lwIP CMSIS port

This library is a dependency of lwip.

To use this port your application must provide user_lwipopts.h which contains optional user overrides of lwIP options. You can do this by adding an include directory to library lwipopts.

target_include_directories(lwipopts
    INTERFACE
        <PATH TO USER CONFIG>
)

You may use the template provided in ./include/user-config. See lwipopts.h in the lwIP project for details on options.

The lwipcore library requires a valid config to build. To use the configuration defined by this port, the application must link lwipcore to the lwip-cmsis-port.

target_link_libraries(lwipcore
    PRIVATE
        lwip-cmsis-port
)

Optionally, if you want to get tracing from lwIP you must provide a definition of DEBUG_PRINT in lwipopts library. For example a DEBUG_PRINT=printf will allow you to use the printf from libc whose stdio is retargeted to CMSIS Driver's serial by iotsdk-serial-retarget. You may do this like so:

target_link_libraries(my-application
    PRIVATE
        iotsdk-serial-retarget
)

target_compile_definitions(lwipopts
    INTERFACE
        DEBUG_PRINT=printf
)

EMAC Interface

The library requires an implementation of an MCU Driver HAL EMAC interface. The EMAC interface is retrieved using the function:

mdh_emac_t *mdh_emac_get_default_instance(void)

This function must be provided by the application.

Packet latency on the input interface

Normally the TCP/IP thread priority is higher than the thread servicing the interface receiving network packets. This optimises for heap memory consumption - any packets received are processed immediately to free up the buffer as quickly as we can. This might mean that the network interface is in the meantime buffering up data.

To prioritize servicing the input thread, link the lwip-cmsis-port CMake target with lwip-cmsis-port-low-input-latency as follows:

target_link_libraries(lwip-cmsis-port PUBLIC lwip-cmsis-port-low-input-latency)

If you use this option it's important to make sure the heap is big enough to buffer up all the data it receives. Dropped packets could be an indication of insufficent heap space. Enable LWIP debug prints in your user_lwipopts.h as shown below to see if pbuf allocations fail.

#define LWIP_DEBUG
#define PBUF_DEBUG LWIP_DBG_ON

License

Files are licensed under the Apache 2.0 license.