I am using the HL7692 and PPP.
The module is automatically selecting 2G instead of 4G, presumable due to signal levels.
In this case (using my Keil TCP/IP stack) I can send ATDT99**1# to start my PPP connection, negotiate the connection OK and transfer data etc OK. It all works OK.
If I then force the module to select 4G (AT+KSRAT=5) then the unit registers with 4G ok. However, when I initiate a PPP connection, the connection negotiation fails with Conf_Rej IP Address Rejected.
Any ideas on why this could be? Could it be caused by a low 4G signal or is it because my stack only supports IPv4 - perhaps 2G works with IPv4 but 4G only works with IPv6?