W5100 is sending garbage data

Question

Hi, It is obviously some configuration issue, but I cannot figure out what is the problem. I start the socket as a TCP server and I can connect from client normally. But when I try to send one char from server to client, client receives some garbage stream. I have set: tx mem size (0x001B) as 0x55 (2kb per socket) tx write pointer 0x0424 = 0x40 0x0425 = 0x00 when sending a char i first read the txWritePtr, one example is: 0x0424 => 0xD8 0x0425 => 0x90 Then i mask the pointer with 0x7ff and add to base addess 0x4000, which gives me address of 0x4090 on which I sent one character. And after I update txWritePtr with new address 0x0424 = 0x40 0x0425 = 0x91 And of course send the Send command to command register. After that I receive quite amount of garbage (I dont really know how much characters I receive)… I am sure it is some obvious mistake I am making, but longer I read the datasheet and look at the code, less I have ideas what could be the issue… Thanks in advance.

irinakim · Answer

HI~ gossamer If you use the Socket0(allow the 2kb : tx size of socket0), socket0 have tx mem size as 0x4000~ 0x47FF. And when socket connection is complete, S0_TX_WR value has random value in 0x4000~0x47FF. It transmits data from current S0_TX_RR to S0_TX_WR and automatically changes after transmission is finished(After send command is completed and S0_IR(SEND_OK) is enable). And if total TCP packet is less then 60byte, W5100 send 60byte packet including garbage data(padding data). You need to confirm. Best regards, irina

gossamer · Answer

Yeah, I am not talking about padding data. This is like dumping of full buffer before posting the data I have sent. Yes, I get random value of TX_WR and TX_RR is 0. Which means that every time it will send 0->TX_WR + my data ? For example, TX_WR = 1000; my data is 24 bytes long, first time I initiate send it will send 1024 bytes, every other send is OK, it will just send 24 bytes. Do I need to set the RR before writing to tx buffer ?

Eugeny · Answer

gossamer: 0x0424 => 0xD8 0x0425 => 0x90 [quote=“gossamer”]0x0424 = 0x40 0x0425 = 0x91[/quote] If you use all 16 bits updating the pointer, will that work for you? Thus pointer before you issue SEND command, when sending one char, will be: 0x0424 = 0xD8 0x0425 = 0x91 It sounds logical that you get long stream of garbage. In your case size of calculated data 4091-d890=6801 (26 625 bytes).

gossamer · Answer

Nice ! That was exactly the issue. Writing value on 0x4090, but setting txWritePtr to 0xD891 after writing one character. To be honest datasheet was so vague on this detail, that i would never figure it out Thanks Eugeny.