Re: [lwip-users] Opinions on using lwIP for making application GPRS-chipset-agnostic

[Ajay Garg]

Thanks Sergio for the reply.

On Fri, Aug 21, 2015 at 5:46 PM, Sergio R. Caprile <address@hidden> wrote:

What I would do, if I were in your shoes, is to write my app for lwIP,
and then either use PPP for those TCP/IP capable GPRS modules

You mean even if we use lwIP, we would be dependent on the TCP/IP (stack) of the GPRS module?

That would defeat the purpose of using lwIP at the first place.

I am sure I am having a massive misunderstanding ..

 

and a
layer-2 interface (netif) for the other ones.
This way, your app is always the same and you only change code for what
is below layer-3. You'll have to write your own netif, though.
lwIP is a TCP/IP stack which communicates to "the outside world" via
interfaces called "netif". Basically you can run it on top of everything
where you can write a netif for.

I went through http://lwip.wikia.com/wiki/PPP

We majorly need to code the "read" and "write" methods, right?

In our case, if we are interfacing the GPRS-module with the Micro-controller via UART, then this would mean simply reading-from / writing-to UART, right?

Also, one another question (this is majorly due to my lack of understanding of nitty-gritties of the protocols) ::

For using TCP/IP/PPP/Serial, we simply have to bring the GPRS-Module into "Connect OK" mode (by using primitive AT commands). Thereafter, we need to switch the GPRS-module into "data mode" and then leave it to lwIP to set up the TCP/IP contexts, and later allow the usage of sockets.

Is my understanding of the algorithm (at a broader level) correct?

Once again, thanks a ton to both Sylvain and Sergio for the replies. I am heartly grateful.

Thanks and Regards,

Ajay

 

The git HEAD contains working PPP code, stable 1.4.1 is OK for
everything else but PPP and IPv6, although the maintainers recommend
using git HEAD now because 1.5.0 is just around the corner.
Your app will be written for lwIP using one of several APIs available.
The 'RAW' API, a poem for bare metal lovers; 'netconn' API, more
suitable for RTOS accolites; and 'socket' API for the full-OS minds.
Pick your own, and please, read the wiki
http://lwip.wikia.com/

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Regards,
Ajay