Hi!
I'm working with FreeRTOS v7.0.1 and LwIP 1.4.0 and I'm facing the following problem:
Device A and B transmit data every 40 ms to my board (where I'm running LwIP) and once in a while I can notice some data from device A is being missed.
So I did some research with CommView and found that:
1) Device A sends data (9 bytes length) to my board and get correct ACK from it:
| Sequence: 0x13D5388C (332740748)
|
| Acknowledgement:
0x00001A57 (6743) |
Response from my board:
| Sequence: 0x00001A57 (6743) |
|
| Acknowledgement:
0x13D53895 (332740757) |
2) Device A send 9-bytes data to my board, but this won´t ACK:
| Sequence: 0x13D5389E (332740766) |
| Acknowledgement:
0x00001A57 (6743) |
| Sequence: 0x00001A57 (6743) |
|
| Acknowledgement:
0x13D5389E (332740766) |
3)Device A does not care about it (maybe because data is already in ethernet transceiver buffer) and sends a new data (9-bytes); my board will not ACK it:
| Sequence: 0x13D538A7 (332740775) |
| Acknowledgement:
0x00001A57 (6743) |
| Sequence: 0x00001A57 (6743) |
|
Acknowledgement:
0x13D5389E (332740766)
4)Same as 3
| Sequence: 0x13D538B0 (332740784) |
| Acknowledgement:
0x00001A57 (6743) |
| Sequence: 0x00001A57 (6743) |
|
| Acknowledgement:
0x13D5389E (332740766) |
|
5) Same as 3
| Sequence: 0x13D538B9 (332740793) |
| Acknowledgement:
0x00001A57 (6743) |
| Sequence: 0x00001A57 (6743) |
|
| Acknowledgement:
0x13D5389E (332740766) |
6) Finally, device A is aware of the problem and retransmits data, but instead of transmitting 36 bytes (9 x 4), only transmits 18 bytes
| Sequence: 0x13D5389E (332740766) |
| Acknowledgement:
0x00001A57 (6743) |
And my board running Lwip 1.4.0 will acknowledge 36 bytes instead of 18:
| Sequence: 0x00001A57 (6743) |
|
Acknowledgement:
0x13D538C2 (332740802)
|
So device A won´t transmit last two 9-bytes packets, and they will be lost!
Anyone can help me with this? Is it a bug in LwIP or what is happening?
Thank you!