W5500 TCP - write to TX buffer before connection up

Question

Hi I am using the W5500 in a new design and it is working well. To send data over TCP I currently: Open a TCP socket Wait for the connection to come active Write to the TX buffer Issue a SEND command This works fine but I would like to change the order to: Open a TCP socket Write to the TX buffer Wait for the connection to come active Issue a SEND command When I tried this it did not work. Is there a way of writing to the TX buffer before the TCP connection is active? Bill

Coccoliso · Answer

The socket has to be connected. You can not fill the TX buffer of a disconnected socket because you do not know in which location write … the two TX buffer pointers are updated only upon connection.

billbgarland · Answer

Hi Coccoliso Can I do this: Open a TCP socket Write message to FIFO and save TX_WR pointers Wait for the connection to come active Modify TX_RD and TX_WR pointers to point to message in FIFO Issue a SEND command The reason I want to do this is that my host has very little RAM and I want to save my message in the W5500 FIFO.

Coccoliso · Answer

I do not remember the post but I’m pretty sure that the pointers contain 0 after reset but during the operations of opening of the socket containing two identical random values that are overwritten to the connection with the real value so I do not think that will work. The buffers are used as random-access memory as long as the socket is connected.