PPP Stack

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  • After lengthy experimentation with the SIM800 / SIM900 modules, I hit a wall in what the built-in TCPIP capabilities are able to provide. My goal is to connect to the AWS IoT service (MQTT and TLS) over GSM/GPRS.

    I think what needs to happen is to use the SIM dial-up command (ATD*99#) along with a ppp / tcpip stack (and the existing TLS layer).

    Am I missing something that would already do what I'm trying to accomplish? If not, what is the possibility of this being incorporated into the Espruino core? I've been looking at the lwIP/PPP stack as reference, but wanted to check in before going to far down this road.

    On a side note: I discovered the SIM modules provide a FAT file system over AT API. They appear to have over a MB of storage that can be used - a nice feature to have available if you want to store things like ssl certificates and are low on flash space.

  • That's a shame - what's the problem with TCP/IP on them? Could it just be that something needs escaping/unescaping? Have you updated the SIM900 firmware? I'd have thought that if there was a TCP/IP problem it's something that SIMcom would be very interested in fixing.

    There's nothing built-in for TCP/IP at the moment, but getting LwIP into Espruino would be very cool - it'd do things like allowing support for STM32s with Ethernet on-chip, and also perhaps IPv6 over BLE.

    Impressive about the filesystem too - I had no idea.

  • Hi Everybody,

    I am new to TCP and TLS. In my project I should get connected to AWS IoT server using MQTT and TLS over GPRS. I am using SIM5320 and STM32F4. Is it possible to implement TLS on SIM5230.

  • I haven't used SIM5230, but if it supports communication like the SIM900 then yes, it should work.

    It all depends on the available RAM though - are you using the Espruino Pico? If so you should be fine (as long as the certificates are in ROM). If you're doing some custom solution it depends what you use - but if you want me to help with that you'll have to pay consultancy... I can't afford to design your product for you for free :)

  • Hi Gordon,

    Thanks for your quick reply!

    SIM5230 communication is similar to SIM900. I am using TCP transporter mode.

    I never used Espruino Pico But STM32f407 has 1MB ROM and 192KB RAM. I am planning to use PolarSSL. If any better library is in marker please suggest me.

  • Assuming you tweak the build to include it, Espruino already includes mbedSSL so it should 'just work'...

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PPP Stack

Posted by Avatar for lukevanhorn @lukevanhorn

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