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PPP experience?



Does any of you have experience in the usage of the PPP library. I am going to attack it soon, and wanted to know if there is trouble ahead?


If the underlying handling of the TCP/IP is good then there is not a lot you need to do with the PPP library to get it working. If you are familiar with sockets then once you do the connect call, you just go ahead and use sockets to do all your work.

One of the issues you may run into is the authentication method. 2 types are supported. PAP and CHAP. Normally you just leave this and the PPP driver should work out what the other end wants to work with but you may in some cases have to force this. It all depends on the network you are connecting to. I just put in an option to select this or leave in auto. That way I can sort out without having to do any new programme update for the client.

The PPP driver lacks actually setting the APN and doing the actual dialing so you need to do this yourself with AT commands. Once you get back the CONNECT from the modem with the ATD99**1# command you then call the PPP connect. You must keep the serial port open when you call it.

I suggest you also do AT commands to check for signal (AT+CSQ?) and network registration (AT+CREG?) before you do the dial command. The REG command is important after booting up the modem as you need to registered on the network prior to making the call to connect.

Post back here if you have any questions. I’ve done heaps of PPP stuff with various embedded systems including getting a driver working under Android.


@ Dave - thanks again for valuable input. Will start testing.


@ Dave McLaughlin -

What hardware are you using?


G400 and G120 with a custom modem board using the SIM900 module.

For the Android system I use the Olimex A20 with a custom board.