April 16, 2019 posted by

When executing correctly the demo application will behave as follows: In this case set pvData to the the address of the network buffer descriptor. While is is a simple robust technique – it is not efficient. Interrupt service routines In the demo application the vector table remains in flash. On the negative side, lwIP is undeniably quite complex to use at first, but time invested in its use will pay dividends in future projects.

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A much more efficient solution would be to re-implement the driver to make use of the DMA and be event driven. This example makes no effort to align the start of the buffers, but most hardware will have an alignment requirement. The ST peripheral library Please note that the peripheral library utilised by the demo application is neither re-entrant nor event driven.

The interrupt service routine measures the number of processor clocks that occur between each interrupt – and in so doing measures the jitter in the interrupt timing. LEDs 1, 2 and 3 are under the control of the standard ‘flash’ tasks. Entering the IP address into the web browser obviously use the correct IP address for your system Served Web Pages The top of each served page includes a menu containing a link to every other page.

Ethernet address and network

Remove the reference to the Ethernet buffer from the network buffer descriptor so releasing the network buffer descriptor does not result in the Ethernet buffer also being released.

Only pointers to data were swapped. As this is the simple rather than efficient example the received data will just be copied into this buffer. The MAC address and net mask are configured within the same header file. It runs in a single task so there are no re-entrancy related issues, and it allows a lot to be achieved in a very small RAM and ROM footprint.


The second example demonstrates how to implement a more sophisticated and faster driver. Click here to view a static menu. It might be possible to do this in the interrupt service routine itself, which would remove the need to unblock this task for packets that don’t need processing.

This raises the possibility of problems related to re-entrancy or lack of it. Users must familiarise themselves with the uIP license. In most cases this will just involve calling whichever initialise function is provided with the Ethernet MAC peripheral drivers – which will in turn ensure the MAC hardware is enabled and clocked, as well as configure the MAC peripheral’s DMA descriptors. It is assumed this already exists freedtos is known to work.

For example, if the web browser computer uses IP address If all the demo tasks are executing with their expected behaviour then the check task writes PASS and the maximum measured jitter time in nano seconds to the LCD again via the LCD task.

FreeRTOS+UDP Primer – A Step by Step Tutorial

During its initialisation, the demo application accesses IO port configuration from within more than one task. Permits frerrtos to be sent to the target from a web browser. FreeRTOS’s centralised deferred interrupt handling capabilities can also be used. A simple mouse driver is provided along with the web server demo. If this proves problematic then place the initialisation library calls inside critical sections.


The maximum measured jitter time is latched in the ulMaxJitter variable, and displayed on the LCD display by the ‘Check’ task as described below. Note that vPortEndScheduler has not been implemented. Further lwIP related uploads would be gratefully received. The following tasks and tests are created in addition to the standard demo tasks: Check function – called from the tick hook This only executes every five seconds.

If an alignment is required then the size of each buffer must be adjusted to ensure it also ends on an alignment boundary. This page provides more information on each of these steps, and provides two examples.

On the negative side, lwIP is undeniably quite complex to use at first, but time invested in its use will pay dividends in future projects. The jitter time is ethernt within the high priority interrupt test as described above.

The supplied value of Hz is useful for testing the Freertls kernel functionality but is faster than most applications require. Connect the STMC evaluation board to a computer running a web browser either directly using a point to point crossover cable, or via an Ethernet switch using a standard Ethernet cable.