9 years ago.

3G Modem and LwIP

Hi MBED folks,

I'm working on a small board I designed (for the MBED-LPC1768) which is basically just some peripherals (Accelerometer & USB) and a 1A power. On the USB port I'm plugging a 3G dongle (Huawei E372) which is perfectly detected and the Serial Streams are greatly created (I can send and receive AT Commands).

Now when I try to hook up the LwIP stuffs, nothing is behaving like I expect and I really hope someone have a clue about resolving this issue.

• What I see is the execution freezing in the middle of "somewhere" (no blue led of the death).

[USB_DBG: /src/Pyrn3GModem/PPPIPInterface.cpp:134]Trying to connect with PPP
[USB_DBG: /src/Pyrn3GModem/ATCommandsInterface.cpp:268]Trying to read a new line from stream
[USB_DBG: /src/Pyrn3GModem/PPPIPInterface.cpp:63]LwIP: Init Stack
[USB_DBG: /src/Pyrn3GModem/USBSerialStream.cpp:81]Waiting for data availability -1 ms (-1 is infinite)
[USB_DBG: /src/Pyrn3GModem/PPPIPInterface.cpp:65]LwIP: Wait for setup
[USB_DBG: /src/Pyrn3GModem/PPPIPInterface.cpp:68]LwIP: setup done
[USB_DBG: /src/Pyrn3GModem/USBSe // <<=== Middle of somewhere 

• I can notice the RAM Usage is quite high 82%. I don't really know how this info is computed but something near 100% usage is alarming me (code static analysis??).

• When I reduce LwIP features (disabling DNS for instance) it goes further => To dialing. But unfortunately stops when the ppp writes/reads begins (sio_write/read).
• I'm Using http://developer.mbed.org/users/donatien/code/lwip_ppp_ethernet/ LwIP implementation.
• The PPP interface is fully inspired from http://developer.mbed.org/users/mbed_official/code/VodafoneUSBModem/.
• The 1A power does not seems to be causing the issue here.

Now, since tweeking the LwIP opts and disabling some features allows the code to run a little longer. I suspect missing RAM or something like that (maybe some threads requering memory for stack usage). Furthermore I could not find some option that greatly decrease the estimated RAM usage (always about 80->90%). Do you think I'm going in the right direction? Any idea of how can I track this weird bug?

Thank you very much for your time,

Regards, Clément