[lwip-users] PPPoSerial and 4G modem

[Giuseppe Modugno]

I'm trying to make a data connection with a 4G modem from SIMCOM (A7672E).

After AT+CGDATA=... and ATD*99#, the modem replies with CONNECT and 
enters in online data state.

Now I'm ready to launch lwip app configured to use PPPoSerial and 
sntp_example (just to understand if the full stack is operating). I'm 
using last lwip commit and building in Windows with mingw compiler. At 
the end you'll find the log.

As you can see, PPP connection is established, but with the warning 
Could not determine remote IP address: defaulting to 10.64.64.64.
I don't know if this warning is important or not.

Moreover, PPP callback doesn't show any DNS configured for netif, but 
PPP subsystem shows two DNS servers afterward.

Another thing is the message udp_send: No route to 93.94.88.50. 
(93.94.88.50 should be the IP address of pool.ntp.org, one of available 
SNTP server). In this case I suspect PPP hadn't configured the netif 
with the correct gateway.

Even if I set the SNTP server name, the DNS subsystem complains because 
no DNS server is configured.


$ .\example_app.exe 6
Using serial port 6 for PPP
ppp_connect: COM6
sio_open: file "\\.\COM6" (6) successfully opened: 0x000001d8
ppp phase changed[1]: phase=0
ppp_connect[1]: holdoff=0
ppp phase changed[1]: phase=3
pppos_connect: unit 1: connecting
ppp_start[1]
ppp phase changed[1]: phase=6
ppp_send_config[1]
pppos_send_config[1]: out_accm=FF FF FF FF
ppp_recv_config[1]
pppos_recv_config[1]: in_accm=FF FF FF FF
ppp: auth protocols: PAP=1 CHAP=1 CHAP_MD5=1
pppos_write[1]: len=24
ppp_start[1]: finished
sntp_init: SNTP initialised
sntp_request: current server address is 93.94.88.50
sntp_send_request: Sending request to server
udp_send
udp_send: No route to 93.94.88.50
pppos_write[1]: len=24
pppos_input[1]: got 96 bytes
pppos_write[1]: len=28
ppp_netif_set_mtu[1]: mtu=1500
ppp_send_config[1]
pppos_send_config[1]: out_accm=0 0 0 0
ppp_recv_config[1]
pppos_recv_config[1]: in_accm=0 0 0 0
ppp phase changed[1]: phase=7
pppos_write[1]: len=19
pppos_input[1]: got 12 bytes
PAP authentication succeeded
ppp phase changed[1]: phase=9
pppos_write[1]: len=14
pppos_input[1]: got 38 bytes
pppos_write[1]: len=14
pppos_write[1]: len=26
pppos_input[1]: got 38 bytes
pppos_write[1]: len=8
Could not determine remote IP address: defaulting to 10.64.64.64
sifup[1]: err_code=0
pppLinkStatusCallback: PPPERR_NONE
   our_ipaddr  = 10.10.245.68
   his_ipaddr  = 10.64.64.64
   netmask     = 255.255.255.255
   dns1        = 0.0.0.0
   dns2        = 0.0.0.0
local  IP address 10.10.245.68
remote IP address 10.64.64.64
primary   DNS address 10.133.18.210
secondary DNS address 10.132.100.181
ppp phase changed[1]: phase=10
sntp_retry: Next request will be sent in 15000 ms
sntp_request: current server address is 93.94.88.50
sntp_send_request: Sending request to server
udp_send
udp_send: No route to 93.94.88.50