I am using SARA-R410M-02B to access a remote server via ppp link. Settings:
- SARA-R4 DTR pin connected to ground.
- SIM card working well with 4G, CAT M1
There is a problem with the IPCP layer when the SMS command is used before ppp link is established.
The traffic is like this:
AT+CCLK? +CCLK: "18/11/08,03:28:37"
AT+CSQ +CSQ: 16,99
AT+CMGS="0449598788" > Logger Message from unit 10801688, site ID: <None>, Signal Strength(0-100):51;.
ATD*99# CONNECT 150000000
followed with some legal bytes for LCP and PAP, all correct. Then the system hits the IPCP layer.
The IPCP request packet is sent out properly. It is FF 03 80 21 01 09 00 0A 03 06. There is no response from the remote site for the request. The system keeps waiting until timeout and the ppp link dropped.
When CMGS command is not used, there is no SMS, the IPCP layer works well. There is no ppp link drop.
Why the SMS service is affecting the IPCP layer instead of LCP or PAP?
What could be the cause?
Thanks for your kind assistance.