Sometimes AT+CIPSEND command cannot wait for SEND OK

[twcczhang]

Hi,

I try to use NUMAKER-PFM-M487 + ESP8266 to run mbed client application, but sometimes the application works well, sometimes it works fail. I find in fail cases, the root cause is the CIPSEND AT command can only receive "Recv xx bytes" message, but never wait for "SEND OK" message.

In below log, the "AT? XXX" means the program is waiting for XXX, and "AT= XXX" means the program already get XXX message. You can see the first 643 bytes is send ok, but the second 75 bytes is send fail. In mbed, the default timeout of ESP8266 is 2 second. After increase the timeout to 5 second and 10 second, the program still cannot wait for "SEND OK" message from ESP8266.

......
[2018-08-15 11:42:36.504] AT> AT+CIPSEND=0,643
[2018-08-15 11:42:36.505] &1, > (0x3e)
[2018-08-15 11:42:36.505] AT? >%n
[2018-08-15 11:42:36.505] AT< AT+CIPSEND=0,643
[2018-08-15 11:42:36.506] AT< OK
[2018-08-15 11:42:36.514] AT= >
[2018-08-15 11:42:36.514] &2
[2018-08-15 11:42:36.540] &1, S (0x53)
[2018-08-15 11:42:36.541] AT? SEND OK
[2018-08-15 11:42:36.542] %n
[2018-08-15 11:42:36.562] AT<
[2018-08-15 11:42:36.564] AT< Recv 643 bytes
[2018-08-15 11:42:36.832] AT= SEND OK
[2018-08-15 11:42:36.835]
[2018-08-15 11:42:36.835] &2
[2018-08-15 11:42:38.978] Simulated button clicked 1 times
[2018-08-15 11:42:39.090] AT> AT+CIPSEND=0,75
[2018-08-15 11:42:39.091] &1, > (0x3e)
[2018-08-15 11:42:39.091] AT? >%n
[2018-08-15 11:42:39.091] AT< AT+CIPSEND=0,75
[2018-08-15 11:42:39.091] AT< OK
[2018-08-15 11:42:39.092] AT= >
[2018-08-15 11:42:39.099] &2
[2018-08-15 11:42:39.104] &1, S (0x53)
[2018-08-15 11:42:39.104] AT? SEND OK
[2018-08-15 11:42:39.104] %n
[2018-08-15 11:42:39.104] AT<
[2018-08-15 11:42:39.104] AT< Recv 75 bytes
[2018-08-15 11:42:41.109] AT(Timeout)
[2018-08-15 11:42:41.111] SEND command is still not finished !!
......

Please help to clarify and fix this issue. Thanks.

BR,
twcczhang

[Her Mary]

Maybe due to the bad network, you can capture WiFi packets by wireshark to find out it.