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© MCS Electronics, 1995-2007 |
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Buffer |
A variable or array to get the checksum of. |
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Bytes |
The number of bytes that must be examined. |
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Checksum's are used a lot in communication protocols. A checksum is a way to verify that received data is the same as it was sent. In the TCP/IP protocol a special checksum is used. You can use it for the PING sample.
See also
CRC8 , CRC16, CRC32 , CHECKSUM
ASM
NONE
Example
'-----------------------------------------------------------------------------------------
'name |
: PING_TWI.bas |
http://www.faqs.org/rfcs/rfc792.html |
'copyright |
: (c) 1995-2005, MCS Electronics |
'purpose |
: Simple PING program |
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'micro |
:Mega88 |
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'suited for demo |
: yes |
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'commercial addon needed : no |
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'----------------------------------------------------------------------------------------- |
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' specify the used micro |
$regfile= "m32def.dat" |
$crystal= 8000000 $baud = 19200 $hwstack= 80 $swstack= 128 $framesize = 80
Const Debug = 1
Const Sock_stream = $01
Const Sock_dgram = $02
Const Sock_ipl_raw = $03
Const Sock_macl_raw = $04
Const Sel_control = 0
Const Sel_send = 1
Const Sel_recv = 2
'socket status
Const Sock_closed = $00 Const Sock_arp = $01 Const Sock_listen = $02 Const Sock_synsent = $03
Const Sock_synsent_ack = $04 Const Sock_synrecv = $05 Const Sock_established = $06 Const Sock_close_wait = $07 Const Sock_last_ack = $08 Const Sock_fin_wait1= $09 Const Sock_fin_wait2= $0a Const Sock_closing = $0b Const Sock_time_wait = $0c Const Sock_reset = $0d Const Sock_init = $0e
Const Sock_udp = $0f
'used crystal frequency
'use baud rate
'default use 32 for the hardware stack
'default use 10 for the SW stack
'default use 40 for the frame space
'Tcp
'Udp
'Ip Layer Raw Sock
'Mac Layer Raw Sock
'Confirm Socket Status
'Confirm Tx Free Buffer Size
'Confirm Rx Data Size
'Status Of Connection Closed
'Status Of Arp
'Status Of Waiting For Tcp Connection Setup
'Status Of Setting Up Tcp Connection ' Status Of Setting Up Tcp Connection
'Status Of Setting Up Tcp Connection
'Status Of Tcp Connection Established
'Status Of Closing Tcp Connection
'Status Of Closing Tcp Connection
'Status Of Closing Tcp Connection
'Status Of Closing Tcp Connection
'Status Of Closing Tcp Connection
'Status Of Closing Tcp Connection
'Status Of Closing Tcp Connection
'Status Of Socket Initialization
'Status Of Udp
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© MCS Electronics, 1995-2007 |
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Const Sock_raw = $10 |
' Status of IP RAW |
'we do the usual |
' display a message |
Print"Init TCP" |
EnableInterrupts |
' before we use config tcpip , we need to enable the interrupts |
Config Tcpip = Int0, Mac = 12.128.12.34.56.78 ,Ip= 192.168.0.8 , Submask = 255.255.255.0 , Gateway |
= 192.168.0.1 ,Localport = 1000 ,Tx= $55 ,Rx = $55 ,Twi= &H80 ,Clock = 400000 |
Print"Init done" |
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Dim Peersize As Integer, Peeraddress As Long ,Peerport As Word
Dim IdxAs Byte,Result As Word ,JAs Byte, Res As Byte
Dim IpAs Long
Dim Dta(12)As Byte, Rec(12)As Byte
Dta(1)= 8 |
'type is echo |
Dta(2)= 0 |
'code |
Dta(3)= 0 |
' for checksum initialization |
Dta(4)= 0 |
' checksum |
Dta(5)= 0 |
' a signature can be any number |
Dta(6)= 1 |
' signature |
Dta(7)= 0 |
' sequence number - any number |
Dta(8)= 1 |
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Dta(9)= 65 |
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Dim W As Word At Dta + 2Overlay |
'same as dta(3) and dta(4) |
W = Tcpchecksum(dta(1),9) |
' calculate checksum and store in dta(3) and dta(4) |
#ifDebug |
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For J= 1To 9 |
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Print Dta(j) |
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Next |
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#endif |
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Ip= Maketcp(192.168.0.16) |
'try to check this server |
Print"Socket ";Idx;"";Idx
Setipprotocol Idx,1 'set protocol to 1 'the protocol value must be set BEFORE the socket is openend
Idx= Getsocket(idx,3, 5000 ,0)
Do |
'writepingdata |
' |
Result= Udpwrite(ip,7,Idx,Dta(1),9) |
Print Result |
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Waitms 100 |
'check for data |
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Result= Socketstat(idx,Sel_recv) |
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Print Result |
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IfResult >= 11 Then |
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Print"Ok" |
'get data with TCPREAD !!! |
Res= Tcpread(idx, Rec(1),Result) |
#ifDebug |
' |
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Print"DATA RETURNED :";Res |
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For J= 1To Result |
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Print Rec(j);""; |
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Next |
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Print |
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page -689-
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© MCS Electronics, 1995-2007 |
#endif |
'there might be a problem |
Else |
Print"Network not available" |
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End If |
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Waitms 1000 |
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Loop |
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TCPREAD
Action
Reads data from an open socket connection.
Syntax
Result = TCPREAD( socket , var, bytes)
Remarks
Result A byte variable that will be assigned with 0, when no errors occurred. When an error occurs, the value will be set to 1.
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When there are not enough bytes in the reception buffer, the routine willwait |
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until there is enough data or the socket is closed. |
socket |
The socket number you want to read data from(0-3). |
Var |
The name of the variable that will be assigned with the data from the socket. |
Bytes |
The number of bytes to read. Only valid for non-string variables. |
When you use TCPread with a string variable, the routine will wait for CR + LF and it will return the data without the CR + LF.
For strings, the function will not overwrite the string.
For example, your string is 10 bytes long and the line you receive is 80 bytes long, you wil receive only the first 10 bytes after CR + LF is encountered.
Also, for string variables, you do not need to specify the number of bytes to read since the routine will wait for CR + LF.
For other data types you need to specify the number of bytes.
There will be no check on the length so specifying to receive 2 bytes for a byte will overwrite the memory location after the memory location of the byte.
See also
CONFIG TCPIP, GETSOCKET , SOCKETCONNECT, SOCKETSTAT , TCPWRITE, TCPWRITESTR, CLOSESOCKET , SOCKETLISTEN
Partial Example
Result = Socketstat(idx , Sel_recv) |
' get number of bytes waiting |
If Result > 0 Then |
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Result = Tcpread(idx , S) |
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End If |
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© MCS Electronics, 1995-2007
TCPWRITE
Action
Write data to a socket.
Syntax
Result = TCPWRITE( socket , var , bytes)
Result = TCPWRITE( socket , EPROM, address , bytes)
Remarks
Result |
A word variable that will be assigned with the number of bytes actually |
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written to the socket. |
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When the free transmission buffer is large enough to accept all the data, the |
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result will be the same as BYTES. When there is not enough space, the |
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number of written bytes will be returned. |
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When there is no space, 0 will be returned. |
Socket |
The socket number you want to send data to(0-3). |
Var |
A constant string like "test" or a variable. |
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When you send a constant string, the number of bytes to send does not |
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need to be specified. |
Bytes |
A word variable or numeric constant that specifies how many bytes must be |
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send. |
Address |
The address of the data stored in the chips internal EEPROM. You need to |
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specify EPROM too in that case. |
EPROM |
An indication for the compiler so it knows that you will send data from |
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EPROM. |
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The TCPwrite function can be used to write data to a socket that is stored in EEPROM or in memory.
When you want to send data from an array, you need to specify the element : var(idx) for example.
See also
CONFIG TCPIP, GETSOCKET , SOCKETCONNECT, SOCKETSTAT , TCPWRITESTR, TCPREAD, CLOSESOCKET , SOCKETLISTEN
Example
Result = Tcpwrite(idx , "Hello from W3100A{013}{010}")
TCPWRITESTR
Action
Sends a string to an open socket connection.