'-----------------------------------------------------------
' Atmega168 and ENC28J60       -        ARP, PING and Telnet
'-----------------------------------------------------------
' Version 1.0 - june 2007 by Ben Zijlstra
' august 2007 addins by Viktor Varga

'fusebits:
'Atmega168 - External clock (from 6.25 Mhz to 12.5 Mhz) No div by 8

$regfile = "m644def.dat"
$crystal = 20000000                                         '12500000
$baud = 19200                                               'put terminal on 19200 baud

$hwstack = 90
$swstack = 90
$framesize = 90

$include "enc28j60.inc"

$lib "tcpip.lbx"

'Enc28j60_cs Alias Portb.2
Enc28j60_cs Alias Portb.4
'Led Alias Portb.1

'Constants
'Maximum frame length - The Atmega168 has only 1024 byte internal RAM!
Const Max_framelen = 550                                    '550 byte will be enough for common tasks
Const Urg = 5
Const _ack = 4
Const Psh = 3
Const Rst = 2
Const Syn = 1
Const Fin = 0
Const Tcp_data = 55

Config Enc28j60_cs = Output
'Config Led = Output
'Set Led                                                     'Turn off the tuxgraphics board LED

'Global DIM's
Dim X As Word
Dim A(5) As Byte
Dim Enc28j60_bank As Byte
Dim Enc28j60_data As Byte
Dim Enc28j60_wdata As Word
Dim Enc28j60_nextpacketptr As Word
Dim Enc28j60_value As Byte
'
Dim Buffer(max_framelen) As Byte
'
Dim I_chksum32 As Long
Dim I_checksum16 As Word
Dim I_value16 As Word
Dim I_value16h As Byte At I_value16 + 1 Overlay
Dim I_value16l As Byte At I_value16 Overlay
'
Dim Myip(4) As Byte
Dim My_ip As Long At Myip Overlay
'
Dim Mymac(6) As Byte
'
Dim Tempword As Word
Dim Tempwordh As Byte At Tempword + 1 Overlay
Dim Tempwordl As Byte At Tempword Overlay

Dim Tcp_fin As Bit
Dim Tcp_syn As Bit
Dim Tcp_rst As Bit
Dim Tcp_psh As Bit
Dim Tcp_ack As Bit
Dim Tcp_urg As Bit

Dim Synflag As Bit

Dim Packetlength As Word

'Overlays of ethernetpacket
'
'Ethernet packet destination
Dim T_enetpacketdest0 As Byte At Buffer Overlay
Dim T_enetpacketdest1 As Byte At Buffer + &H01 Overlay
Dim T_enetpacketdest2 As Byte At Buffer + &H02 Overlay
Dim T_enetpacketdest3 As Byte At Buffer + &H03 Overlay
Dim T_enetpacketdest4 As Byte At Buffer + &H04 Overlay
Dim T_enetpacketdest5 As Byte At Buffer + &H05 Overlay
'Ethernet packet source
Dim T_enetpacketsrc0 As Byte At Buffer + &H06 Overlay
Dim T_enetpacketsrc1 As Byte At Buffer + &H07 Overlay
Dim T_enetpacketsrc2 As Byte At Buffer + &H08 Overlay
Dim T_enetpacketsrc3 As Byte At Buffer + &H09 Overlay
Dim T_enetpacketsrc4 As Byte At Buffer + &H0A Overlay
Dim T_enetpacketsrc5 As Byte At Buffer + &H0B Overlay
'Ethernet packet type
Dim T_enetpackettype0 As Byte At Buffer + &H0C Overlay
Dim T_enetpackettype1 As Byte At Buffer + &H0D Overlay
'Arp
Dim T_arp_op1 As Byte At Buffer + &H15 Overlay
'arp source ip address
Dim T_arp_sipaddr0 As Byte At Buffer + &H1C Overlay
Dim T_arp_sipaddr1 As Byte At Buffer + &H1D Overlay
Dim T_arp_sipaddr2 As Byte At Buffer + &H1E Overlay
Dim T_arp_sipaddr3 As Byte At Buffer + &H1F Overlay
'arp target IP address
Dim T_arp_tipaddr0 As Byte At Buffer + &H26 Overlay
Dim T_arp_tipaddr1 As Byte At Buffer + &H27 Overlay
Dim T_arp_tipaddr2 As Byte At Buffer + &H28 Overlay
Dim T_arp_tipaddr3 As Byte At Buffer + &H29 Overlay
'IP header layout IP version and header length
Dim T_ip_vers_len As Byte At Buffer + &H0E Overlay
'Arp
Dim T_arp_op0 As Byte At Buffer + &H14 Overlay
'arp source mac address
Dim T_arp_src_enetpacket0 As Byte At Buffer + &H16 Overlay
Dim T_arp_src_enetpacket1 As Byte At Buffer + &H17 Overlay
Dim T_arp_src_enetpacket2 As Byte At Buffer + &H18 Overlay
Dim T_arp_src_enetpacket3 As Byte At Buffer + &H19 Overlay
Dim T_arp_src_enetpacket4 As Byte At Buffer + &H1A Overlay
Dim T_arp_src_enetpacket5 As Byte At Buffer + &H1B Overlay
'arp source mac address
Dim T_arp_dest_enetpacket0 As Byte At Buffer + &H20 Overlay
Dim T_arp_dest_enetpacket1 As Byte At Buffer + &H21 Overlay
Dim T_arp_dest_enetpacket2 As Byte At Buffer + &H22 Overlay
Dim T_arp_dest_enetpacket3 As Byte At Buffer + &H23 Overlay
Dim T_arp_dest_enetpacket4 As Byte At Buffer + &H24 Overlay
Dim T_arp_dest_enetpacket5 As Byte At Buffer + &H25 Overlay
'Buffer length
Dim T_ip_pktlen0 As Byte At Buffer + &H10 Overlay
Dim T_ip_pktlen1 As Byte At Buffer + &H11 Overlay
Dim T_id0 As Byte At Buffer + &H12 Overlay
Dim T_id1 As Byte At Buffer + &H13 Overlay

'Dim T_flags As Byte At Buffer + &H14 Overlay

'protocol (ICMP=1, TCP=6, UDP=11)
Dim T_ip_proto As Byte At Buffer + &H17 Overlay
'header checksum
Dim T_ip_hdr_cksum0 As Byte At Buffer + &H18 Overlay
Dim T_ip_hdr_cksum1 As Byte At Buffer + &H19 Overlay
Dim T_ip_hdr_cksum As Word At Buffer + &H18 Overlay
'IP address of source
Dim T_ip_srcaddr0 As Byte At Buffer + &H1A Overlay
Dim T_ip_srcaddr1 As Byte At Buffer + &H1B Overlay
Dim T_ip_srcaddr2 As Byte At Buffer + &H1C Overlay
Dim T_ip_srcaddr3 As Byte At Buffer + &H1D Overlay
Dim T_ip_srcaddr As Long At Buffer + &H1A Overlay
'IP address of destination
Dim T_ip_destaddr0 As Byte At Buffer + &H1E Overlay
Dim T_ip_destaddr1 As Byte At Buffer + &H1F Overlay
Dim T_ip_destaddr2 As Byte At Buffer + &H20 Overlay
Dim T_ip_destaddr3 As Byte At Buffer + &H21 Overlay
Dim T_ip_destaddr As Long At Buffer + &H1E Overlay
Dim T_icmp_type As Byte At Buffer + &H22 Overlay
Dim T_icmp_code As Byte At Buffer + &H23 Overlay
Dim T_icmp_cksum0 As Byte At Buffer + &H24 Overlay
Dim T_icmp_cksum1 As Byte At Buffer + &H25 Overlay
Dim T_icmp_cksum As Word At Buffer + &H24 Overlay

Dim Tcp_srcporth As Byte At Buffer + &H22 Overlay
Dim Tcp_srcportl As Byte At Buffer + &H23 Overlay

Dim Tcp_destporth As Byte At Buffer + &H24 Overlay
Dim Tcp_destportl As Byte At Buffer + &H25 Overlay

Dim Tcp_seqnum3 As Byte At Buffer + &H26 Overlay
Dim Tcp_seqnum2 As Byte At Buffer + &H27 Overlay
Dim Tcp_seqnum1 As Byte At Buffer + &H28 Overlay
Dim Tcp_seqnum0 As Byte At Buffer + &H29 Overlay

Dim Tcp_acknum3 As Byte At Buffer + &H2A Overlay
Dim Tcp_acknum2 As Byte At Buffer + &H2B Overlay
Dim Tcp_acknum1 As Byte At Buffer + &H2C Overlay
Dim Tcp_acknum0 As Byte At Buffer + &H2D Overlay

Dim Tcp_hdr As Byte At Buffer + &H2E Overlay

Dim Tcp_flags As Byte At Buffer + &H2F Overlay
Dim Tcp_cksumh As Byte At Buffer + &H32 Overlay
Dim Tcp_cksuml As Byte At Buffer + &H33 Overlay
Dim Tcp_cksum As Word At Buffer + &H32 Overlay

Dim Seqnum As Long
Dim Seqnum3 As Byte At Seqnum Overlay
Dim Seqnum2 As Byte At Seqnum + 1 Overlay
Dim Seqnum1 As Byte At Seqnum + 2 Overlay
Dim Seqnum0 As Byte At Seqnum + 3 Overlay

Dim Acknum As Long
Dim Acknum3 As Byte At Acknum Overlay
Dim Acknum2 As Byte At Acknum + 1 Overlay
Dim Acknum1 As Byte At Acknum + 2 Overlay
Dim Acknum0 As Byte At Acknum + 3 Overlay

'Declares
Declare Sub Enc28j60_reset
Declare Sub Enc28j60_setextclock
Declare Sub Enc28j60_init
Declare Sub Enc28j60_version
Declare Sub Enc28j60_readcontrolregbyte(byval Register As Byte)
Declare Sub Enc28j60_writecontrolregbyte(byval Register As Byte , Byval Enc28j60_value As Byte)
Declare Sub Enc28j60_selectbank(byval Enc28j60_bank As Byte)
Declare Sub Enc28j60_bitfield_set(byval Register As Byte , Byval Enc28j60_value As Byte)
Declare Sub Enc28j60_bitfield_clear(byval Register As Byte , Byval Enc28j60_value As Byte)
Declare Sub Enc28j60_readphyword(byval Phyregister As Byte)
Declare Sub Enc28j60_writephyword(byval Phyregister As Byte , Byval Enc28j60_wdata As Word)
Declare Sub Enc28j60_packetsend(byval Pcktlen As Word)
Declare Sub Enc28j60_packetreceive
Declare Sub Enc28j60_poll

Declare Sub Arpreply
Declare Sub Pingreply
Declare Sub Setip_id
Declare Sub Setipaddrs
Declare Sub Tcp
Declare Sub Ip_header_checksum
Declare Sub Icmp_checksum
Declare Sub Tcp_checksum
Declare Sub Srcdestchksum
Declare Sub Telnet
Declare Sub Ack2tcp_ack
Declare Sub Seq2tcp_seq
Declare Sub Swapsrc2dest
Declare Sub Swapdestport2srcport
Declare Sub Optiona
Declare Sub Optionb
Declare Sub Optionc
Declare Sub Optionquit

'Settings
'MAC address
Mymac(1) = &H43
Mymac(2) = &HC6
Mymac(3) = &HB3
Mymac(4) = &HF3
Mymac(5) = &HAB
Mymac(6) = &H9E

'IP address
Myip(1) = 192
Myip(2) = 168
Myip(3) = 0
Myip(4) = 61

'Start mainprogram

'Configuration of the SPI-bus
Config Spi = Hard , Interrupt = Off , Data Order = Msb , Master = Yes , Polarity = Low , Phase = 0 , Clockrate = 4 , Noss = 0

'init the spi pins
Spiinit

'Reset the Enc28J60
Call Enc28j60_reset
Call Enc28j60_setextclock

Print
Print "Starting Tux"

Call Enc28j60_version
Call Enc28j60_init

Do
   Call Enc28j60_poll
Loop

End

'***************** start of the ENC28J60-routines *******************************


Sub Enc28j60_reset
   Enc28j60_cs = 0
   'reset ENC28J60
   X = Enc28j60_soft_reset
   Spiout X , 1
   Enc28j60_cs = 1
   Do
   Call Enc28j60_readcontrolregbyte(estat)
   X = Enc28j60_data.estat_clkrdy
   Loop Until X = 1
End Sub


Sub Enc28j60_setextclock
   'clock from default divide/4 (6.25 Mhz) to divide/2 (12.5 Mhz)
   Call Enc28j60_writecontrolregbyte(ecocon , &B00000010)
   Waitms 250
End Sub


Sub Enc28j60_version
   Call Enc28j60_selectbank(3)
   'EREVID
   A(1) = &B000_10010
   Enc28j60_cs = 0
   Spiout A(1) , 1
   Spiin A(1) , 2
   Print "Enc28j60-version = " ; A(2)
   Enc28j60_cs = 1
End Sub


Sub Enc28j60_init
   'do bank 0 stuff
   'initialize receive buffer
   '16-bit transfers, must write low byte first
   'set receive buffer start address
   Enc28j60_nextpacketptr = Rxstart_init
   Enc28j60_value = Low(rxstart_init)
   Call Enc28j60_writecontrolregbyte(erxstl , Enc28j60_value)
   Enc28j60_value = High(rxstart_init)
   Call Enc28j60_writecontrolregbyte(erxsth , Enc28j60_value)
   'set receive pointer address
   Enc28j60_value = Low(rxstart_init)
   Call Enc28j60_writecontrolregbyte(erxrdptl , Enc28j60_value)
   Enc28j60_value = High(rxstart_init)
   Call Enc28j60_writecontrolregbyte(erxrdpth , Enc28j60_value)
   'set receive buffer end
   Enc28j60_value = Low(rxstop_init)
   Call Enc28j60_writecontrolregbyte(erxndl , Enc28j60_value)
   Enc28j60_value = High(rxstop_init)
   Call Enc28j60_writecontrolregbyte(erxndh , Enc28j60_value)
   'set transmit buffer start
   Enc28j60_value = Low(txstart_init)
   Call Enc28j60_writecontrolregbyte(etxstl , Enc28j60_value)
   Enc28j60_value = High(txstart_init)
   Call Enc28j60_writecontrolregbyte(etxsth , Enc28j60_value)
   'do bank 2 stuff
   'enable MAC receive
   Enc28j60_value = 0
   Enc28j60_value.macon1_marxen = 1
   Enc28j60_value.macon1_txpaus = 1
   Enc28j60_value.macon1_rxpaus = 1
   Call Enc28j60_writecontrolregbyte(macon1 , Enc28j60_value)
   'bring MAC out of reset
   'enable automatic padding and CRC operations
   Enc28j60_value = 0
   Enc28j60_value.macon3_padcfg0 = 1
   Enc28j60_value.macon3_txcrcen = 1
   Enc28j60_value.macon3_frmlnen = 1
   Call Enc28j60_writecontrolregbyte(macon3 , Enc28j60_value)
   'set inter-frame gap (non-back-to-back)
   Call Enc28j60_writecontrolregbyte(maipgl , &H12)
   Call Enc28j60_writecontrolregbyte(maipgh , &H0C)
   'set inter-frame gap (back-to-back)
   Call Enc28j60_writecontrolregbyte(mabbipg , &H12)
   'set the maximum packet size which the controller will accept
   Enc28j60_value = Low(max_framelen)
   Call Enc28j60_writecontrolregbyte(mamxfll , Enc28j60_value)
   Enc28j60_value = High(max_framelen)
   Call Enc28j60_writecontrolregbyte(mamxflh , Enc28j60_value)

   'bank 3 stuff
   Call Enc28j60_writecontrolregbyte(maadr5 , Mymac(1))
   Call Enc28j60_writecontrolregbyte(maadr4 , Mymac(2))
   Call Enc28j60_writecontrolregbyte(maadr3 , Mymac(3))
   Call Enc28j60_writecontrolregbyte(maadr2 , Mymac(4))
   Call Enc28j60_writecontrolregbyte(maadr1 , Mymac(5))
   Call Enc28j60_writecontrolregbyte(maadr0 , Mymac(6))
   'no loopback of transmitted frames
   Call Enc28j60_writephyword(phcon2 , Phcon2_hdldis)
   'switch to bank 0
   Call Enc28j60_selectbank(0)
   'enable interrupts
   Enc28j60_value = 0
   Enc28j60_value.eie_intie = 1
   Enc28j60_value.eie_pktie = 1
   Call Enc28j60_bitfield_set(eie , Enc28j60_value)

   'filters according to Guido
   Call Enc28j60_writecontrolregbyte(epmm0 , &H3F)
   Call Enc28j60_writecontrolregbyte(epmm1 , &H30)
   Call Enc28j60_writecontrolregbyte(epmcsl , &HF9)
   Call Enc28j60_writecontrolregbyte(epmcsh , &HF7)

   Enc28j60_value = 0
   Enc28j60_value.erxfcon_pmen = 1                          'Pattern Match enable (ARP only)
   Enc28j60_value.erxfcon_ucen = 1                          'Unicast enable
   Call Enc28j60_bitfield_set(erxfcon , Enc28j60_value)

   Enc28j60_value = 0
   Enc28j60_value.erxfcon_bcen = 1                          'Broadcast disable
   Call Enc28j60_bitfield_clear(erxfcon , Enc28j60_value)
   'CRC check is enabled by default

   'Something is wrong with the Broadcast filter (or the whole theory), it seems
   'like every packet is coming in

   'enable packet reception
   Enc28j60_value = 0
   Enc28j60_value.econ1_rxen = 1
   Call Enc28j60_bitfield_set(econ1 , Enc28j60_value)

   'Reset transmit logic
   Enc28j60_value = 0
   Enc28j60_value.econ1_txrst = 1
   Call Enc28j60_bitfield_set(econ1 , Enc28j60_value)
   Call Enc28j60_bitfield_clear(econ1 , Enc28j60_value)
End Sub


Sub Enc28j60_selectbank(enc28j60_bank As Byte)
   'get ECON1 (BSEL1 en BSEL0)
   A(1) = &B000_11111
   Enc28j60_cs = 0
   Spiout A(1) , 1
   Spiin A(1) , 2
   Enc28j60_cs = 1
   A(2) = A(2) And &B1111_1100                              'strip bank part
   A(2) = A(2) Or Enc28j60_bank
   A(1) = &B010_11111
   Enc28j60_cs = 0
   Spiout A(1) , 2
   Enc28j60_cs = 1
End Sub


Sub Enc28j60_writecontrolregbyte(register As Byte , Enc28j60_value As Byte)
   Enc28j60_bank = 0
   If Register.7 = 1 Then Enc28j60_bank = 2
   If Register.6 = 1 Then Enc28j60_bank = Enc28j60_bank + 1
   Register = Register And &B00011111
   Call Enc28j60_selectbank(enc28j60_bank)
   Register.6 = 1                                           'to get a 010_register
   A(1) = Register
   A(2) = Enc28j60_value
   Enc28j60_cs = 0
   Spiout A(1) , 2
   Enc28j60_cs = 1
End Sub


Sub Enc28j60_readcontrolregbyte(register As Byte)
   Local Mcphy As Byte
   Enc28j60_bank = 0
   Mcphy = 0
   If Register.7 = 1 Then Enc28j60_bank = 2
   If Register.6 = 1 Then Enc28j60_bank = Enc28j60_bank + 1
   If Register.5 = 1 Then Mcphy = 1
   Register = Register And &B00011111
   Call Enc28j60_selectbank(enc28j60_bank)
   A(1) = Register
   Enc28j60_cs = 0
   Spiout A(1) , 1
   Spiin A(1) , 3
   Enc28j60_cs = 1
   'Depending of register (E, MAC, MII) yes or no dummybyte
   If Mcphy = 1 Then
      Enc28j60_data = A(2)
      Else
      Enc28j60_data = A(3)
   End If
End Sub


Sub Enc28j60_bitfield_set(register As Byte , Enc28j60_value As Byte)
   Enc28j60_bank = 0
   If Register.7 = 1 Then Enc28j60_bank = 2
   If Register.6 = 1 Then Enc28j60_bank = Enc28j60_bank + 1
   Register = Register And &B00011111
   Call Enc28j60_selectbank(enc28j60_bank)
   Register = Register Or &B100_00000
   A(1) = Register
   A(2) = Enc28j60_value
   Enc28j60_cs = 0
   Spiout A(1) , 2
   Enc28j60_cs = 1
End Sub


Sub Enc28j60_bitfield_clear(register As Byte , Enc28j60_value As Byte)
   Enc28j60_bank = 0
   If Register.7 = 1 Then Enc28j60_bank = 2
   If Register.6 = 1 Then Enc28j60_bank = Enc28j60_bank + 1
   Register = Register And &B00011111
   Call Enc28j60_selectbank(enc28j60_bank)
   Register = Register Or &B101_00000
   A(1) = Register
   A(2) = Enc28j60_value
   Enc28j60_cs = 0
   Spiout A(1) , 2
   Enc28j60_cs = 1
End Sub


Sub Enc28j60_readphyword(phyregister As Byte)
   'set the right address and start the register read operation
   Call Enc28j60_writecontrolregbyte(miregadr , Phyregister)
   Call Enc28j60_writecontrolregbyte(micmd , Micmd_miird)
   'wait until the PHY read complets
   Do
   Call Enc28j60_readcontrolregbyte(mistat)
   Loop Until Enc28j60_data.mistat_busy = 0
   'quit reading
   Call Enc28j60_writecontrolregbyte(micmd , 0)
   'get data value
   Call Enc28j60_readcontrolregbyte(mirdl)
   Enc28j60_wdata = Enc28j60_data
   Shift Enc28j60_wdata , Left , 8
   Call Enc28j60_readcontrolregbyte(mirdh)
   Enc28j60_wdata = Enc28j60_wdata + Enc28j60_data
End Sub


Sub Enc28j60_writephyword(phyregister As Byte , Enc28j60_wdata As Word)
   Call Enc28j60_readphyword(phyregister)
   Local Temp As Byte
   'set the PHY register address
   Call Enc28j60_writecontrolregbyte(miregadr , Phyregister)
   Call Enc28j60_readcontrolregbyte(miregadr)
   Temp = Miregadr
   Enc28j60_value = Low(enc28j60_wdata)
   Call Enc28j60_writecontrolregbyte(miwrl , Enc28j60_value)
   Enc28j60_value = High(enc28j60_wdata)
   Call Enc28j60_writecontrolregbyte(miwrh , Enc28j60_value)
   Do
   Call Enc28j60_readcontrolregbyte(mistat)
   Loop Until Enc28j60_data.mistat_busy = 0
End Sub


Sub Enc28j60_poll
   Call Enc28j60_readcontrolregbyte(epktcnt)
   If Enc28j60_data > 0 Then
      Call Enc28j60_packetreceive
   End If
End Sub


Sub Enc28j60_packetreceive
   'Reset Led
   Local Length As Word
   Local Wtemp As Word
   Local Rxstat As Word
   'set the read pointer to the start of the received packet
   Enc28j60_value = Low(enc28j60_nextpacketptr)
   Call Enc28j60_writecontrolregbyte(erdptl , Enc28j60_value)
   Enc28j60_value = High(enc28j60_nextpacketptr)
   Call Enc28j60_writecontrolregbyte(erdpth , Enc28j60_value)
    Enc28j60_cs = 0
    'Send Read Buffer Memory command
    Spdr = &H3A
    Do
    Loop Until Spsr.spif0 = 1
    'Get the first 6 byte (3 word: Nextpacketptr, Packetlength, Rxstat)
    For X = 1 To 6
          Spdr = &HFF                                       'SPI read
          Do
          Loop Until Spsr.spif0 = 1                         'SPI ready
          Buffer(x) = Spdr
    Next X
    Enc28j60_nextpacketptr = Buffer(2) * 256
    Enc28j60_nextpacketptr = Enc28j60_nextpacketptr + Buffer(1)
    Length = Buffer(4) * 256
    Length = Length + Buffer(3)
    Rxstat = Buffer(6) * 256
    Rxstat = Rxstat + Buffer(5)
    'Get the payload
    Length = Length - 4                                     'Discard CRC
    For X = 1 To Length
          Spdr = &HFF                                       'SPI read
          Do
          Loop Until Spsr.spif0 = 1                         'SPI ready
          Buffer(x) = Spdr
    Next X
    Enc28j60_cs = 1
   'move the rx read pointer to the start of the next received packet
   'this frees the memory we just read out
   Enc28j60_value = Low(enc28j60_nextpacketptr)
   Call Enc28j60_writecontrolregbyte(erxrdptl , Enc28j60_value)
   Enc28j60_value = High(enc28j60_nextpacketptr)
   Call Enc28j60_writecontrolregbyte(erxrdpth , Enc28j60_value)
   'decrement the packet counter indicate we are done with this packet
   Enc28j60_value = 0
   Enc28j60_value.econ2_pktdec = 1
   Call Enc28j60_bitfield_set(econ2 , Enc28j60_value)
   'Set Led


    'Handle the packet
    If T_enetpackettype0 = &H08 Then
      If T_enetpackettype1 = &H06 Then                      'Type:ARP
         If T_arp_op0 = &H00 Then                           'ARP request
            If T_arp_op1 = &H01 Then                        'ARP request
              If T_arp_tipaddr0 = Myip(1) Then              'ARP for us
                If T_arp_tipaddr1 = Myip(2) Then
                   If T_arp_tipaddr2 = Myip(3) Then
                      If T_arp_tipaddr3 = Myip(4) Then
                        Call Arpreply
                      End If
                   End If
                End If
              End If
            End If
         End If
      End If
      If Buffer(14) = &H00 Then                             'Type:IP
         If Buffer(15) = &H45 Then                          'We handle only simple IP packets
            'If Buffer(21) = 0 Then                          'We handle only non fragmented packets
              If Buffer(31) = Myip(1) Then                  'Ip packet for us
                If Buffer(32) = Myip(2) Then
                   If Buffer(33) = Myip(3) Then
                      If Buffer(34) = Myip(4) Then
                        If T_ip_proto = 1 Then              'Protocol:ICMP
                           If Buffer(35) = &H08 Then        'ICMP echo request
                              Call Pingreply
                           End If
                        End If
                        'If T_ip_proto = 17 Then             'Protocol:UDP
                           'Call Udp_receive
                        'End If
                        If T_ip_proto = 6 Then              'Protocol:TCP
                           Call Tcp
                        End If
                      End If
                   End If
                End If
              'End If
            End If
         End If
      End If
    End If
End Sub


Sub Enc28j60_packetsend(pcktlen As Word)
   'Load packet into the ENC
   Enc28j60_cs = 0
   Spdr = Enc28j60_write_buf_mem
   Do
   Loop Until Spsr.spif0 = 1
   Spdr = &B000_1110                                        'per packet byte
   Do
   Loop Until Spsr.spif0 = 1
   For X = 1 To Pcktlen
      Spdr = Buffer(x)
      Do
      Loop Until Spsr.spif0 = 1
   Next X
   Enc28j60_cs = 1
   'Minimum packet length is 60
   If Pcktlen < 60 Then Pcktlen = 60
   'Reset transmit logic
   Enc28j60_value = 0
   Enc28j60_value.econ1_txrst = 1
   Call Enc28j60_bitfield_set(econ1 , Enc28j60_value)
   Call Enc28j60_bitfield_clear(econ1 , Enc28j60_value)
   'set the write pointer to start of transmit buffer area
   Enc28j60_value = Low(txstart_init)
   Call Enc28j60_writecontrolregbyte(ewrptl , Enc28j60_value)
   Enc28j60_value = High(txstart_init)
   Call Enc28j60_writecontrolregbyte(ewrpth , Enc28j60_value)
   'set the TXND pointer to correspond to the packet size given
   Enc28j60_value = Low(txstart_init)
   Enc28j60_value = Enc28j60_value + Low(pcktlen)
   Call Enc28j60_writecontrolregbyte(etxndl , Enc28j60_value)
   Enc28j60_value = High(txstart_init)
   Enc28j60_value = Enc28j60_value + High(pcktlen)
   Call Enc28j60_writecontrolregbyte(etxndh , Enc28j60_value)
   'write per-packet control byte has been put in the writeroutine
   'send the contents of the transmit buffer onto the network
   Enc28j60_value = 0
   Enc28j60_value.econ1_txrts = 1
   Call Enc28j60_bitfield_set(econ1 , Enc28j60_value)
End Sub


'***************** end of the ENC28J60-routines *******************************


Sub Arpreply
   'The original request packet is in the buffer, we just change some things
   'Swap MAC addresses
'   Call Src2dest
   'move hardware source address to destination address

   T_enetpacketdest0 = T_enetpacketsrc0
   T_enetpacketdest1 = T_enetpacketsrc1
   T_enetpacketdest2 = T_enetpacketsrc2
   T_enetpacketdest3 = T_enetpacketsrc3
   T_enetpacketdest4 = T_enetpacketsrc4
   T_enetpacketdest5 = T_enetpacketsrc5
   'Set source MAC in ethernet frame, pos 7

   'Call Src2mymac
   'Make ethernet module mac address the source address
   T_enetpacketsrc0 = Mymac(1)
   T_enetpacketsrc1 = Mymac(2)
   T_enetpacketsrc2 = Mymac(3)
   T_enetpacketsrc3 = Mymac(4)
   T_enetpacketsrc4 = Mymac(5)
   T_enetpacketsrc5 = Mymac(6)

   'Copy target MAC in ARP packet
   T_arp_dest_enetpacket0 = T_enetpacketdest0
   T_arp_dest_enetpacket1 = T_enetpacketdest1
   T_arp_dest_enetpacket2 = T_enetpacketdest2
   T_arp_dest_enetpacket3 = T_enetpacketdest3
   T_arp_dest_enetpacket4 = T_enetpacketdest4
   T_arp_dest_enetpacket5 = T_enetpacketdest5
   'Set target IP in ARP packet
   T_arp_tipaddr0 = T_arp_sipaddr0
   T_arp_tipaddr1 = T_arp_sipaddr1
   T_arp_tipaddr2 = T_arp_sipaddr2
   T_arp_tipaddr3 = T_arp_sipaddr3
   'Copy source MAC to ARP
   T_arp_src_enetpacket0 = T_enetpacketsrc0
   T_arp_src_enetpacket1 = T_enetpacketsrc1
   T_arp_src_enetpacket2 = T_enetpacketsrc2
   T_arp_src_enetpacket3 = T_enetpacketsrc3
   T_arp_src_enetpacket4 = T_enetpacketsrc4
   T_arp_src_enetpacket5 = T_enetpacketsrc5
   'Set source IP to ARP packet pos 29
   T_arp_sipaddr0 = Myip(1)
   T_arp_sipaddr1 = Myip(2)
   T_arp_sipaddr2 = Myip(3)
   T_arp_sipaddr3 = Myip(4)
   'Set ARP type from Request to Reply
   T_arp_op1 = 2
   'Send the reply packet
   Call Enc28j60_packetsend(42)
End Sub


Sub Pingreply
   'Local Packetlength As Word
   Packetlength = T_ip_pktlen0 * 256
   Packetlength = Packetlength + T_ip_pktlen1
   Packetlength = Packetlength + 13                         'We are going to calculate the checksum till the end of packet (IP length + 14 byte of the ethernet stuff), -1 to get word start
   'set echo reply
   T_icmp_type = &H00
   T_icmp_code = &H00
   'setup the IP-header
   Call Setipaddrs
   Call Icmp_checksum
   Packetlength = Packetlength + 1
   'Send the reply packet
   Call Enc28j60_packetsend(packetlength)
End Sub


Sub Setip_id
   Local Ip_id As Word
   T_id0 = High(ip_id)
   T_id1 = Low(ip_id)
   Ip_id = Ip_id + 1
End Sub


' Routine to calculate a IP-header checksum
'
Sub Ip_header_checksum
  Local Ip_checksum16 As Word
  Local Ip_header_length As Byte
  T_ip_hdr_cksum = &H00
  'Calculate IP header length
  Ip_header_length = T_ip_vers_len And &H0F
  Ip_header_length = 4 * Ip_header_length
  Ip_checksum16 = Tcpchecksum(buffer(15) , Ip_header_length )
  'Store the checksum value in the packet buffer
  T_ip_hdr_cksum1 = High(ip_checksum16)
  T_ip_hdr_cksum0 = Low(ip_checksum16)
End Sub


' Routine to calculate a ICMP-checksum
'
Sub Icmp_checksum
  Local I_header_length As Word
  'Clear the ICMP checksum before starting calculation
  T_icmp_cksum = &H00
  'Calculate the ICMP checksum
  I_header_length = T_ip_pktlen1 - 20
  I_checksum16 = Tcpchecksum(buffer(35) , I_header_length ) 'built-in way
  T_icmp_cksum1 = High(i_checksum16)
  T_icmp_cksum0 = Low(i_checksum16)
End Sub


' Routine to handle the source/destination address
'
Sub Setipaddrs
   T_ip_destaddr = T_ip_srcaddr
   'make ethernet module IP address source address
   T_ip_srcaddr = My_ip
   'move hardware source address to destination address
   T_enetpacketdest0 = T_enetpacketsrc0
   T_enetpacketdest1 = T_enetpacketsrc1
   T_enetpacketdest2 = T_enetpacketsrc2
   T_enetpacketdest3 = T_enetpacketsrc3
   T_enetpacketdest4 = T_enetpacketsrc4
   T_enetpacketdest5 = T_enetpacketsrc5
   'Set source MAC in ethernet frame, pos 7
   'Make ethernet module mac address the source address
   T_enetpacketsrc0 = Mymac(1)
   T_enetpacketsrc1 = Mymac(2)
   T_enetpacketsrc2 = Mymac(3)
   T_enetpacketsrc3 = Mymac(4)
   T_enetpacketsrc4 = Mymac(5)
   T_enetpacketsrc5 = Mymac(6)
'   Call Src2mymac
   Call Ip_header_checksum
End Sub


'Tcp-checksum
'
Sub Tcp_checksum
   Local Whulp1 As Word
   Local Tempword2 As Word
   Local Val1 As Word
   Local Val2 As Word
   Tcp_cksum = 0
   Call Srcdestchksum
   'resultaat in I_chksum32
   Tempwordh = T_ip_pktlen0
   Tempwordl = T_ip_pktlen1
   I_chksum32 = I_chksum32 + Tempword
   Tempword2 = T_ip_vers_len And &H0F
   Tempword2 = Tempword2 * 4
   I_chksum32 = I_chksum32 - Tempword2
   Whulp1 = Tempword - 20
   Val2 = Highw(i_chksum32)
   Val1 = I_chksum32
   I_checksum16 = Tcpchecksum(buffer(&H23) , Whulp1 , Val2 , Val1)
   Tcp_cksuml = High(i_checksum16)
   Tcp_cksumh = Low(i_checksum16)
End Sub


Sub Srcdestchksum
   'checksum TCP header
   I_chksum32 = 0
   I_value16h = T_ip_srcaddr0
   I_value16l = T_ip_srcaddr1
   I_chksum32 = I_chksum32 + I_value16
   I_value16h = T_ip_srcaddr2
   I_value16l = T_ip_srcaddr3
   I_chksum32 = I_chksum32 + I_value16
   I_value16h = T_ip_destaddr0
   I_value16l = T_ip_destaddr1
   I_chksum32 = I_chksum32 + I_value16
   I_value16h = T_ip_destaddr2
   I_value16l = T_ip_destaddr3
   I_chksum32 = I_chksum32 + I_value16
   'proto
   I_chksum32 = I_chksum32 + T_ip_proto
End Sub


' Telnet
'
Sub Telnet
   Local Work As Byte
   Local D As Byte
   Local Msg As String * 70
   Local Char As String * 1
   Local Work2 As Word
   Local Tcp_header_len As Byte
   Local Expected_seq As Long
   Work = Tcp_flags
   Tcp_fin = Work.0
   Tcp_syn = Work.1
   Tcp_rst = Work.2
   Tcp_psh = Work.3
   Tcp_ack = Work.4
   Tcp_urg = Work.5

   Packetlength = T_ip_pktlen0 * 256
   Packetlength = Packetlength + T_ip_pktlen1
   Packetlength = Packetlength - 40

   Acknum3 = Tcp_acknum0
   Acknum2 = Tcp_acknum1
   Acknum1 = Tcp_acknum2
   Acknum0 = Tcp_acknum3

   Seqnum3 = Tcp_seqnum0
   Seqnum2 = Tcp_seqnum1
   Seqnum1 = Tcp_seqnum2
   Seqnum0 = Tcp_seqnum3

   Tcp_header_len = Tcp_hdr And &HF0
   Shift Tcp_header_len , Right , 4
   Tcp_header_len = Tcp_header_len * 4

   Call Ack2tcp_ack
   Call Seq2tcp_seq

   'if an ACK is received and the destination port address is valid
   'and no data is in the packet
   If Tcp_ack = 1 Then
      If Tcp_psh = 0 Then
         If Synflag = 1 Then

            Synflag = 0
            Expected_seq = Acknum
            Acknum = Seqnum + Packetlength
            Seqnum = Expected_seq
            Call Ack2tcp_ack
            Call Seq2tcp_seq
            Call Swapdestport2srcport
            Call Swapsrc2dest
            'Move IP source address to destination address
            Swap T_ip_destaddr , T_ip_srcaddr
            Tcp_flags = 0
            Set Tcp_flags._ack

            Msg = "TuxGraphics{010}{010}{010}{013}"
            Msg = Msg + "1. Info{010}{010}{013}"
            Msg = Msg + "2. Option B{010}{010}{013}"
            Msg = Msg + "3. Option C{010}{010}{013}"
            Msg = Msg + "4. Quit{010}{013}{010}{010}"
            For Work = 1 To Len(msg)
                D = 54 + Work
                Char = Mid(msg , Work , 1)
                Buffer(d) = Asc(char)
            Next Work
            D = Len(msg)
            Packetlength = 40 + D
            T_ip_pktlen0 = High(packetlength)
            T_ip_pktlen1 = Low(packetlength)
            Call Ip_header_checksum
            Call Tcp_checksum
            Packetlength = Packetlength + 20
            Call Enc28j60_packetsend(packetlength)
         End If
      End If
   End If



   'if an ACK is received and the port address is valid and there is
   'data in the incoming packet
   If Tcp_ack = 1 Then
      If Tcp_psh = 1 Then
         If Packetlength > 0 Then
            Expected_seq = Acknum
            Acknum = Seqnum + Packetlength
            Seqnum = Expected_seq
            Call Ack2tcp_ack
            Call Seq2tcp_seq
            Call Swapdestport2srcport
            Call Swapsrc2dest
            'Move IP source address to destination address
            Swap T_ip_destaddr , T_ip_srcaddr
            Tcp_flags = 0
            Set Tcp_flags._ack

            'Here the choices
            Select Case Buffer(55)
                   Case 49 : Call Optiona
                   Case 50 : Call Optionb
                   Case 51 : Call Optionc
                   Case 52 : Call Optionquit
            End Select

            Packetlength = Packetlength + 40
            T_ip_pktlen0 = High(packetlength)
            T_ip_pktlen1 = Low(packetlength)
            Call Ip_header_checksum
            Call Tcp_checksum
            Packetlength = Packetlength + 20
            Call Enc28j60_packetsend(packetlength)

         End If
      End If
   End If


   'this code segment processes the incoming SYN from the Telnet client
   'and sends back the initial sequence number (ISN) and acknowledges
   'the incoming SYN packet
   If Tcp_syn = 1 Then
      Acknum = Seqnum + 1
      Seqnum = &H1011FFFF                                   'Initial Sequence Number
      Set Synflag

      Call Ack2tcp_ack
      Call Seq2tcp_seq

      Call Swapdestport2srcport
      Call Swapsrc2dest
      'Move IP source address to destination address
      Swap T_ip_destaddr , T_ip_srcaddr
      Tcp_flags = 0
      Set Tcp_flags.syn
      Set Tcp_flags._ack
      T_ip_pktlen0 = &H00
      T_ip_pktlen1 = 48
      Call Ip_header_checksum
      Call Tcp_checksum
      Call Enc28j60_packetsend(62)
    End If


    'if ACK and FIN
    If Tcp_ack = 1 Then
       If Tcp_fin = 1 Then
          'end the session
          'Print "TCP_ACK en TCP_FIN"
       End If
    End If
End Sub


' TCP
'
Sub Tcp
   If Tcp_destporth = 0 Then
       Select Case Tcp_destportl
              'Case 80 : Call Http
              Case 23 : Call Telnet
       End Select
   End If
End Sub


Sub Ack2tcp_ack
   Tcp_acknum3 = Acknum0
   Tcp_acknum2 = Acknum1
   Tcp_acknum1 = Acknum2
   Tcp_acknum0 = Acknum3
End Sub


Sub Seq2tcp_seq
   Tcp_seqnum3 = Seqnum0
   Tcp_seqnum2 = Seqnum1
   Tcp_seqnum1 = Seqnum2
   Tcp_seqnum0 = Seqnum3
End Sub


Sub Swapsrc2dest
   Swap T_enetpacketdest0 , T_enetpacketsrc0
   Swap T_enetpacketdest1 , T_enetpacketsrc1
   Swap T_enetpacketdest2 , T_enetpacketsrc2
   Swap T_enetpacketdest3 , T_enetpacketsrc3
   Swap T_enetpacketdest4 , T_enetpacketsrc4
   Swap T_enetpacketdest5 , T_enetpacketsrc5
End Sub


Sub Swapdestport2srcport
    Swap Tcp_srcporth , Tcp_destporth
    Swap Tcp_srcportl , Tcp_destportl
End Sub


Sub Optiona
   Local Msg As String * 70
   Local Work As Byte
   Local D As Byte
   Local Char As String * 1
   Local Pointer As Word
   Msg = "{013}{010}Info pressed{013}{010}"
   Pointer = 54
   For Work = 1 To Len(msg)
       D = Pointer + Work
       Char = Mid(msg , Work , 1)
       Buffer(d) = Asc(char)
   Next Work
   Pointer = Pointer + Len(msg)
   Packetlength = Len(msg)

   Msg = "IP-nr.      " + Str(myip(1))
   Msg = Msg + "." + Str(myip(2))
   Msg = Msg + "." + Str(myip(3))
   Msg = Msg + "." + Str(myip(4))
   Msg = Msg + "{013}{010}"

   For Work = 1 To Len(msg)
       D = Pointer + Work
       Char = Mid(msg , Work , 1)
       Buffer(d) = Asc(char)
   Next Work
   Pointer = Pointer + Len(msg)
   Packetlength = Packetlength + Len(msg)

   Msg = "MAC-address " + Hex(mymac(1)) + "-" + Hex(mymac(2)) + "-" + Hex(mymac(3)) + "-"
   Msg = Msg + Hex(mymac(4)) + "-" + Hex(mymac(5)) + "-" + Hex(mymac(6)) + "{013}{010}"
   For Work = 1 To Len(msg)
       D = Pointer + Work
       Char = Mid(msg , Work , 1)
       Buffer(d) = Asc(char)
   Next Work
   Pointer = Pointer + Len(msg)
   Packetlength = Packetlength + Len(msg)


End Sub


Sub Optionb
   Local Msg As String * 25
   Local Work As Byte
   Local D As Byte
   Local Char As String * 1
   Msg = "{013}{010}Option B pressed{013}{010}"
   For Work = 1 To Len(msg)
       D = 54 + Work
       Char = Mid(msg , Work , 1)
       Buffer(d) = Asc(char)
   Next Work
   Packetlength = Len(msg)
End Sub


Sub Optionc
   Local Msg As String * 25
   Local Work As Byte
   Local D As Byte
   Local Char As String * 1
   Msg = "{013}{010}Option C pressed{013}{010}"
   For Work = 1 To Len(msg)
       D = 54 + Work
       Char = Mid(msg , Work , 1)
       Buffer(d) = Asc(char)
   Next Work
   Packetlength = Len(msg)
End Sub


Sub Optionquit
   Local Msg As String * 70
   Local Work As Byte
   Local D As Byte
   Local Char As String * 1
   Msg = "{013}{010}{010}Connection closed - Bye{013}{010}"
   For Work = 1 To Len(msg)
       D = 54 + Work
       Char = Mid(msg , Work , 1)
       Buffer(d) = Asc(char)
   Next Work
   Set Tcp_flags.fin
   Set Tcp_flags.psh
   Packetlength = Len(msg)
End Sub