem Ready?
Modem Failed
Dial
Connect?
userID Prompt? Send Packet Header
Reply? Send User
Send Password
Send Command
Login Failure?
Start
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OPTIONS
options negotiated first establish link. sample packet shown Figure normal header 0x7E 0xFF 0x03 followed 0xC0 0x21 indicate that protocol LCP. packet consists code, identification, length, list options configure followed standard byte CRC. code byte indicate meaning packet. list codes found Table identification byte incremented after each negotiation request, which makes requests unique connects them correct reply. 16-bit length number bytes packet, four header plus lengths each option. list possible options found Table Each option sent byte option type, followed byte option length, optional parameter. option length option header plus number bytes parameter. Here brief description more common options: Maximum-Receive-Unit byte parameter maximum size packets. would nice make this value very small conserve buffer space limited PICmicro RAM. However, minimum allowable value much help. Since option benefit safely left 1500 default, this algorithm doesn't waste code space support Note that packets longer than byte buffer size truncated fit, typically longest packet handle about characters. Some ping packets much longer they quite tolerant losing extra padding characters. Async-Control-Character-Map 4-byte parameter this option adds bits: each represents ASCII control characters from Starting with most significant character least significant character character then that character must transmitted sequence. This server client decide escape only characters which cause problems instead wasting bandwidth escaping control characters. Even characters that need escaped this algorithm exploits that simplify software transmit control characters bytes. Authentication-Protocol This option chooses method sending password. Unless have already logged with script, this option will required. parameter value 0xC023 selects Password Authentication Protocol (PAP) which sends packet containing User password plain text. parameter value 0xC223 selects Challenge Handshake Authentication Protocol (CHAP) which User sent plain text password encrypts returns random string from server. server, password encrypts same string; results match, user logged simplicity, this algorithm only supports method. forced CHAP method. Magic-Number This option need implemented negotiations converge. byte parameter random number; identical server's, then both ends choose another random number. Assuming good randomness, chance random numbers being unique after three iterations that transmission path assumed looped back, just echoing packets sent. Protocol-Field-Compression This option parameters. requested, acknowledging side transmit future packets with first byte 2-byte protocol field left out. This meant save bandwidth. easy uncompress byte arrives start protocol field must second byte since first byte always even, second always odd. zero inserted missing first character. This option parameters. However, requested, acknowledging side transmit future packets with second third bytes, 0xFF 0x03, left out. This also meant save bandwidth. also easy decompress because first character packet 0xFF, 0xFF inserted first, second character 0x03, 0x03 inserted first.
other options didn't need implemented make Internet connection, standards evolve future missing option could prevent login. Note that only options number negotiated without modifying TestOptions() routine. word parameter called option which each bits indicate acceptance option. example, Most Significant (MSB) set, then option accepted; cleared, then option rejected. complete when both sides connection have their list acknowledged other side.
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FIGURE SAMPLE REQUEST PACKET
Type Framing Protocol Code Options Framing Checksum Length Payload Length
Data
complete packet with more option details: 0000: 0010:
Same packet with escape sequences: 0000: 0010: 0020: 0030:
TABLE
Type
NEGOTIATION CODES
Packet Type Vendor Specific Configure-Request Configure-Ack Configure-Nak Configure-Reject Terminate-Request Terminate-Ack Code-Reject Protocol-Reject Echo-Request Echo-Reply Discard-Request Identification Time-Remaining Details RFC2153 RFC1661 RFC1661 RFC1661 RFC1661 RFC1661 RFC1661 RFC1661 RFC1661 RFC1661 RFC1661 RFC1661 RFC1570 RFC1570
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TABLE
Type
OPTIONS
Configuration Option Vendor Specific Maximum-Receive-Unit Async-Control-Character-Map Authentication-Protocol Quality-Protocol Magic-Number Quality-Protocol Protocol-Field-Compression FCS-Alternatives Self-Describing-Pad Numbered-Mode Multi-Link-Procedure Callback Connect-Time Compound-Frames Nominal-Data-Encapsulation Multilink-MRRU Proprietary DCE-Identifier Multi-Link-Plus-Procedure Link Discriminator BACP LCP-Authentication-Option Consistent Overhead Byte Stuffing (COBS) Prefix elision Multilink header format Internationalization Simple Data Link SONET/SDH RFC2484 RFC1976 RFC1934 RFC2125 Details RFC2153 RFC1661 RFC1662 RFC1661 RFC1661 RFC1661 Deprecated RFC1661 RFC1661 RFC1570 RFC1570 RFC1663 Deprecated RFC1570 Deprecated Deprecated Deprecated RFC1990 RFC1990 RFC1990
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OPTIONS
details found 1334. this algorithm they were simplified packet exchange. packet similar with 0xC023 instead 0xC021 protocol field. Instead negotiating options, only User password sent request. server acknowledges, then user logged reply would mean that User password incorrect. format seen Figure first payload byte length User followed User password appended same way: Length first followed password.
FIGURE
SAMPLE REQUEST PACKET
Protocol Code 0014 Length userid User Payload password Password Framing Checksum
Framing
complete packet: 0000: 0010:
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IPCP OPTIONS
After negotiated accepted, Internet Protocol must configured. options address Compression with more details 1332. address option three 4-byte parameter Internet address this node. server typically sends request with option three followed address. Otherwise, address found requesting invalid choice like 0.0.0.0 server replies with option three with correct address. sample packet shown Figure Some server implementations request Compression Protocol option type two. These requests rejected because implemented this algorithm. Table shows IPCP configuration option types.
TABLE
Type
IPCP CONFIGURATION OPTION TYPES
Details Deprecated RFC1332 RFC1332 RFC2290 RFC1877 RFC1877 RFC1877
Configuration Option IP-addresses IP-Compression-Protocol IP-address Mobile-IPv4
Primary Server address RFC1877 Primary NBNS Server address Secondary Server address Secondary NBNS Server address
FIGURE
SAMPLE IPCP PACKET
Type IPCP Protocol Code Option Framing Checksum Length
Data
Framing
Length Payload
complete packet: 0000: 0010:
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OPTIONS
Some servers will negotiate compression, since this algorithm optimized size instead speed, these requests rejected. compression algorithms complex some cases proprietary, have little benefit short packets used this algorithm. Choosing puddle jumper option type means that compression decompression required. 0x00 which means normal service with optimization. third fourth bytes total length header plus following data such ICMP message. next bytes fragmented packets since these packets small, this algorithm ignores fragmentation. ninth byte time live (TTL) flag sets maximum number routers packet pass through before discarded. This important keep Internet from getting clogged with lost packets. flag usually decremented each router packet passes through. tenth byte protocol field which says what type information header attached Bytes called header checksum, which one's complement header bytes. implementation details check 1071 which very good description sample code. Basically, 16-bit one's complement data where overflow carries into wrapped around added next bytes source address last four bytes destination address. ICMP message follows with type byte, code byte, checksum word, Figure type byte ping reply ping request. code byte zero both cases checksum again one's complement sum. This time checksum ICMP header plus following data. amount data header total length minus header length. case ping originator stuffs some data properly echoed ping reply. This arbitrary data could just well your collected data other information wish send. This algorithm responds ping requests without echoing back arbitrary data causes some ping programs report error.
ICMP COMMUNICATIONS
Internet Control Message Protocol messages sent with full packets, example shown Figure This protocol used implement ping, many other uses that read about RFCs 950. Ping works sending packet remote Internet address waiting reply, like radar sonar from which gets name. This algorithm pings fixed address once every seconds maintain connection. During this time also responds pings initiated remote devices Internet. description this packet better understood parts, header ICMP message. packets discussed this point were just setting serial link never made past server. more information packed into header. bytes contain instructions take anywhere Internet. first byte broken into nibbles, first bits version which currently still four. next bits header length, which number words header, this case. second byte type service optimize for: minimize delay, maximize throughput, maximize reliability, minimize monetary cost. recommended value ping
FIGURE
Buffer Offset
INTERNET PROTOCOL PACKET SHOWING MEMORY LOCATIONS BUFFER
Length Type Service Flags Protocol Source Address Destination Address ICMP, TCP, Header Data Identification Time Live (TTL) Total Length Bytes Fragment Offset Header Checksum
Version
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FIGURE SAMPLE PING WITH OPTIONAL DATA
Buffer Offset ICMP Type 0000 1000 Version 0100 Length 0101
Service 0000 0000
Total Length 00000000 00011100
Packet 0000
0004 0008 000C 0010 0014 0018 001C 0020
Identification 1000 1000 0001 0000 0111 1111 Protocol 0000 0001
Flags
Fragment Offset 00000 00000000 Header Checksum 00110011 10100111
Source Address 11001101 11001000 00101101 01111100 Destination Address 11001111 10100001 01110101 01000011 ICMP Code 0000 0000 ICMP Checksum 11110111 11111110 PING Sequence Number 00000000 00000000
PING Identifier 00000000 00000001
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DETAILS
protocol required transfer files with TFTP, convert host names addresses with DNS, status event reporting with SNMP. simplicity bandwidth efficiency make important part some multimedia Internet protocols. official specification found 768. This algorithm doesn't support protocols this section will give background make easier algorithm. First unreliable protocol, that should avoided, rather that packets lost without warning require retransmission. deterministic sense that each packet, timeout, triggers next event without regard what state connection This simplifies programming makes debugging much easier. format shown Figure There bytes header, then bytes header, data. first byte fields source destination port numbers. port numbers important identify what process gets data. example port which always used TFTP. next bytes length, eight bytes header plus length data. This value redundant because calculated from header subtracting header length from total length. last bytes header one's complement checksum pseudo header, header, data. pseudo header transmitted following bytes added checksum anyway. source destination addresses, 16-bit address, 8-bit protocol field extended bits ensure that data going correct address. checksum optional zero used. Since zero means checksum, then valid checksum that adds zero must inverted 0xFFFF. data number bytes, your checksum routine will need pretend that there extra byte 0x00 end. format data will depend which port connecting which protocol using data. good example Trivial File Transfer Protocol (TFTP) which well documented 1350.
DETAILS
protocol required transfer files with FTP, communicate email with SMTP, login remotely with Telnet, serve pages with HTTP. original specification found 793; however, been improved Host Requirements RFCs 1122 1123. This algorithm doesn't even pretend support packets because larger requirements. Parts protocol PICmicro MCUs with larger program memory size, here little information those brave enough try. considered reliable protocol because hides lost missing packets from running applications: tracks retransmits them background. This really different than purpose this algorithm since there distinction software levels. both cases same process responsible retransmit missing packets. difference complexity size packets. Another difference that other connection expecting this algorithm keep track packet timing, retransmit previous packets, remember state multiple simultaneous connections.
FIGURE PACKET FORMAT
Buffer Offset Source Port Number Length Header Destination Port Number Checksum Data Such TFTP
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HARDWARE IMPLEMENTATION
This application note designed PIC16C63A demonstrate compact connection algorithm shrunk. algorithm uses file registers 2.2k only pins. There still plenty space your code code portable enough move into smaller larger PICmicro MCU. crystal fast enough could slowed down, unless need faster modem additional intensive tasks. modem Ceremtek CH1786LC, running 2400 baud, with packet sizes under bytes speed much issue. higher traffic connections large data transfers want upgrade larger still pin-compatible 14.4 kilobaud CH1794. sure check with modem manufacturer what external circuitry required before connecting telephone line. Your circuit must designed tested meet telecom standards country which wish Only telephone line, power, serial transmit, receive, line need connected this modem. line must tied modem operate properly. modem very sensitive power supply noise sure keep close bypass capacitor. could also change software little replace modem with RS232 driver directly server's serial port. desirable characteristic this modem that draws maximum Since only brief periods entire circuit never draws more than total easily power battery. typical alkaline battery with 560mA hour rating would give about hours power. modem hook ping time under minute, just send ping hang battery would last more than pings. This works about year half ping day. This requires power supply turn completely after ping successful. power supply design uses transistor turn transistor which supplies current voltage regulator. transistor turned processor momentary switch. When momentary switch closes turns power, microcontroller initializes turns transistor. this time user released switch microcontroller keeps power switch could almost anything like magnetic burglar sensor even thermostat. When ping complete releases power turns itself off. need ping device, just keep manual switch closed until want power off. With switch released, will power down after first successful ping automatic timeout there modem connection, password fails, ping replies. transistor also benefit reducing power consumption because voltage drop lost reverse protection diode. also upgrade dropout (LDO) voltage regulator little extra life battery before volt regulator stops regulating. Choose regulator that includes power switch, change MOSFET reduce current draw another percent battery life. Rather than improving efficiency with DC-DC converter, would choose lower-voltage battery pack with flat discharge curve that barely maintains minimum regulating voltage. device will inaccessible needs long shelf life, then with lithium-ion battery pack. There three LEDs: indicates modem status other indicate serial data transmitted received. modem status while software initalizes modem, flashes quickly while dialing, goes steady when connected. goes after flashing then didn't connect will again couple seconds. After connecting negotiating status light will second then flash address. long flash short flash zero. Write down each flashes then convert binary hexadecimal. Make easier grouping bits fours, each hexadecimal character. Insert three decimals spaced every bits, convert four numbers decimal, have your address, Figure This address usually dynamically assigned resulting different address every time logs Internet. Note: first-time developers PICmicro MCUs, using Microchip PICDEM Demonstration boards (DV163002) useful.
FIGURE CALCULATION ADDRESS FROM PULSES
Record long flashes bit. Record short flashes bit. There will pause every eight flashes. Example: 1100 Hexadecimal: Decimal: 1101 1100 1000 0010 1101 0100 1010
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SOFTWARE IMPLEMENTATION
software written keep portable. This algorithm developed tested with variety low-cost compilers debuggers simply print relevant data screen. Then, just press PrintScreen pipe screen output file analysis. compile replace serial functions with port routines tick counter address `0040:006C' instead TMR0. There number excellent compilers PICmicro MCU. This code started with free compiler CC5X from Knudsen Data Norway completed with PICmicro Compiler from HiTech Australia. code shown will compile with HiTech demo available http://www.htsoft.com. should work with other compilers PICmicro compiler specific modifications required code. code consists main routine that does main tasks modem control scripting protocol state machine. There couple support routines calculating checksums, creating packets, checking configuration options, controlling modem. When press power switch, microcontroller powers does short time delay loop, asserts keep power millisecond time delay meant prevent false triggering. long either user pressing power button asserted power will stay software will release turn power after successfully pings remote host, times trying, fails dial attempts. power button still pressed, software continues dial attempt more pings until button released. example, want ping from another computer will have hold button until complete your ping tests. software will attempt phone number programmed source code times about 30-second intervals. When connects tries going from script login login sending packet instead User that fails, falls back script login; otherwise goes into main loop algorithm. protocol state machine loop does serial I/O, packet processing, packet creation, timing negotiate complete ping. state machine starts state When Internet server acknowledges configuration packet state, set. When algorithm acknowledges server's configuration, set. long clear, algorithm will send request once every second. When both bits algorithm moves into state state four request with User password sent once second. acknowledgement password moves algorithm into state five. When algorithm acknowledges server's IPCP options moves into state six. state algorithm requests address 0.0.0.0 once second. server should reply with packet containing correct address move algorithm into final state Here flashes address status then pings hardcoded host address every seconds. After first good ping reply, turns power unless power button still pressed. MakePacket routine creates outgoing packet transmit buffer. Every loop state machine checks serial transmitter ready another character. transmit buffer empty, sends next character. last character marks buffer empty sends extra 0x7E mark packet. Every loop state machine also checks serial receiver characters from modem Internet server. Characters that sent using previously described escape sequence immediately converted back original character. checksum also calculated bytes come that packets longer than buffer still pass CRC. OptionTest routine used test receive buffer whatever options server requesting. takes 16-bit option parameter, where each represents option from with being MSB. set, then corresponding option accepted. server requests options that allowed option parameter, then subroutine returns zero deletes options that were allowed. This packet sent tell server which options drop. packet with option three CHAP then subroutine returns deletes options that passed. This packet sent tell server switch PAP. other cases subroutine returns value greater than leaves receive buffer unchanged.
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FIGURE NEGOTIATION STATE MACHINE
REQ/NAK State Connection State Channel Ready REQ/NAK REQ/NAK State Connected Automatic State Authenticating User State Configuring IPCP IPCP REQ/ACK State Requesting Address IPCP State Ready Ping Send Requests REQ/NAK Send Requests State Channel Ready REQ/NAK Send Requests
IPCP REQ/REJ
IPCP NAK/REQ
Send IPCP Requests
Send Ping Requests
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CONCLUSION
This algorithm little taste what possible with PICmicro MCU, will likely this information basis even more powerful Internet applications. Just remember only make small changes working code test them before making next change. This information quite technical, don't give already TCP/IP savvy. Remember that called experts learn some time too. Read book like TCP/IP Illustrated Volume Richard Stevens referenced RFCs, then compile code analyze lots packets. Start your experimenting slowly with relatively easy task like adding support replying Traceroute requests. Here's hint: test valid packets received trigger sending ICMP error packet. This tutorial meant encourage development tiny Internet interfaces replace override established Internet standards documents. prototype does what needed there many areas which could improved upon, such size, speed, power requirements, usage, supported protocols, more universal negotiations. possibilities only limited your imagination creativity overcoming obstacles.
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TABLE REFERENCES
W.R. Stevens, TCP/IP Illustrated, Vol. Addison Wesley, Reading, 1994 James Carlson, Design Debugging, Addison Wesley, Reading, 1997 0768 User Datagram Protocol. Postel. Aug-28-1980. 0791 Internet Protocol. Postel. Sep-01-1981. 0792 Internet Control Message Protocol. Postel. Sep-01-1981. 0793 Transmission Control Protocol. Postel. Sep-01-1981. 0867 Daytime Protocol. Postel. May-01-1983. 0950 Internet Standard Subnetting Procedure. J.C. Mogul, Postel. Aug-01-1985. 1055 Nonstandard transmission datagrams over serial lines: SLIP. J.L. Romkey. Jun-01-1988. 1071 Computing Internet checksum. R.T. Braden, D.A. Borman, Partridge. Sep-01-1988. 1122 Requirements Internet hosts communication layers. R.T. Braden. Oct-01-1989. 1123 Requirements Internet hosts application support. R.T. Braden. Oct-01-1989. 1144 Compressing TCP/IP headers low-speed serial links. Jacobson. Feb-01-1990. 1157 Simple Network Management Protocol J.D. Case, Fedor, M.L. Schoffstall, Davin. May-01-1990. 1332 Internet Protocol Control Protocol (IPCP). McGregor.May 1992. 1334 Authentication Protocols. Lloyd, Simpson. October 1992. 1350 TFTP Protocol (Revision Sollins. July 1992. 1547 Requirements Internet Standard Point-to-Point Protocol. Perkins. December 1993. 1570 Extensions. Simpson. January 1994. 1661 Point-to-Point Protocol (PPP). Simpson, Editor. July 1994. 1662 HDLC-like Framing. Simpson, Editor. July 1994. 1663 Reliable Transmission. Rand. July 1994. 1700 Assigned Numbers. Reynolds, Postel. October 1994. 1962 Compression Control Protocol (CCP). Rand. June 1996. 1989 Link Quality Monitoring. Simpson. August 1996. 1994 Challenge Handshake Authentication Protocol (CHAP). Simpson. August 1996. RFCs available online from sites like: Assigned Numbers:
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7-35V 2.2k
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FIGURE SCHEMATIC
Vbatt
2N2907
79L05
Optional Else Short Trigger
PIC16C63A MCLR
CH1786LC
2N2222
RING
OSC1 OSC2
RJ11
Vbatt
Legend:
AN724
Status Power
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APPENDIX SOURCE CODE
SOFTWARE LICENSE AGREEMENT
software supplied herewith Microchip Technology Incorporated (the "Company") PICmicro® Microcontroller intended supplied you, Company's customer, solely exclusively Microchip PICmicro Microcontroller products. software owned Company and/or supplier, protected under applicable copyright laws. rights reserved. violation foregoing restrictions subject user criminal sanctions under applicable laws, well civil liability breach terms conditions this license. THIS SOFTWARE PROVIDED CONDITION. WARRANTIES, WHETHER EXPRESS, IMPLIED STATUTORY, INCLUDING, LIMITED IMPLIED WARRANTIES MERCHANTABILITY FITNESS PARTICULAR PURPOSE APPLY THIS SOFTWARE. COMPANY SHALL NOT, CIRCUMSTANCES, LIABLE SPECIAL, INCIDENTAL CONSEQUENTIAL DAMAGES, REASON WHATSOEVER.
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APPENDIX SOURCE CODE
PING.C version 1.10 July 29/99 (C)opyright Microchip Technology Inc. more documentation read Microchip Application Note This code ready compile with HiTech compiler demo PIC16C63A. will need these additional things make this code work: simple hardware described application note Internet account with dialup access (not compatible with ISPs) replace 5551234 with your ISP's phone number line like this replace userid with your account userid line like this: replace password with your account password line like this: replace entire string line like this: converts \x## string character with that ASCII value hexadecimal value, following character cannot next character then will confuse compiler solution convert next characters \x## until char doubt look assembly output from compiler replace userid with yours \x06 with your userid length replace password with yours \x08 with your password length replace first value string, must string length plus Once login working should also change address Internet host ping ping 207.161.117.67 with your this code will work either CF.A1.75.43, characters string line like this: Convert address want hexadecimal replace four values. Make sure power-on reset brownout detect config bits enabled Defines Internet constants #define #define #define #define #define TERM #define 0x0021 #define IPCP 0x8021 #define 0x80FD #define 0xC021 #define 0xC023 #define #define MaxRx MaxTx
Request options list negotiations Acknowledge options list negotiations acknowledged options list negotiations Reject options list negotiations Termination packet close connection Internet Protocol packet Internet Protocol Configure Protocol packet Compression Configure Protocol packet Link Configure Protocol packet Password Authentication Protocol packet
Maximum size receive buffer Maximum size transmit buffer
unsigned char addr1, addr2, addr3, addr4;// Assigned address unsigned rx_ptr, tx_ptr, tx_end; pointers into buffers unsigned checksum1, checksum2; checksums
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unsigned char number; #include <pic1663.h> #define #define #define #define #define #define #define serial_init() serial_tx_ready() serial_send(a) serial_rx_ready() serial_get() serial_error() serial_fix() Unique packet Defines specific this processor serial port TXIF Transmitter empty TXREG=a Transmit char RCIF Receiver full RCREG Receive char OERR USART error {CREN=0;CREN=1;} Clear error milliseconds counter millisecond counter value Transmitter buffer Receiver buffer
unsigned TIME; #define TIME_SET(a) TIME=a bank1 unsigned char tx_str[MaxRx+1]; bank1 unsigned char rx_str[MaxTx+1];
Process interrupts here static void interrupt isr(void) (T0IF) Timer overflow interrupt? TMR0 100; overflow again 10ms 4MHz T0IF Clear overflow interrupt flag TIME++; Increment counter next character checksum packets unsigned calc(unsigned char Just loop index 0xFF; Only calculate byte (i=0;i<8;i++) Loop eight times, once each (c&1) high? Position next 0x8408; Toggle feedback bits else Just position next This routine would best optimized assembly return Return checksum character packet void add(unsigned char checksum2 calc(c^checksum2) (checksum2/256); from this char running total tx_str[tx_ptr] Store character transmit buffer tx_ptr++; Point next empty spot buffer Create packet type, code, length, data string specified packet type, like code type packet like REQ, used packets packet LCP, data type packets *str packet data added after header returns packet string tx_str void MakePacket(unsigned packet, unsigned char code, unsigned char num, const unsigned char *str) unsigned length; Just dual temp variable tx_ptr Point second character transmit buffer tx_str[0] first character space checksum2 0xFFFF; Initialize checksum add(0xFF); Insert header OxFF add(3); Insert header 0x03 add(packet/256); Insert high byte protocol field add(packet&255); Insert byte protocol field (packet==IP) Internet Protocol add(0x45); Insert header version length add(0); Insert type service add(0); Insert total packet length high byte
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add((*str)+12); Insert total packet length byte add(0x88); Insert identification high byte add(0x10); Insert identification byte add(0x40); Insert flags fragment offset add(0); Insert rest fragment offset add(127); Insert time live countdown add(num); insert protocol field length high byte checksum packet *str 0x10 addr2 addr4 str[2] str[4]; byte checksum packet length/256; make complement length (length&255) packet/256; adding carry high byte packet (packet&255) length/256; adding high carry byte length packet/256; adding carries add(~length); Insert complement checksum high byte add(~packet); Insert complement checksum byte add(addr1); Insert bytes this login's address add(addr2); add(addr3); add(addr4); length *str save number following data bytes str++; point first data byte else add(code); Insert packet type, like add(num); Insert packet number add(0); Insert most significant byte length length *str point first data byte while (length) copy whole string into packet length-; decrement packet length add(*str); current character packet str++; point next character length ~checksum2; invert checksum add(length&255); Insert checksum add(length/256); Insert checksum tx_end=tx_ptr; buffer marker packet tx_ptr Point beginning packet Test option list packet valid passwords option field, where high accepts option greater than returns NAK, only correct fields found, zero means options return also modifies RX_STR list unacceptable options required unsigned char TestOptions(unsigned option){ unsigned size; size length option string unsigned ptr1 ptr1 points data insert location ptr2 ptr2 points data origin char pass pass return value size rx_str[7]+4; size length packet (size>MaxRx) size=MaxRx; truncate packet larger than buffer while (ptr1<size) scan options receiver buffer (rx_str[ptr1]==3 rx_str[ptr1+2]!=0x80 rx_str[2]==0xc2) pass&=0xfd; found CHAP request, mark pass=0; found illegal options, mark ptr1 rx_str[ptr1+1]; point start next option (!(pass&2)) marked (pass&1) save state option=0xfffb; (ptr1=8; ptr1<size;) illegal option (pass=rx_str[ptr1+1]; ptr1<size pass; ptr1++) move option rx_str[ptr2]=rx_str[ptr1]; move current byte storage
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ptr2++; pass-; else ptr1+=rx_str[ptr1+1]; rx_str[7] ptr2-4; pass=0; (option==0xfffb) pass=1; return pass; Send string loop until wait string arrives times send string transmit wait string wait timeout multiples milliseconds addr1 used control status LED, 0=off, 1=flash, 2=on returns timeout, returns wait string matched char sendwait(const char *send, const char *wait, unsigned timeout) addr2=addr3=0; (TIME_SET(0); TIME<timeout; loop until time runs (!addr1) PORTB&=0xFB; addr1=0 turn status else (addr1==1) addr1=1 flash status (TIME&4) PORTB&=0xFB; flash period 10ms else PORTB|=4; else PORTB|=4; addr1>1 turn status (serial_rx_ready()) there incoming character PORTB|=1; turn addr4 serial_get(); character (serial_error()) serial_fix(); clear serial errors (wait[addr2]==addr4) addr2++; does char match wait string else addr2=0; otherwise reset match pointer PORTB&=0xFE; turn (!wait[addr2]) return finished string matches else (send[addr3] (serial_tx_ready())) char send ready (send[addr3]=='|') pause character (TIME>100) second expired yet? TIME_SET(0); clear timer addr3++; point next character else PORTB|=2; turn TIME_SET(0); clear timer, timeout starts after last char serial_send(send[addr3]); send character addr3++; point next char string PORTB&=0xFD; turn (!send[addr3] !(*wait)) return done string wait string return return with indicate timeout void flash(void) (TIME_SET(0);;) (TIME&8) PORTB|=0x07; else PORTB&=0xF8; (TIME>3000) PORTB&=0xF7; void pulse(unsigned char data) TIME_SET(0); flash LEDs catastrophic failure flash period 10ms after seconds turn power increment storage pointer decrement number characters
point next option
save option string length restore state restore state
pulse Status with address
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for(number=0;number<9;) pulse address bits blank (TIME<100) PORTB&=0xFB; turn Status between bits else (number<8) PORTB|=4; start each address here (TIME>200 (!(data&0x80) TIME>120)) bit? TIME_SET(0); yes, then restart timer next number++; increment counter data<<=1; position address send next main loop, login script, state machine, ping transponder void main(void) signed serial character received unsigned packet Type last received packet, reused temp unsigned char state negotiation state, from dialing=0 done=6 unsigned char extended flag last character escape sequence PORTA=0; PORTB=0; PORTC=0; TRISA=0; TRISB=0x00; TRISC=0xC0; OPTION=0x85; INTCON=0xA0; serial_init(); TIME_SET(0); while (TIME<25); PORTB=8;
Turn power supply, turn LEDs Turn into outputs
TIMER millisecond counting
Initialize serial port 2400 baud format millisecond delay prevent false power Turn power user release power button
for(number=1;;number++) Redial indefinitely every seconds (number==10) PORTB&=0xF7; Turn power dialing fails addr1=0; flag keep Status Init modem flash(); addr1=1; flag flash Status Modify this line with your phone number addr1=2; flag keep Status (sendwait("",": ",1000)) Wait user prompt break; Start else Fallback script required Modify these lines described (!sendwait("ppp\r","IP address",200)) Modify start command sendwait("2\r","IP address",200); break; State machine loop until successful ping negotiation timeout (TIME_SET(0);;) (TIME>7000 number>20) PORTB&=0xF7; (serial_rx_ready()) Incoming character? PORTB ^=1; Turn serial_get(); character (serial_error()) serial_fix();// clear errors 0x7E) start packet (rx_ptr (checksum1==0xF0B8)) packet rx_str[2]*256 rx_str[3]; passes accept packet extended 0x7E; clear escape character flag
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rx_ptr ready next packet checksum1 0xFFFF; start checksum else 0x7D) tilde character escape flag extended else (extended&1) escape flag 0x20; recover next character extended 0xFE; clear escape flag (rx_ptr==0 c!=0xff) rx_str[rx_ptr++] 0xff; uncompress header (rx_ptr==1 c!=3) rx_str[rx_ptr++] (rx_ptr==2 (c&1)) rx_str[rx_ptr++] rx_str[rx_ptr++] insert character buffer (rx_ptr>MaxRx) rx_ptr MaxRx;// pointer buffer checksum1 calc(c^checksum1) (checksum1/256); calculate checksum PORTB&=0xFE; turn Status else (tx_end (serial_tx_ready())) Data send empty? PORTB|=2; turn tx_str[tx_ptr]; character from buffer (tx_ptr==tx_end) last character tx_end=0; mark buffer empty c='~'; send tilde character last PORTB&=0xFD; turn else (extended&2) sending escape sequence? c^=0x20; then convert character extended 0xFD; clear escape flag tx_ptr++; point next char else (c<0x20 c==0x7D c==0x7E) escape sequence required? extended escape flag 0x7D; send escape character else (!tx_ptr) c='~'; send first character packet tx_ptr++; serial_send(c); character transmitter (packet LCP) switch (rx_str[4]) Switch packet type case REQ: state 0xfd; clear remote ready state (c=TestOptions(0x00c6)) option request list (c>1) ACK; packet (state<3) state 2;// remote ready state else rx_str[10]=0xc0; else password authentication NAK; else else options REJ; TIME_SET(0); create packet from buffer break; case ACK: (rx_str[5]!=number) break;// does reply match request (state<3) state local ready flag break; case NAK: state 0xfe; Clear local ready flag break; case REJ: state 0xfe; Clear local ready flag break;
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case TERM: break; (state==3) state When both ends ready, state else (packet PAP) switch (rx_str[4]) Switch packet type case REQ: break; Ignore incoming case ACK: state means this state done break; case NAK: break; Ignore incoming else (packet IPCP) switch (rx_str[4]) Switch packet type case REQ: (TestOptions(0x0004)) move next state ACK; state else otherwise reject options REJ; break; Create IPCP packet from buffer case ACK: (rx_str[5]==number) IPCP response matches request state Move into final state pulse(addr1); Pulse Status show pulse(addr2); address pulse(addr3); pulse(addr4); PORTB|=4; Turn Status after pulsing TIME_SET(5800); Move timer ahead quicker PING break; case NAK: This where address addr1 rx_str[10]; addr2 rx_str[11]; Store address packets addr3 rx_str[12]; addr4 rx_str[13]; break; Make IPCP packet from buffer case REJ: break; Ignore incoming IPCP case TERM: break; Ignore incoming IPCP TERM else (packet (state<7 (rx_str[19]==addr4 rx_str[18]==addr3 rx_str[17]==addr2 rx_str[16]==addr1)) ignore echoed packets from address before reach state power down here because echoes good indications that modem connection hung-up This would good place insert traceroute test response else (rx_str[13]==1) packet with ICMP payload (rx_str[24]==8) Received PING request rx_str[20]=rx_str[16]; Copy origin address bytes destination address rx_str[21]=rx_str[17]; rx_str[22]=rx_str[18]; rx_str[23]=rx_str[19]; rx_str[19]=16; Length address(4) ping protocol(8) rx_str[24]=0; Change received ping request(8) ping reply(0) packet rx_str[28]+rx_str[30];// Calculate comp checksum
1999 Microchip Technology Inc.
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rx_str[26] packet&255; rx_str[27] packet/256; packet rx_str[27] packet&255; packet packet/256 rx_str[26]; rx_str[26] packet&255; rx_str[27] packet/256; rx_str[26] ~rx_str[26]; Invert checksum bits rx_str[27] ~rx_str[27]; MakePacket(IP,0,1,rx_str+19);// Make packet from modified buffer else (rx_str[24]==0) Received PING reply PORTB&=0xF7; Turn power after successful ping else (packet CCP) switch (rx_str[4]) response matches request case REQ: REJ; (TestOptions(0x0004)) ACK; option only, anything else Create packet from buffer else (packet) Ignore other received packet types else (!tx_end (state==0 state==2) TIME>100) Once second negotiating number++; Increment make packets unique TIME_SET(0); Reset timer Request options 2,7,8 else (!tx_end state TIME>100) Once second negotiating password TIME_SET(0); Reset timer number++; format like Modify this line described above else (!tx_end state TIME>100) Once second negotiating IPCP number++; Increment make packets unique TIME_SET(0); Reset timer Request IPCP option with addr 0.0.0.0 else (!tx_end state TIME>3000) Every seconds ping TIME_SET(0); Reset timer number++; Increment ping count Ping 207.161.117.67 packet Indicate that packet processed
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Microchip received QS-9000 quality system certification worldwide headquarters, design wafer fabrication facilities Chandler Tempe, Arizona July 1999. Company's quality system processes procedures QS-9000 compliant PICmicro® 8-bit MCUs, KEELOQ® code hopping devices, Serial EEPROMs microperipheral products. addition, Microchip's quality system design manufacture development systems 9001 certified.
rights reserved. 1999 Microchip Technology Incorporated. Printed USA. 11/99
Printed recycled paper.
Information contained this publication regarding device applications like intended suggestion only superseded updates. representation warranty given liability assumed Microchip Technology Incorporated with respect accuracy such information, infringement patents other intellectual property rights arising from such otherwise. Microchip's products critical components life support systems authorized except with express written approval Microchip. licenses conveyed, implicitly otherwise, under intellectual property rights. Microchip logo name registered trademarks Microchip Technology Inc. U.S.A. other countries. rights reserved. other trademarks mentioned herein property their respective companies.
1999 Microchip Technology Inc.
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