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Kieran
Joined: 28 Nov 2003
Posts: 39
Location: Essex UK
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| EDTP Packet Whacker UDP transmit problems |
 Posted: Fri Nov 05, 2004 3:23 am |
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Edited and reposted as a new thread
EDTP Packet Whacker (RTL8019AS)
I have one of these hooked up to a 18F452 and have all the demo programs running.
I want to extend the UDP features and I am stuck.
I am trying to send a string back to a PC with the following
triggered by an incomming UDP message from the PC.
Src and Dest are derived from the incoming message.
| Code: |
byte dat_buff[128];
// Src source PORT
// Dest PORT
// *dat string to send
send_UDP(int16 Src, int16 Dest, byte *dat)
{
memset(&packet[UDP_data],0,50); // Flush UDP data section of packet
txlen = strlen(dat) + 8; // UDP data + header len
ip_packet_len = 20 + txlen; // Allow for IP header
// Set IP header up
packet[ip_pktlen] = make8(ip_packet_len,1);
packet[ip_pktlen+1] = make8(ip_packet_len,0);
setipaddrs();
// UDP header
packet[UDP_srcport] = make8(Src,1);
packet[UDP_srcport + 1] = Src;
packet[UDP_destport] = make8(Dest,1);
packet[UDP_destport + 1] = Dest;
txlen = strlen(dat) + 8; // UDP data + header len
printf("send %s len %ld\r",dat,txlen);
packet[UDP_len] = make8(txlen,1); // Should be 0 - buffer size
packet[UDP_len + 1] = txlen;
// Write data to packet
strcpy(&packet[UDP_data],dat);
//calculate the UDP checksum
packet[UDP_cksum] = 0x00;
packet[UDP_cksum+1] = 0x00;
hdr_chksum =0;
hdrlen = 0x08;
addr = &packet[ip_srcaddr];
cksum();
hdr_chksum = hdr_chksum + packet[ip_proto];
hdrlen = 0x02;
addr = &packet[UDP_len];
cksum();
hdrlen = make16(packet[UDP_len],packet[UDP_len+1]);
addr = &packet[UDP_srcport];
cksum();
chksum16= ~(hdr_chksum + ((hdr_chksum & 0xFFFF0000) >> 16));
packet[UDP_cksum] = make8(chksum16,1);
packet[UDP_cksum+1] = make8(chksum16,0);
// Calculate length and send
txlen = ip_packet_len + 14; // total packet len
if(txlen < 60)
txlen = 60;
dump_header();
show_packet();
data_L = make8(txlen,0);
data_H = make8(txlen,1);
// Data to RTL8019
write_creg(CR,0x22);
write_creg(TPSR,txstart);
write_creg(RSAR0,0x00);
write_creg(RSAR1,0x40);
write_creg(ISR,0xFF);
write_creg(RBCR0,data_L);
write_creg(RBCR1,data_H);
write_creg(CR,0x12);
for(i=0;i<(txlen);++i)
write_creg(RDMAPORT,packet[enetpacketDest0+i]);
byte_read = 0;
while(!bit_test(byte_read,RDC))
read_creg(ISR);
write_creg(TBCR0,txlen - 4);
write_creg(TBCR1,make8(txlen,1));
write_creg(RBCR0,data_L);
write_creg(RBCR1,data_H);
write_creg(CR,0x24);
}
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Calls and variables are from the packet whacker code.
If I replace the code from below the checksum with the Packet Whacker echo_packet() function then all is well. Any ideas?
Kieran |
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Douglas Kennedy
Joined: 07 Sep 2003
Posts: 755
Location: Florida
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| Posted: Fri Nov 05, 2004 7:00 am |
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| The packet is probably malformed...Install on the PC in your network a packet sniffer ( ethereal ...free download from the web). It will show you the error in the packet you are sending assuming the packet makes it out onto the ethernet link. Once you know the error eg. checksum you can work back from there into your code. It's a bit more work than just pouring over your code but the packet snifer will catch intermittent issues that you might encounter going forward and is a very useful tool. |
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Kieran
Joined: 28 Nov 2003
Posts: 39
Location: Essex UK
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| Posted: Fri Nov 05, 2004 2:30 pm |
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Fixed
| Code: |
write_creg(TBCR0,txlen - 4);
write_creg(TBCR1,make8(txlen,1));
write_creg(RBCR0,data_L);
write_creg(RBCR1,data_H);
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Replaced by
| Code: |
write_creg(TBCR0,data_L);
write_creg(TBCR1,data_H);
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Whoops - over ambitious cut and paste!
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